Ok guys, hope you can help with this one.
BACKGROUND:
I have run a Kenwood PS 400wRMS x 1 bridged @ 4 ohms, 2channel setup for 2 years now. The amp has never given me any problems. I recently bought a Fosgate 700S amplifer off of Ebay. The seller also included original receipt and a Performance Service Plan valid through 2007. The Fosgate is also a 2 channel amp with the spec sheet showing 700wRMS x 1 bridged @ 4ohms. As I'm running a supposedly 600wRMS Power Acoustik 12" woofer, this seemed more appropriate to me than the Kenwood.
INSTALL:
Well the install was simple. I moved the power, remote, ground, speaker cable, and RCAs to the New amp as the old setup was working properly. I wired according to the manual and this was 100% I'm confident. The left and right independent gain dials (with no markings or volt indicators) came from the seller with the left @ 1/4 from the left and the right @ about 1/3 from teh left. I backed the right down (counter clockwise) to match the left gain setting. I couldn't match the setting on my old amp as there were no values on the dial. I figured this 'low' setting should be safe for the initial test. One thing I noticed from spec sheet was the Fosgate asks for a 60 fuse up by the battery. My Kenwood setup was utilizing a 40 with no problems and as I didn't have one on hand, I didn't switch it to a 60. I also enabled the LPF and set it at the lowest setting 50hz as I had on the Kenwood.
RESULTS:
The system fired up as was expected. And it sounded great. Much more powerful than the Kenwood. I noticed that at much lower volume the system was slamming. However, I could also tell that I would need to fine tune the gains/stockEQ in deck/and remote bass controller to find the ideal setting. However, all in all, it sounded great and was better than I had expected.
PROBLEM:
From the initial use, I noticed a faint electrical burning smell coming from the amp. The amp was cool to the touch and I figured that the amp had "sat in the seller's closet for 1 year" so maybe it just needed to get fired up first. As I drove to work today, listening for 15 minutes at high volume, without excessive distortion (although there was some as it wasn't fine tuned), the amp shut down. I checked the inline fuse and it was toast. The burning smell was stronger and I could smell it through the arm rest 'portal' into the trunk even with both front windows down.
PLAN:
I plan on replacing the fuse today. My idea is that if it blows immediately, the amp is shot. If it doesn't blow however, why would the amp be making the burning smell? Is it just toast, and what do y'all think would be the best step from here, regarding diagnosis and replacement/repair (considering the service contract may be valid - although I'm sure BestBuy will only replace based on sale price and at orginal price of $239 there is nothing in that range that can come close to the 700wRMS x 1 that BestBuy sells).
Thanks guys.
Replies (46)
uochronos on 12/30/2004 14:54:02
burning not a good smell dont keep turning it on you well definatly toast it then... we haev alot of good tech people here let them help you narrow down the problem and see if they can help fix it.
Chronos
Victor on 12/30/2004 15:08:49
Well before replying to the original question i wud appreciate the way you have presented this problem to us.. it is a very nice write up which many visitor coming here do not write..
It is nice to have all the story and the details , i wud like to make a point for others to learn from this post and write a detailed explanation so that it is easier for us to help you..
one thing you forgot to mention was the model number for the PA sub you are using.. and if you bought the amp from eBay then why would best buy replace it..lol...anyways everyones prone to mistakes..
please state that..
is the amp running in bridged mode??
and what is the total load the amp is subjected to.??
Victor...
Victor on 12/30/2004 15:20:18
is the sub this one..???
http://www.electronixwarehouse.com/car/sgl-prod/speakers/woofers/pow-acoustik/pabl12.htm
Victor...
eldevioso on 12/30/2004 15:24:20
Well...damn, thought I was thorough ;) but here's the add'l info:
1) the Kenwood PS series amp is model PS-400T or something like that, but that doesn't really matter as THAT amp works properly, and will be going back into action while I figure out the situation with the new Fosgate amp.
2) as for the amp being purchased on Ebay, the BestBuy service gauruntees ARE transferrable as long as the item hasn't already been replaced. The seller provided the documentation and original receipt. Assuming, it has not already been exchanged once, then they will attempt to repair or replace it. Then the question will be whether or not they are willing to give me a comparable amp performance wise, or just cost wise. If its based on sales price (which it probably is), then the Fosgate 700S is going back to seller or I'll have to take it up with Paypal, or worst case, I'm screwed :(
3) The Fosgate700S is running bridged with a 4 ohm load from a single PowerAcoustik 12" dual-2ohm (wired in series) 700wRMS sub. The amp is rated at 700wRMS (bridged) @ 4 ohms. As for the input voltage, I'm not really sure, however, there are no voltage indicators on the gain dials on the Fosgate amp, so it will have to be tuned by ear. . . . . as a note, my last amp, the Kenwood was also running bridged w/ a 4 ohm load.
Thanks for starting the process. . .I might add I'm pretty sure I mentioned this all in the original post, but as it was long, some gets lost in that ;)
eldevioso on 12/30/2004 15:27:20
Here's a link to the sub:
http://www.bestbuy.com/site/olspage.jsp?id=1051384109574&skuId=5344246&productCategoryId=cat03081&type=product
Victor on 12/30/2004 15:59:23
OK..., that sub is a 700wrms sub..
anyways now lets get to the original problem..
1:- fuse near the battery cud have blown .
2:- the amp fuse cud have blown.
3:- improper grounding.
4:- extreme low loads which the amp cannot take.
5:- damage to internal parts of the amp.
All these cud be the reasons for the problem you are facing.
step one. remove the connection of the sub to the amp.
replace the blown fuses if any.
turn on the amp and let it be turned on for quite a while when the car is running as well as when it is stationary. . see if it shuts down itself without any active load on it.
see how much heat it generates without working and does it smell bad still..?? any fumes or smoke??
if this is the situation and you still see problems then there is definitely something wrong with the internal parts of the amp..and you need to win a battle to get it replaced by any e-tailer.
if there is no problem then.. it is thus derived that the amp stops performing when subjected to a specific load ( ie. your sub )
now to check that ..
two things can be wrong here.
wiring and gain settings.
regarding the gain settings .. both the left as well as the right channels shud have similar gain settings..
since both the channels have seperate gain settings it means that the amp uses 2 amplification circuitry to amplify the right and the left channels individually.. there cud be problems here if the gain settings are different on both the channels..
try setting the gain settings at a value at which you HU's output is rated. ( RCA voltage ).
values lower or higher thatn that can either harm you amp speakers or HU in some way.
now the next step..Wiring...
at first check the way you have wired the voice coils of your sub ( may be you have wired them to 1 ohm ie. in paralle rather than 4ohms ie.series .. it is possible that you were lucky to have the kenwood amp survive at 1ohm and u wud have never noticed the big blunder..trust me even i have done that a few years back when i was a child in car audio )
now if the wiring of the voice coils of the sub is right then we now have to check they way we have wired the sub to the amp..
have you wired each voice coil individually to each channel or bridged them and wired the sub to the... {+ve} of 1 ch and {-ve} of the 2nd ch..?
try going thru all over it ( wiring ) again..
if it works out you sure have gone wrong somewhere in the installation.. if it doesnot .. the only option would be replacing the product..
Let us know before you buy the replacement.. so that we cud help you select an appropriate product for the application.
Victor...
Ps:- digital monobloc amps are much more efficient and reliable for subwoofer applications.. plan on buying one if you got the worst luck and dont get a refund or replacement..
Victor on 12/30/2004 16:03:40
here is a .pdf file from Power acoustik..
it shows the way the sub should be wired for different kinds of load..
look at the way they have wired it for a 4 ohm load and cross check it with the way you have done it.. i suspect wiring as the only big problem besides internal damage..
Victor..
Victor on 12/30/2004 16:05:48
hehe.... i forgot to paste the link... i do this a lot..lol..
ok .. here it is..
http://poweracoustik.com/SUPPORT/MANUALS/PA-FUBRWoofer.pdf
Victor...
Victor on 12/30/2004 16:10:14
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&category=39737&item=5740713518&rd=1
is this the seller you got it from???
Victor...
eldevioso on 12/30/2004 17:54:59
Thanks for the links. And no that's not the seller. I bought from an individual not an e-tailer. However, he is being cooperative thus far on the situation. As for the issues:
1) I wired the voice coils in series, by jumping the positive from coil 1 to negative of coil 2. Then I ran a wire from the available remaining positive and negatives to the wiring block on my box. The diagram in the .pdf supports this. However, I will check the load again with a multimeter to make sure that this is the case, and if not I'll fix that. In regard to the speaker, its worth noting that the box is built to spec within 0.02 cu feet I would say, including port #, size, and length (just in case that helps).
2) I will definitely try the "no-load" testing method. Hopefully sometime tonight or tomorrow as I have the day off.
3) As for the list of possibilities, the fuse near the battery DID blow. That's why it shut off. However, I'll need to try the no-load test to see if there is some problem internaly (which I suspect there is). Further, there is no fuse built into the amplifier (unless I overlooked it - and I'll double check). The ground is good, as it was working before and hasn't been altered, and is securely fastened to the new amp. I'm confident the load wasn't an issue, but like I said, I'll double check to be sure.
So, that leaves us with either a fluke short in the fuse by the battery or internal amp problems. In this regard, would the fact I was using a 40 fuse instead of the recommended 60 fuse come into play?
4) As for matching the gain to the HU, I could use some help here. It is my understanding that you can use a multimeter to read the input from the HU from the RCA's. Yet, since the Fosgate doesn't have markings on the gain dials (ie...there is nothing to say what voltage you're setting it to, it simply has an arrow pointing in the direction) how can I determine what voltage the amp is set at so that it matches the HU. Can I measure somewhere, like the speaker output?
..and as a final note, the speaker is wired in bridge mode as you described. With the voice coils in series (to be double checked ;) I'll let you know what I discover and we can go from there.
Victor on 12/30/2004 19:14:20
wow.... those links made this post a very lenghty one...hehe.. i mean in actual page width....hahahaha
hey if you are around.. why dont u join in the chat room.. its much easier to deal with such problems in there..
Victor..
admin on 12/30/2004 20:31:17
Ok.. after checking everything let us know the details of how you checked and what results did u derive..
regarding the fuse in amp.. all the amps.. have a fuse.. it is the basic saftey measurement for all the car audio amps.. so the possibility of a fuse not being there is not even 1 in 10000.. but the RF amp models after 1993 stopped providing user servicable parts.. and have incorporated the fuse on the main board itself..
read this page..
http://rockfordfosgate.com/scripts/rightnow.cfg/php.
exe/enduser/std_adp.php?p_sid=Z_Nonjuh&p_lva=&p_faqid=41&p_created=
948148912&p_sp=cF9ncmlkc29ydD0mcF9yb3dfY
250PTE2
JnBfc2VhcmNoX3RleHQ9Um9ja2ZvcmQgRm9zZ2
F0ZSA3MDBTJnBfc2VhcmNoX3R5cGU9MyZwX3
Byb2RfbHZsMT05JnBfcHJvZF9sdmwyPX5hbnl_Jn
BfY2F0X2x2bDE9MSZwX3NvcnRfYnk9ZGZsdCZw
X3BhZ2U9MQ**&p_li=
replace all the blown fuse before you go ahead.
read the following links too..
http://rockfordfosgate.com/scripts/rightnow.cfg/php.exe/
enduser/std_adp.php?p_sid=Z_Nonjuh&p_lva=&p_faqid=43&p_created=
948817670&p_sp=cF9ncmlkc29ydD0mcF9yb3dfY
250PTE2JnBfc2VhcmNoX3RleHQ9Um9ja2Zvcm
QgRm9zZ2F0ZSA3MDBTJnBfc2VhcmNoX3R5c
GU9MyZwX3Byb2RfbHZsMT05JnBfcHJvZF9sdmwy
PX5hbnl_JnBfY2F0X2x2bDE9MSZwX3NvcnRfYnk
9ZGZsdCZwX3BhZ2U9MQ**&p_li=
http://rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser
/std_adp.php?p_faqid=46&p_created=950313207
dont forget to read the above links in detail.. shud prove very useful.
Victor..
danielm87 on 12/30/2004 21:05:01
I have personally been in a similair situation that this guy has been in. I replaced my old amp and subs with bigger ones, and quite unfortunately, and unitelligently, was using a 20A fuse on the power cable, running 600 watts to two subs. Needless to say, whenever the HU's volume level went to the halfmark point, that 20A fuse blew.
I assume not too many people have adressed this situation, but i beleive that you should ALWAYS have a perfectly appropriate fuse for the current draw your amp is taking from your car's charging system. Victor and everyone else have given you proper instruction, but MAKE SURE you get a 60A fuse (or better) on that power cable going to your amp, and pray to God that your amp is running okay internally.
You would do well to catch Swez or Vic in the chat room, it really speeds things up if you have a problem and need an answer quick.
I hope you work all your problems out with this situation and have a Happy New Year!
~Daniel Myers
swez on 12/30/2004 21:07:32
Hummmm, that burning smell troubles me too... What gage wire are you presently using here for the main power line? (hope you say #4 gage here) Good to see you back at CK!
After you replace the BAT fuse, if the amp works and all is well, you can check the voltage out from amp to sub with an AC volt meter. Using Ohm's Law, use sq. root of (Watts x Ohms) to determine volts output from amp to sub. I would anticipate close to 50 volts of signal from the amp at 700 watts into a 4 ohm load. That's about 13A of current as well. Use a #12 gage speaker wire from amp to box to sub min.
Your actual voltage readings may vary as most meters read RMS volts and the load (sub impedance) will vary with frequency. A sub wired at 4 ohms (nominal) will read about 3. 4 ohms off a DC ohmeter. However, when in action the impedance can go substantially higher than 4 ohms near Fs of the sub.
In all, I hope the new RF amp is OK and all you have to do is readjust the gains a tad. Double check your wiring for melting or scorch marks. Hopefully, the main power wire did not short to ground, hense blowing that 40A fuse. This RF amp can pull some serious current as it is a Class A/B amp. (700/13.5 = ~52A RMS... almost 90A peak draw)
Good luck and let us know what you find out OK?
Swez
eldevioso on 01/2/2005 17:03:07
Glad you remembered me Swez. It has been awhile but this is definitely the first place I turn to when I have a problem.
As for the power wire from battery to amplifier, I wanna say its 8 gauge, yet this is definitely the maximum size the RF amp can accept as I could barely get the wire inside the connector terminal. Also, I'm pretty sure the power wire didn't ground out, as it wasn't moved at all from teh old installation (ie. no tugging, no pulling no nothing). However, I will check it when the whether clears, as I don't have an appropriate work facility when its raining ;)
As for the draw of the amp, it was substantially higher than the Kenwood as I noticed the lights were dimming while the car was running which never happened with the older amplifier. That's antecdotal, but I know its pulling hard from teh electrical system.
So here are some new questions:
1) Given that you say it draws roughly 50A and peaks at 90A, is there a benefit to having a very large fuse up front, or would it be safer to keep it at 60A?
2) Thanks for the writeup on the voltage measurement. However, I would like to figure out how to properly set the gain. I mean, I can measure the signal coming from deck, but hte RF has no markings on the dial. Since I don't have advanced equipment, am I reduced to using the "ear" method to set them?
3) In regard to the gain settings, I had them at only 25% from teh left. Is it possible that I should have to back them all the way down to the left? If so, what signal voltage measurement should I expect to find requiring the gains to be set all the way down?
Thanks in advance. And an update before Ive had a chance to tinker with it, is that Best Buy still services this amp, and said that they will rebuild it for me, assuming something melted internally (which must be the case as teh smell didn't go away for 3 days). So I will have all new internals, which will be nice :) I'll keep yall posted.
swez on 01/2/2005 22:19:41
A #8 wire kit is really pushing it if you have 60A+ pulling from the amp. That burning smell, may be the amp, or it could be the power line insulation heating up???
Gain settings are to match up with HU output voltage. If you have a min of 250mV (1/4 volt) and max of 4.0 volts, the HU output should match close to amp gain settings. Harder to do by ear, but if your gains are set too low (say 2.0 volts) and the HU puts out 4.0 volts, amp reaches max power at ~2.0 volts and lower input setting clips amp badly.
Better to get out the tech manual for that amp and determine the proper gain settings from HU with an AC voltmeter at amp inputs. (10Kohm load resistor)
What is the full part # of that amp?
Swez
CSR on 01/3/2005 11:50:52
I dealt with something very simular to this story, just last weekend. A freind of a neighbor did the same thing. He had a 200 to 300 watt amp pushing a 12" sub and replaced the amp with a 700 watt unit. Same story, same results. The 8 gauge wire he had for the old amp couldn't power the new amp and fried it. He got that replaced and we installed it with a new power line and fuse. I asked if the sub was rated for that much power and he said it could handle twice that. After he got home he gave me a call and said he blow his sub. Next weekend, we'll install a new box with better speaker wires. Sometimes you just need to check things out yourself. After a few phone calls, I had him bring his car over so I could see what the problem was. 3 nights of phone calls vs. 40 sec of looking at the car to figure out what the problem was.
eldevioso on 01/3/2005 17:49:58
The full part number is: Rockford Fosgate "Punch 700S" and the .pdf file is here:
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/fattach_get.php?p_sid=FVNnaEuh&p_tbl=9&p_id=278&p_created=1083252061
but it says there in the .pdf that the terminals will "accomadate up to 8AWG." This makes sense as I couldn't possibly shove a fatter wire into the block.
However, would I benefit by running a fat 4 AWG cable back from the battery into a distribution block, with an 8AWG going from tehre to the amp. Ultimately this may be necessary as I want to hook up the old Kenwood to run my highs.
Unfortunately all the manual says about gain settings is that you can configure them will an oscilloscope. Well I don't have access to one. But I do understand teh gist of gain settings. That's why I had mine set "high" (from your description) or at the setting that makes the least power for the same input signal. I will measure the input signal for sure and relay that to yall. But, even then there are NO markings on the amp to tell me what voltage the gain dials are set at.
As for the burning smell, its definitely coming out of teh amp. I mean, its been a few days now with the amp off teh entire time and you can still smell the remnants from the vents of the amp. I will visually and olfactorily ;) inspect the wiring in addition though.
swez on 01/3/2005 23:43:38
If you are planning to add a 2nd amp soon, definitely upgrade to a #4 power line from BAT to a D-Block. From there, can use the #8 wire you have now, to power each amp.
Sounds like the "Magic Smoke" was let out of that RF amp. If it still works... good. If not, need a trip to the repair shop or swap it out for a new unit. But if you do swap it out, definitely use a Class D sub amp as they draw less current for the same wattage output.
You may get lucky and just peel off the cover plates and look inside the amp. Your eyes and olfactory sensors will tell where the problem lies. My guess, this amp pulls too much current and the problem happened at night? (lights & heater on?) If that was the case, voltage from the electricals may have dropped to a point where the amp lost voltage and wound up pulling excess current to meet output demand.
Swez
PS Gain settings may be a factor here too. Without accurate markings, are flying blind. When we don't know what gain settings to use, midpoint is usually a good place to start.
Victor on 01/4/2005 01:36:06
I feel Its ridiculous for a company like RF to not provide markings on the gain settings..
Victor..
uochronos on 01/4/2005 03:50:25
unfortunatly victor there are very few amps with accurate gain numbers even... my phoenix gold amp is the best one i have personaly used it has 4 markings on it and are relativly accurate most other amps i have used though only show the low and the max and one in between. even then though using your ear to set it without distortion is better then trusting the markings which usualy are off a bit.
Chronos
Victor on 01/4/2005 05:37:04
wow... its really surprising.. cause most of the brands i have sold.. Sony..Blau..Pioneer..many Alpine..some Polk some JVC some Kenwood all of them have gain settings all marked with appropriate voltage ratings at 4-5 stages..
( if you are pointing on their accuracy then i would agree with you that they may bot be as accurate as mentioned.. but as far as the marking is concerned i have seen them on most of the amps i have sold till now..)
Victor...
eldevioso on 01/5/2005 00:48:26
**UPDATE**
Well yesterday the rain let up and I was able to yank the amp outta the car. I took it to the BestBuy technician who bench tested it and said that it was Okay. Perplexed, I had him come out to the car and measure the ohms of the sub as it was wired. Too my shock it was showing 2 Ohms!!!
I couldn't understand how that could've happened. Since, the speaker is a dual, 2ohm voice coil setup, that didn't make sense. The tech, and his supervisor, rudely informed me that BestBuy has never carried a dual 2ohm voice coil sub and that I had unknowingly wired dual 4ohm coils in parallel. Well that did it for me and I knew they were full of crap. As you can see in the link from BestBuy's web page for my speaker, that I was correct about the coils and I had wired them in series.
Well, I went ahead and bought a 60 A fuse holder and fuse, and spliced it inline by the battery. I reconnected the amplifier, backing the gains all the way down. When I did this I realized that they were at 75%!!!!! from full clockwise. Unbelievable!!!! The arrow was pointing at 9 o'clock, and I turned it counter clockwise. It kept turning to 8, 7, 6, all the way to 2 O'CLOCK!!! So at full minimum on the gain, the damn thing is pointing to the right! Wow, everyone should take note that the left side of the dial doesn't necessarily mean its at its lowest setting.
So I backed the gains ALL the way down and disconnected the speaker from the amp. I ran the system for a few minutes and the fuse remained intact and the amp wasnt' smelling. Then I turned off stereo, and reconnected the speaker. I immediately found that the speaker was blown. Then it dawned on me, that one of the voice coils must've blown. That's why it was showing 2ohm rather than 4ohms, as it should in the configuration I wired it in.
Today I removed the sub from my tube, and checked the ohms of each coil. Sure enough, one of them was 1.8ohms, and the other had no reading. There was my answer. Furthermore, I noticed that the burning smell wasn't coming from the amp, although I was sure of it, it was coming from the speaker!! I also noticed the single 12AWG wire that I had bridged the coils with was smoked and smelled like crap. So I returned the sub and exchanged for a new one.
This time, I bought some new 12AWG cable and rebridged the new sub. Rewired the tube, and checked ohms. 4.2 ohms. This I took as a good sign. And reconnected it to the system. It played fine. I then slowly adjusted the gains from 2 o'clock to about 6 o'clock on the dial. I then adjusted deck bass controls and remote bass control (remote to about 66%) and it sounds good. It definitely doesn't hit as hard as it was before I blew the sub the last time, but I'm sure that has something to do with the gain settings having been 25-30% higher before.
Sadly, I noticed a little bit of the burning smell again, and this time the amp was warm, but the smell went away. I tried to measure the AC Voltage coming in on the RCAs with them disconnected from the amp, and the system on low volume, but the measurement was ranging from 1-10V. Unless I had the multimeter setting wrong (which I might), I don't know if I'm measuring this right. It seemed to peak as the song that was playing changed.
1) How do I check the signal voltage from the RCAs? What multimeter settings and should the stereo be on or off?
2) Would it be worth while to go and have a reputable shop tune my system...as I think I should be able to safely get a little more performance out of the amp.
3) Is it possible that one of the channels inside the amp isn't performing as well? It is running in bridged mode, but my thoughts are if one of tghe channels is toast or on the way out, then bridged performance would suffer as well.
....thanks for all the help guys.
Victor on 01/5/2005 02:20:52
This is what Rockford Fosgate has to say about Gain settings..
Question
How do I set the gain and bass control levels on my amplifier?
What are the right settings for the gain and bass controls on my amp?
Answer
Correctly setting the Gain controls on your amplifier is easy if you have some signal test discs and an oscilloscope! But, if you don't happen to have those available, then you may have to do some common-sense guesswork to "dial-in" your amplifier.
The Gain control is NOT a volume control! The gain adjustment (or control) is a level-matching control that adjusts the amplifier to work with the electronic piece(s) used before the amplifier. This piece before the amplifier could be the head unit, an EQ, or a crossover, and you set the gain control on the amplifier to match that unit's pre-amp voltage level. You can find out the unit's preamp output level in the owner's manual for that unit, as most manufacturers know you need this information in order to set up your system.
Essentially, by dialing-in the gain control, you're telling the amp how much signal you're putting into it so the amplifier will reproduce the signal accurately. If you have the gain set too high, the amp will make full power right away, and you'll have problems with distortion and "clipping". If the gain is set too low, the amp may still make full power, but it might not sound as loud as it should, and you'll think you aren't getting much volume. Our amplifiers are capable of accepting a signal input level from 250 millivolts to 4Volts, and you change the sensitivity by adjusting the gain control clockwise (more sensitive for low-power decks like 1-Volt units) or counter-clockwise (less sensitive for high-powered decks like 4-Volt units).
Since we do not put "indicators" or markings on the side of the amp to indicate gain levels for specific input voltages, this is where you will have to do a little "educated guessing" to set the controls up correctly. An oscilloscope's signal-measuring capabilities would come in handy right about now, as you could read the output levels of the amplifier while playing test tones (like a 1KHz tone) to determine at what point your amplifier "clips", and that's where you stop turning up the gain control.
But, if you don't have any of this cool stuff, then you'll have to assume the gain control is like a progressive-gain dial that becomes more sensitive as you turn it up (clockwise). We usually tell people that if they have a 4-Volt head unit, turn the gain all the way down (counter-clockwise); if they have a 2-Volt head unit, turn the gain 1/3 of the way up (clockwise); if they have a 1-Volt head unit, turn the gain 2/3 of the way up; and for 500mV decks, turn the gain 3/4 of the way up. While these suggestions are buy no means 100% accurate, they will work fine most of the time. When in doubt, have a professional double-check your work.
As far as the Punch Bass control goes, setting it correctly is a matter of both personal preference and the type of enclosure you are using for your speakers. If you are using your amplifier with a speaker (or set of speakers) that are loaded into sealed enclosures, then generally we recommend setting your amplifier's Bass control no higher than 1/4 of the way up. If you are using a ported enclosure for your speaker(s), then we generally recommend setting the Bass control no higher then 3/4 of the way up. Because the Punch Bass control is really an equalizer, you should not use it if you already have an EQ hooked up to your system (unless your EQ does not cover frequencies below about 70Hz).
If you're unsure of the best way to set up the gains or bass controls on your amplifier, we recommend you seek the assistance and advice of your local Rockford Fosgate dealer. They have the knowledge and equipment necessary to be able to set your gear up right!
Victor...
Victor on 01/5/2005 02:37:15
This explanation has really Pi$$ed me off..
The worst effort I have seen by a reputed company to back their stupid acts..
a whole bunch of $hitty ways to set up the gain settings and bass control....
" educated guessing" hahahahahahahaha....lol.. as if guys who use the RF amps are a bunch of uneducated guys...
hehehehe...so if you dont want your amp to clip and distort u gotta buy an oscilloscope and testtone disks... or do " educated guessing"...lol..
and then they write something like this..
"While these suggestions are buy no means 100% accurate, they will work fine most of the time. When in doubt, have a professional double-check your work"
and
"If you're unsure of the best way to set up the gains or bass controls on your amplifier, we recommend you seek the assistance and advice of your local Rockford Fosgate dealer. They have the knowledge and equipment necessary to be able to set your gear up right!"
a nice way to make the RF dealers earn more just from doing minor tweaking like this... leave aside the price for installation..
so if one buys an RF amp he spends more time and money in setting it up right than the amount he spend in actually buying it..haha
Its disgusting..
Victor...
eldevioso on 01/5/2005 03:05:11
Yeah, i hear you on that. I've read that link three times now. It's pretty much worthless, as I'm still unsure if I've done it right. Although I did what they say. it really sucks, but hopefully teh experts here have a better solution for me. If not, I'll got the local shop that has helped me a lot with verbal troubleshooting. I'm sure they wouldn't charge me much at all.
swez on 01/5/2005 12:07:43
Hummm, I can see the frustration mountion in Victor... take a chill pill dude! Please edit your *&@#!!. TY
The RF explanation leave a lot to be desired for sure. But, the general idea is to match the HU voltage rating (70-80% max power) to the amp input stage. Most amps have a 10,000 ohm imput impedance. To get an accurate HU voltage reading, we need a patch cord with a 10Kohm load. The voltage is read off the terminal ends of the resistor. (AC volts)
Have a look: http://www.bcae1.com/gaincon2.htm
Really, it's not as hard to do by ear as one might think. But we have to train our ears to detect distortions and clipping. This is very difficult to do at high SPL levels. (above +90dB) Why? Because our ears get saturated with high SPL audio and begin to go into a "self-protect" mode triggered in the brain.
Note: Ever been to a loud concert and came out feeling drunk and disoriented? (but did not drink or "smoke" before the concert) Ringing in the ears are also common if we get too close to main speakers as well. The brain has determined our ears are getting too much input and
shuts that part of the brain down.
Finally, when we are tweaking for max clean SQL, we open the doors and step back from the vehicle and listen from a distance. It will still be loud inside the car, but as we walk about th rear of the vehicle at 10 feet or so, we can get a pretty clear indication of clipping VS clean audio signals.
Hope that helps,
Swez
eldevioso on 01/5/2005 13:59:43
Lets hear some more detail on the patch cord Swez...
uochronos on 01/5/2005 18:16:00
just a note here to have a shop set your gain for you usualy costs like maybe 20$ i think the local place i sent a buddy to when he asked for a good place to set up his amps only chared him 20$ and they set his gains and LPF and setting on HU for him and it came out sounding great. took the guy all of like 20minutes or so from what my friend said.
so RF saying to have a profesional do it is a good idea. infact i think my phoenix gold amps warranty is contengent on the amp being installed and set by a authorized dealer. and i knwo many other companies are like that althuogh they dont seem to uphold that rule often.
Chronos
swez on 01/5/2005 22:32:53
PATCH CORD:
An RCA connector on one end, with a 10Kohm resistor between the ground and center lead. We take our voltage readings off both ends of the load resistor.
Gnd.........X.wwww.X..........Center lead off HU.
X = probe locations
Swez
eldevioso on 01/13/2005 12:29:33
Just to make absolutely certain I have this right.
I purchased:
(1) Female/Female RCA jack.
(1 pack) 10K Ohm Resistors
(1) Spare RCA Cable
Here's what I think I'm supposed to do:
1. Plug F/F adapter into one of the signal RCAs coming into my amp.
2. Cut Spare RCA cable and plug male connector into the 'empty' end of the F/F adapter.
3. Attach one end of the 10K Resistor to the positive signal on the 'SPARE' RCA cable that I cut and connected.
4. Attach other end of the 10K Resistor to:
....a. The ground lead of the same "SPARE" RCA cable?
....b. Another ground on the chassis of the car?
5. Then measure from each end of the resistor?
Here's how I envision it:
HU-------o- (F/F Adapter) -o--(spare RCA 'cut')---X---ccc10Kccc---X--Ground
X= probe locations
ger_10 on 01/13/2005 13:53:21
is ther any one who could help me on my topic iam desperate for help..reply at wiring for car please
eldevioso on 01/13/2005 19:09:18
Jeez!!!
Please don't hijack my thread. Simply wait for a response, as people WILL get to your question with 24 hours without a doubt. Or go to the Chat and see if you can find an instant response. Don't post in other's threads, unless its ON topic.
Thanks.
Victor on 01/13/2005 19:48:04
cool down guys.. well wldevioso.. things like this happen.. its all due to frustration of not getting a response and also because he has problems with his system.. such frustration has crept in all of us during our early days in car audio.. take a chill pill..
As for you ger_10 how would u expect a quick response from anyone when you have not given complete details of your HU.. model number.. the wires on it and the wires in your car harness.. And anyways UK has already given you a very list of what colour wire goes where..
U are simply amazing UK.. never expected anyone to remember car specific colour coding.. thata a very nice explanation u gave him there.. keep it up..
Victor..
UKinstaller on 01/13/2005 19:53:51
that's pretty much my specialty at my work is hardwiring radios. i work in an area where many stereos are stolen and the goofy thieves cut the harnesses instead of unplugging them. seems to me like it'd be easier to unplug!! thanks though.
-UK
swez on 01/14/2005 06:11:32
Hummm, little squabbling here eh? Children... behave! LOL
Elde,
You have proper patch cords and hardware now. The hookup scheme is as you have noted and the grounding point to test, is the ground side of the RCA cable. That is your reference ground source. Your test fixture will look like this:
1. HU=======(f/f jack)=====RCA wire to 10Kohm resistor.
2. RCA test kack======(Center lead)------*(10K resistor)*------to shielded (ground) wire on test jack. The (*) denotes probe locations.
Note: The RCA cable has 2 wires. One is a braided ground and the center wire is Pos signal connection. The 10K resistor will be installed as you noted above. I have tried to amplify that idea in my diagram.
Once you have all this hooked up, probe the resistor with an AC volt meter scaled at 1-10 VAC. Turn on the HU, dial it up and measure the voltage at either end of the 10K resistor. That will be your HU output voltage. Got a number.... match gains on amp to that voltage reading.
Would anticipate a HU RCA reading between 2-5 volts.
Finally, when adjusting gains on amp, imagine a clock face type thing here. Mid point is say 12:00 position and a good place to start adjustments. Depending on the amp, as you move toward the 9:00 position the amp/sub may get louder (it may get quieter). This is the sensitivity aspect of the gain controls.
Note: In this case, max sensitivity is 250mV (1/4 volt) Min sensitivity is 6 volts per RF manual.
Anyway, start at 12:00 position and move gains to 9:00 and then 3:00 positions. The power to the sub will change dramatically as you sweep from 3:00 to 12:00 to 9:00 positions. The proper setting will be loud, yet distortion free with your HU volume settings at 60-75% of max.
Make sure your HU tone controls are set to flat. (0 boost or cut). Use no bass boost on the amp at this time either. Once you have the amp dialed in to produce full yet clean bass, you can measure the AC voltage at the sub input terminals. It should read pretty close to ~53 Volts AC when amp is at 700 watts output power, to a 4 ohm load.
FYI: You may find the speaker voltage readings are slightly higher or lower than 53 VAC. This is normal as inductive impedance (dynamic resistance) of the coils will change with frequency. However, if you see a huge variation in voltage... something is a bit off.
Whew... this is a lot of blabbing huh. Dang, I hope it helps!
Swez ><>
eldevioso on 01/18/2005 20:44:35
Ok..I think I understand. So the RCA test jack cable will be plugged into the F/F Jack. then I will cut the cable and attach one end of 10K resistor to the center wire (+) and the other end of the 10K resistor, looped back onto the braided (-) shield that encompasses the center wire.
Is this correct?
If so, I'll try this sometime soon and let ya know the results. Thanks a lot.
MrBrownstone on 01/19/2005 01:02:02
Burning smell, previously used amp. Refurbished is likely if smell is from AMP
eldevioso on 01/21/2005 17:42:35
The burning smell turned out to be from the first two woofers I've tried in this setup now. I'm on the third, ( a kenwood 400w RMS 12) and it seems to be holding up surprisingly. I'm using that as a fillin until i can assure myself amp is OK and that gains are set properly.
swez on 01/21/2005 22:59:40
Maybe we are barking up the wrong tree here guys. Blown sub #2? Is this a ported enclosure? It would seem so. The PA subs are designed for high SPL and decent SQ. However, if the PTF (Port Tuning Freq) is high for this enclosure, you can fry a sub in short order with high SPL bass notes, below PTF. Why? At PTF (and below), the sub does not motivate very well. It cannot cool the coils adequately and as a result... fried coil(s)
Say more about that enclosure as I am beginning to think the amp is not the issue, nor the sub. It may just be the enclosure is tuned wrong for your PA sub.
Swez
eldevioso on 01/25/2005 15:09:06
Swez-
I feel you may be right about the enclosure. However, I still would like final confirmation on the construction of the input voltage testing rig we were discussing. This is vital for me to know for this and future installs.
As for the enclosure, we discussed this one evening in chat. We came to the conclusion that I needed a HP Subsonic filter at about 35 hz. However, for educational purposes, for the rest of our community lets reiterrate.
ENCLOSURE SPECS:
-Custom 'self built' tube design with woofer on one end of cylinder and port 'centered' on rear end of cylinder.
-Ported enclosure with single 4" diameter 10.25 or 10.5" long port placed directly behind woofer, centered on rear wall.
-Dimensions (recalled from memory): 26.25-26.5" long w/ 14" inner diameter. Calculates to 2.22 cu. ft. based on the displacement of a Cerwin Vega 124 12" Single Voice coil that it was built for. (Note: Vega was many years old and finally gave out after playing trouble free for a long period).
**Using this information and the speaker specs from the PA sub, Swez calculated the PortTuning Frequency (PTF) to be either 32 or 38 hz. if I remember correctly**
As a final note, I am currently running this speaker, as BestBuy was out of the PA subs when I went back for #3.
http://www.bestbuy.com/site/olspage.jsp?id=1072284520697&skuId=6255161&productCategoryId=cat03081&type=product
This is temporary and I do not want installation advice on this sub as the output is dirty and I am unhappy with it altogether. Please advise on the PA sub. ***HOWEVER*** this 200wRMS Kenwood sub, in a 2+ cu ft. ported enclosure although it was designed for a sealed 1 cu ft. enclosure has run fine with no problems, no matter HOW hard and HOW much distortion I send it, with the EXACT same setup as the PA sub. Kinda funny eh?
swez on 01/26/2005 19:16:50
Have taked to an "expert" (my brother ... Swez #2) about this one a bit more and came up with some interesting feedback.
Dale mentioned that a sub in a larger ported enclosure will "unload" below PTF. He confirmed what we already discussed in that area. However, he mentioned that when the sub "unloads" it has a tendancy to reach and exceed X-max a lot faster, below PTF. This creates undue stress on the mechanicals of a given sub and failure is usually a given under high SPL conditions. Most times, the failure is damage to motor mechanicals. Especially high excursion subs with large X-max numbers.
Chances are good, your 2 PA subs failed as a result of lead in wire (tinsel leads) being overly stretched and pulled the voice coil connections apart. An autopsy of the failed subs would no doubt confirm this. The result is the same... one coil set will fail and give no resistance reading in this type of failure.
Your new Kenwood sub probably has far less X-max travel and only 1 coil of 4 ohms. It probably does not like the larger enclosure very well as it is larger than recommended. But, if you keep the power to it under control, it may survive the X-max issues due to stiffer suspension componets... but at high continunous power, the coil may fry before the suspension and motor assy fails.
The best you can do to keep it working, is to go easy on the SPL output of this sub. It's only rated at 200 Wrms. Yes, if the sub motivating well, it will cool the coil better... but if a large amount of clipping or mechanical distortion is present... it too will fail in time.
In short, if/when you get a new PA sub, change the enclosure airspace and perhaps, move the SS filter to a higher number. Dale suggested that if you are tuning to say 36 Hz., a 3rd or 4th order filter (18-24dB/octave filtering) here, will perform much better than a 2nd order filter. (12 dB/octave slope) If you don't have anything better than a 2nd order SS filter, better to raise the frequency it begins to roll of at. (say 50 Hz., rather than 36 Hz.
Comments?
Swez
eldevioso on 01/26/2005 20:41:06
Alright! This is interesting stuff! Here's a question for ya though. If the PTF is say 36hz, that is the tone that the enclosure produces correct? Well...if I use a 50 hz ss filter won't that cut out the optimal frequency of the enclosure or am I seeing this wrong? guess it doesn't matter as my amp's LPF is set at about 60 anyway.
And swez...please take one last look at my final message about the Voltage tester...i really wanna make sure i do that right and have that for the future.
BTW Here are my plans that I'll update yall with:
1) Have amp bench tested by someone knowledgable.
2) If amp is OK, try to utilize the proper SS filter.
3) Test the incoming voltage from head for future reference.
swez on 01/27/2005 12:44:24
You got it.... a proper bench test will consist of:
1. a sign wave generator (test tones, "0" dB ref)
2. a 2 channel O-Scope (to measure and view incoming/outgoing) signals
3. a dummy load (non-inductive resistor)
4. AC voltmeter
Your RCA voltage test jig is correct as well. Most amps have a 10Kohm input impedance for a load. The 10K resistor emulates that load.
SS filter.... in most cases, if we have a target cutoff point at say 36 Hz., a -12dB filter set at 50-60 Hz., will be ~8-9dB down at 36 Hz. You will have some low end bass, but it will help protect the sub from too much power below PTF. The higher the order of the filter, the steeper the cutoff slope will be. With one of these filters, one can roll off the power below PTF very efficiently.
In Pro installs, we have learned to use 3rd or 4th order SS filters (18-24dB filtering) along with "anti-clipping limiters" (clamping circuits) that provide the ultimate in subwoofer protection. This way, the DJ has no ability to go beyond a preset limit on SPL (presets) from the system and will not blow out expensive drivers. We use limiters on all amps that feed Tweets, MB, Mids & Subs. These are expensive active filters, but in the long run, they save a lot of blown driver issues and fried amps.
Some DJ's are NOT the sharpest tools in the tool box. So, we have to "dummy proof" the system as much as possible. LOL
Swez
eldevioso on 10/20/2005 22:17:30
Well....I never did get to much extensive testing, but that damn Kenwood sub is still taking the beating....and I've come to enjoy its sound, just had to back the deck's bass setting down a little more than other speakers, but all in all its ok....
However, now i have some JL 12w3s...so I'll be happy about those, when yall respond to my latest post ;)
swez on 10/21/2005 09:50:39
Got a wiring plan for you on your main post.
Welcome back,
Swez
BACKGROUND:
I have run a Kenwood PS 400wRMS x 1 bridged @ 4 ohms, 2channel setup for 2 years now. The amp has never given me any problems. I recently bought a Fosgate 700S amplifer off of Ebay. The seller also included original receipt and a Performance Service Plan valid through 2007. The Fosgate is also a 2 channel amp with the spec sheet showing 700wRMS x 1 bridged @ 4ohms. As I'm running a supposedly 600wRMS Power Acoustik 12" woofer, this seemed more appropriate to me than the Kenwood.
INSTALL:
Well the install was simple. I moved the power, remote, ground, speaker cable, and RCAs to the New amp as the old setup was working properly. I wired according to the manual and this was 100% I'm confident. The left and right independent gain dials (with no markings or volt indicators) came from the seller with the left @ 1/4 from the left and the right @ about 1/3 from teh left. I backed the right down (counter clockwise) to match the left gain setting. I couldn't match the setting on my old amp as there were no values on the dial. I figured this 'low' setting should be safe for the initial test. One thing I noticed from spec sheet was the Fosgate asks for a 60 fuse up by the battery. My Kenwood setup was utilizing a 40 with no problems and as I didn't have one on hand, I didn't switch it to a 60. I also enabled the LPF and set it at the lowest setting 50hz as I had on the Kenwood.
RESULTS:
The system fired up as was expected. And it sounded great. Much more powerful than the Kenwood. I noticed that at much lower volume the system was slamming. However, I could also tell that I would need to fine tune the gains/stockEQ in deck/and remote bass controller to find the ideal setting. However, all in all, it sounded great and was better than I had expected.
PROBLEM:
From the initial use, I noticed a faint electrical burning smell coming from the amp. The amp was cool to the touch and I figured that the amp had "sat in the seller's closet for 1 year" so maybe it just needed to get fired up first. As I drove to work today, listening for 15 minutes at high volume, without excessive distortion (although there was some as it wasn't fine tuned), the amp shut down. I checked the inline fuse and it was toast. The burning smell was stronger and I could smell it through the arm rest 'portal' into the trunk even with both front windows down.
PLAN:
I plan on replacing the fuse today. My idea is that if it blows immediately, the amp is shot. If it doesn't blow however, why would the amp be making the burning smell? Is it just toast, and what do y'all think would be the best step from here, regarding diagnosis and replacement/repair (considering the service contract may be valid - although I'm sure BestBuy will only replace based on sale price and at orginal price of $239 there is nothing in that range that can come close to the 700wRMS x 1 that BestBuy sells).
Thanks guys.
Replies (46)
uochronos on 12/30/2004 14:54:02
burning not a good smell dont keep turning it on you well definatly toast it then... we haev alot of good tech people here let them help you narrow down the problem and see if they can help fix it.
Chronos
Victor on 12/30/2004 15:08:49
Well before replying to the original question i wud appreciate the way you have presented this problem to us.. it is a very nice write up which many visitor coming here do not write..
It is nice to have all the story and the details , i wud like to make a point for others to learn from this post and write a detailed explanation so that it is easier for us to help you..
one thing you forgot to mention was the model number for the PA sub you are using.. and if you bought the amp from eBay then why would best buy replace it..lol...anyways everyones prone to mistakes..
please state that..
is the amp running in bridged mode??
and what is the total load the amp is subjected to.??
Victor...
Victor on 12/30/2004 15:20:18
is the sub this one..???
http://www.electronixwarehouse.com/car/sgl-prod/speakers/woofers/pow-acoustik/pabl12.htm
Victor...
eldevioso on 12/30/2004 15:24:20
Well...damn, thought I was thorough ;) but here's the add'l info:
1) the Kenwood PS series amp is model PS-400T or something like that, but that doesn't really matter as THAT amp works properly, and will be going back into action while I figure out the situation with the new Fosgate amp.
2) as for the amp being purchased on Ebay, the BestBuy service gauruntees ARE transferrable as long as the item hasn't already been replaced. The seller provided the documentation and original receipt. Assuming, it has not already been exchanged once, then they will attempt to repair or replace it. Then the question will be whether or not they are willing to give me a comparable amp performance wise, or just cost wise. If its based on sales price (which it probably is), then the Fosgate 700S is going back to seller or I'll have to take it up with Paypal, or worst case, I'm screwed :(
3) The Fosgate700S is running bridged with a 4 ohm load from a single PowerAcoustik 12" dual-2ohm (wired in series) 700wRMS sub. The amp is rated at 700wRMS (bridged) @ 4 ohms. As for the input voltage, I'm not really sure, however, there are no voltage indicators on the gain dials on the Fosgate amp, so it will have to be tuned by ear. . . . . as a note, my last amp, the Kenwood was also running bridged w/ a 4 ohm load.
Thanks for starting the process. . .I might add I'm pretty sure I mentioned this all in the original post, but as it was long, some gets lost in that ;)
eldevioso on 12/30/2004 15:27:20
Here's a link to the sub:
http://www.bestbuy.com/site/olspage.jsp?id=1051384109574&skuId=5344246&productCategoryId=cat03081&type=product
Victor on 12/30/2004 15:59:23
OK..., that sub is a 700wrms sub..
anyways now lets get to the original problem..
1:- fuse near the battery cud have blown .
2:- the amp fuse cud have blown.
3:- improper grounding.
4:- extreme low loads which the amp cannot take.
5:- damage to internal parts of the amp.
All these cud be the reasons for the problem you are facing.
step one. remove the connection of the sub to the amp.
replace the blown fuses if any.
turn on the amp and let it be turned on for quite a while when the car is running as well as when it is stationary. . see if it shuts down itself without any active load on it.
see how much heat it generates without working and does it smell bad still..?? any fumes or smoke??
if this is the situation and you still see problems then there is definitely something wrong with the internal parts of the amp..and you need to win a battle to get it replaced by any e-tailer.
if there is no problem then.. it is thus derived that the amp stops performing when subjected to a specific load ( ie. your sub )
now to check that ..
two things can be wrong here.
wiring and gain settings.
regarding the gain settings .. both the left as well as the right channels shud have similar gain settings..
since both the channels have seperate gain settings it means that the amp uses 2 amplification circuitry to amplify the right and the left channels individually.. there cud be problems here if the gain settings are different on both the channels..
try setting the gain settings at a value at which you HU's output is rated. ( RCA voltage ).
values lower or higher thatn that can either harm you amp speakers or HU in some way.
now the next step..Wiring...
at first check the way you have wired the voice coils of your sub ( may be you have wired them to 1 ohm ie. in paralle rather than 4ohms ie.series .. it is possible that you were lucky to have the kenwood amp survive at 1ohm and u wud have never noticed the big blunder..trust me even i have done that a few years back when i was a child in car audio )
now if the wiring of the voice coils of the sub is right then we now have to check they way we have wired the sub to the amp..
have you wired each voice coil individually to each channel or bridged them and wired the sub to the... {+ve} of 1 ch and {-ve} of the 2nd ch..?
try going thru all over it ( wiring ) again..
if it works out you sure have gone wrong somewhere in the installation.. if it doesnot .. the only option would be replacing the product..
Let us know before you buy the replacement.. so that we cud help you select an appropriate product for the application.
Victor...
Ps:- digital monobloc amps are much more efficient and reliable for subwoofer applications.. plan on buying one if you got the worst luck and dont get a refund or replacement..
Victor on 12/30/2004 16:03:40
here is a .pdf file from Power acoustik..
it shows the way the sub should be wired for different kinds of load..
look at the way they have wired it for a 4 ohm load and cross check it with the way you have done it.. i suspect wiring as the only big problem besides internal damage..
Victor..
Victor on 12/30/2004 16:05:48
hehe.... i forgot to paste the link... i do this a lot..lol..
ok .. here it is..
http://poweracoustik.com/SUPPORT/MANUALS/PA-FUBRWoofer.pdf
Victor...
Victor on 12/30/2004 16:10:14
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&category=39737&item=5740713518&rd=1
is this the seller you got it from???
Victor...
eldevioso on 12/30/2004 17:54:59
Thanks for the links. And no that's not the seller. I bought from an individual not an e-tailer. However, he is being cooperative thus far on the situation. As for the issues:
1) I wired the voice coils in series, by jumping the positive from coil 1 to negative of coil 2. Then I ran a wire from the available remaining positive and negatives to the wiring block on my box. The diagram in the .pdf supports this. However, I will check the load again with a multimeter to make sure that this is the case, and if not I'll fix that. In regard to the speaker, its worth noting that the box is built to spec within 0.02 cu feet I would say, including port #, size, and length (just in case that helps).
2) I will definitely try the "no-load" testing method. Hopefully sometime tonight or tomorrow as I have the day off.
3) As for the list of possibilities, the fuse near the battery DID blow. That's why it shut off. However, I'll need to try the no-load test to see if there is some problem internaly (which I suspect there is). Further, there is no fuse built into the amplifier (unless I overlooked it - and I'll double check). The ground is good, as it was working before and hasn't been altered, and is securely fastened to the new amp. I'm confident the load wasn't an issue, but like I said, I'll double check to be sure.
So, that leaves us with either a fluke short in the fuse by the battery or internal amp problems. In this regard, would the fact I was using a 40 fuse instead of the recommended 60 fuse come into play?
4) As for matching the gain to the HU, I could use some help here. It is my understanding that you can use a multimeter to read the input from the HU from the RCA's. Yet, since the Fosgate doesn't have markings on the gain dials (ie...there is nothing to say what voltage you're setting it to, it simply has an arrow pointing in the direction) how can I determine what voltage the amp is set at so that it matches the HU. Can I measure somewhere, like the speaker output?
..and as a final note, the speaker is wired in bridge mode as you described. With the voice coils in series (to be double checked ;) I'll let you know what I discover and we can go from there.
Victor on 12/30/2004 19:14:20
wow.... those links made this post a very lenghty one...hehe.. i mean in actual page width....hahahaha
hey if you are around.. why dont u join in the chat room.. its much easier to deal with such problems in there..
Victor..
admin on 12/30/2004 20:31:17
Ok.. after checking everything let us know the details of how you checked and what results did u derive..
regarding the fuse in amp.. all the amps.. have a fuse.. it is the basic saftey measurement for all the car audio amps.. so the possibility of a fuse not being there is not even 1 in 10000.. but the RF amp models after 1993 stopped providing user servicable parts.. and have incorporated the fuse on the main board itself..
read this page..
http://rockfordfosgate.com/scripts/rightnow.cfg/php.
exe/enduser/std_adp.php?p_sid=Z_Nonjuh&p_lva=&p_faqid=41&p_created=
948148912&p_sp=cF9ncmlkc29ydD0mcF9yb3dfY
250PTE2
JnBfc2VhcmNoX3RleHQ9Um9ja2ZvcmQgRm9zZ2
F0ZSA3MDBTJnBfc2VhcmNoX3R5cGU9MyZwX3
Byb2RfbHZsMT05JnBfcHJvZF9sdmwyPX5hbnl_Jn
BfY2F0X2x2bDE9MSZwX3NvcnRfYnk9ZGZsdCZw
X3BhZ2U9MQ**&p_li=
replace all the blown fuse before you go ahead.
read the following links too..
http://rockfordfosgate.com/scripts/rightnow.cfg/php.exe/
enduser/std_adp.php?p_sid=Z_Nonjuh&p_lva=&p_faqid=43&p_created=
948817670&p_sp=cF9ncmlkc29ydD0mcF9yb3dfY
250PTE2JnBfc2VhcmNoX3RleHQ9Um9ja2Zvcm
QgRm9zZ2F0ZSA3MDBTJnBfc2VhcmNoX3R5c
GU9MyZwX3Byb2RfbHZsMT05JnBfcHJvZF9sdmwy
PX5hbnl_JnBfY2F0X2x2bDE9MSZwX3NvcnRfYnk
9ZGZsdCZwX3BhZ2U9MQ**&p_li=
http://rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser
/std_adp.php?p_faqid=46&p_created=950313207
dont forget to read the above links in detail.. shud prove very useful.
Victor..
danielm87 on 12/30/2004 21:05:01
I have personally been in a similair situation that this guy has been in. I replaced my old amp and subs with bigger ones, and quite unfortunately, and unitelligently, was using a 20A fuse on the power cable, running 600 watts to two subs. Needless to say, whenever the HU's volume level went to the halfmark point, that 20A fuse blew.
I assume not too many people have adressed this situation, but i beleive that you should ALWAYS have a perfectly appropriate fuse for the current draw your amp is taking from your car's charging system. Victor and everyone else have given you proper instruction, but MAKE SURE you get a 60A fuse (or better) on that power cable going to your amp, and pray to God that your amp is running okay internally.
You would do well to catch Swez or Vic in the chat room, it really speeds things up if you have a problem and need an answer quick.
I hope you work all your problems out with this situation and have a Happy New Year!
~Daniel Myers
swez on 12/30/2004 21:07:32
Hummmm, that burning smell troubles me too... What gage wire are you presently using here for the main power line? (hope you say #4 gage here) Good to see you back at CK!
After you replace the BAT fuse, if the amp works and all is well, you can check the voltage out from amp to sub with an AC volt meter. Using Ohm's Law, use sq. root of (Watts x Ohms) to determine volts output from amp to sub. I would anticipate close to 50 volts of signal from the amp at 700 watts into a 4 ohm load. That's about 13A of current as well. Use a #12 gage speaker wire from amp to box to sub min.
Your actual voltage readings may vary as most meters read RMS volts and the load (sub impedance) will vary with frequency. A sub wired at 4 ohms (nominal) will read about 3. 4 ohms off a DC ohmeter. However, when in action the impedance can go substantially higher than 4 ohms near Fs of the sub.
In all, I hope the new RF amp is OK and all you have to do is readjust the gains a tad. Double check your wiring for melting or scorch marks. Hopefully, the main power wire did not short to ground, hense blowing that 40A fuse. This RF amp can pull some serious current as it is a Class A/B amp. (700/13.5 = ~52A RMS... almost 90A peak draw)
Good luck and let us know what you find out OK?
Swez
eldevioso on 01/2/2005 17:03:07
Glad you remembered me Swez. It has been awhile but this is definitely the first place I turn to when I have a problem.
As for the power wire from battery to amplifier, I wanna say its 8 gauge, yet this is definitely the maximum size the RF amp can accept as I could barely get the wire inside the connector terminal. Also, I'm pretty sure the power wire didn't ground out, as it wasn't moved at all from teh old installation (ie. no tugging, no pulling no nothing). However, I will check it when the whether clears, as I don't have an appropriate work facility when its raining ;)
As for the draw of the amp, it was substantially higher than the Kenwood as I noticed the lights were dimming while the car was running which never happened with the older amplifier. That's antecdotal, but I know its pulling hard from teh electrical system.
So here are some new questions:
1) Given that you say it draws roughly 50A and peaks at 90A, is there a benefit to having a very large fuse up front, or would it be safer to keep it at 60A?
2) Thanks for the writeup on the voltage measurement. However, I would like to figure out how to properly set the gain. I mean, I can measure the signal coming from deck, but hte RF has no markings on the dial. Since I don't have advanced equipment, am I reduced to using the "ear" method to set them?
3) In regard to the gain settings, I had them at only 25% from teh left. Is it possible that I should have to back them all the way down to the left? If so, what signal voltage measurement should I expect to find requiring the gains to be set all the way down?
Thanks in advance. And an update before Ive had a chance to tinker with it, is that Best Buy still services this amp, and said that they will rebuild it for me, assuming something melted internally (which must be the case as teh smell didn't go away for 3 days). So I will have all new internals, which will be nice :) I'll keep yall posted.
swez on 01/2/2005 22:19:41
A #8 wire kit is really pushing it if you have 60A+ pulling from the amp. That burning smell, may be the amp, or it could be the power line insulation heating up???
Gain settings are to match up with HU output voltage. If you have a min of 250mV (1/4 volt) and max of 4.0 volts, the HU output should match close to amp gain settings. Harder to do by ear, but if your gains are set too low (say 2.0 volts) and the HU puts out 4.0 volts, amp reaches max power at ~2.0 volts and lower input setting clips amp badly.
Better to get out the tech manual for that amp and determine the proper gain settings from HU with an AC voltmeter at amp inputs. (10Kohm load resistor)
What is the full part # of that amp?
Swez
CSR on 01/3/2005 11:50:52
I dealt with something very simular to this story, just last weekend. A freind of a neighbor did the same thing. He had a 200 to 300 watt amp pushing a 12" sub and replaced the amp with a 700 watt unit. Same story, same results. The 8 gauge wire he had for the old amp couldn't power the new amp and fried it. He got that replaced and we installed it with a new power line and fuse. I asked if the sub was rated for that much power and he said it could handle twice that. After he got home he gave me a call and said he blow his sub. Next weekend, we'll install a new box with better speaker wires. Sometimes you just need to check things out yourself. After a few phone calls, I had him bring his car over so I could see what the problem was. 3 nights of phone calls vs. 40 sec of looking at the car to figure out what the problem was.
eldevioso on 01/3/2005 17:49:58
The full part number is: Rockford Fosgate "Punch 700S" and the .pdf file is here:
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/fattach_get.php?p_sid=FVNnaEuh&p_tbl=9&p_id=278&p_created=1083252061
but it says there in the .pdf that the terminals will "accomadate up to 8AWG." This makes sense as I couldn't possibly shove a fatter wire into the block.
However, would I benefit by running a fat 4 AWG cable back from the battery into a distribution block, with an 8AWG going from tehre to the amp. Ultimately this may be necessary as I want to hook up the old Kenwood to run my highs.
Unfortunately all the manual says about gain settings is that you can configure them will an oscilloscope. Well I don't have access to one. But I do understand teh gist of gain settings. That's why I had mine set "high" (from your description) or at the setting that makes the least power for the same input signal. I will measure the input signal for sure and relay that to yall. But, even then there are NO markings on the amp to tell me what voltage the gain dials are set at.
As for the burning smell, its definitely coming out of teh amp. I mean, its been a few days now with the amp off teh entire time and you can still smell the remnants from the vents of the amp. I will visually and olfactorily ;) inspect the wiring in addition though.
swez on 01/3/2005 23:43:38
If you are planning to add a 2nd amp soon, definitely upgrade to a #4 power line from BAT to a D-Block. From there, can use the #8 wire you have now, to power each amp.
Sounds like the "Magic Smoke" was let out of that RF amp. If it still works... good. If not, need a trip to the repair shop or swap it out for a new unit. But if you do swap it out, definitely use a Class D sub amp as they draw less current for the same wattage output.
You may get lucky and just peel off the cover plates and look inside the amp. Your eyes and olfactory sensors will tell where the problem lies. My guess, this amp pulls too much current and the problem happened at night? (lights & heater on?) If that was the case, voltage from the electricals may have dropped to a point where the amp lost voltage and wound up pulling excess current to meet output demand.
Swez
PS Gain settings may be a factor here too. Without accurate markings, are flying blind. When we don't know what gain settings to use, midpoint is usually a good place to start.
Victor on 01/4/2005 01:36:06
I feel Its ridiculous for a company like RF to not provide markings on the gain settings..
Victor..
uochronos on 01/4/2005 03:50:25
unfortunatly victor there are very few amps with accurate gain numbers even... my phoenix gold amp is the best one i have personaly used it has 4 markings on it and are relativly accurate most other amps i have used though only show the low and the max and one in between. even then though using your ear to set it without distortion is better then trusting the markings which usualy are off a bit.
Chronos
Victor on 01/4/2005 05:37:04
wow... its really surprising.. cause most of the brands i have sold.. Sony..Blau..Pioneer..many Alpine..some Polk some JVC some Kenwood all of them have gain settings all marked with appropriate voltage ratings at 4-5 stages..
( if you are pointing on their accuracy then i would agree with you that they may bot be as accurate as mentioned.. but as far as the marking is concerned i have seen them on most of the amps i have sold till now..)
Victor...
eldevioso on 01/5/2005 00:48:26
**UPDATE**
Well yesterday the rain let up and I was able to yank the amp outta the car. I took it to the BestBuy technician who bench tested it and said that it was Okay. Perplexed, I had him come out to the car and measure the ohms of the sub as it was wired. Too my shock it was showing 2 Ohms!!!
I couldn't understand how that could've happened. Since, the speaker is a dual, 2ohm voice coil setup, that didn't make sense. The tech, and his supervisor, rudely informed me that BestBuy has never carried a dual 2ohm voice coil sub and that I had unknowingly wired dual 4ohm coils in parallel. Well that did it for me and I knew they were full of crap. As you can see in the link from BestBuy's web page for my speaker, that I was correct about the coils and I had wired them in series.
Well, I went ahead and bought a 60 A fuse holder and fuse, and spliced it inline by the battery. I reconnected the amplifier, backing the gains all the way down. When I did this I realized that they were at 75%!!!!! from full clockwise. Unbelievable!!!! The arrow was pointing at 9 o'clock, and I turned it counter clockwise. It kept turning to 8, 7, 6, all the way to 2 O'CLOCK!!! So at full minimum on the gain, the damn thing is pointing to the right! Wow, everyone should take note that the left side of the dial doesn't necessarily mean its at its lowest setting.
So I backed the gains ALL the way down and disconnected the speaker from the amp. I ran the system for a few minutes and the fuse remained intact and the amp wasnt' smelling. Then I turned off stereo, and reconnected the speaker. I immediately found that the speaker was blown. Then it dawned on me, that one of the voice coils must've blown. That's why it was showing 2ohm rather than 4ohms, as it should in the configuration I wired it in.
Today I removed the sub from my tube, and checked the ohms of each coil. Sure enough, one of them was 1.8ohms, and the other had no reading. There was my answer. Furthermore, I noticed that the burning smell wasn't coming from the amp, although I was sure of it, it was coming from the speaker!! I also noticed the single 12AWG wire that I had bridged the coils with was smoked and smelled like crap. So I returned the sub and exchanged for a new one.
This time, I bought some new 12AWG cable and rebridged the new sub. Rewired the tube, and checked ohms. 4.2 ohms. This I took as a good sign. And reconnected it to the system. It played fine. I then slowly adjusted the gains from 2 o'clock to about 6 o'clock on the dial. I then adjusted deck bass controls and remote bass control (remote to about 66%) and it sounds good. It definitely doesn't hit as hard as it was before I blew the sub the last time, but I'm sure that has something to do with the gain settings having been 25-30% higher before.
Sadly, I noticed a little bit of the burning smell again, and this time the amp was warm, but the smell went away. I tried to measure the AC Voltage coming in on the RCAs with them disconnected from the amp, and the system on low volume, but the measurement was ranging from 1-10V. Unless I had the multimeter setting wrong (which I might), I don't know if I'm measuring this right. It seemed to peak as the song that was playing changed.
1) How do I check the signal voltage from the RCAs? What multimeter settings and should the stereo be on or off?
2) Would it be worth while to go and have a reputable shop tune my system...as I think I should be able to safely get a little more performance out of the amp.
3) Is it possible that one of the channels inside the amp isn't performing as well? It is running in bridged mode, but my thoughts are if one of tghe channels is toast or on the way out, then bridged performance would suffer as well.
....thanks for all the help guys.
Victor on 01/5/2005 02:20:52
This is what Rockford Fosgate has to say about Gain settings..
Question
How do I set the gain and bass control levels on my amplifier?
What are the right settings for the gain and bass controls on my amp?
Answer
Correctly setting the Gain controls on your amplifier is easy if you have some signal test discs and an oscilloscope! But, if you don't happen to have those available, then you may have to do some common-sense guesswork to "dial-in" your amplifier.
The Gain control is NOT a volume control! The gain adjustment (or control) is a level-matching control that adjusts the amplifier to work with the electronic piece(s) used before the amplifier. This piece before the amplifier could be the head unit, an EQ, or a crossover, and you set the gain control on the amplifier to match that unit's pre-amp voltage level. You can find out the unit's preamp output level in the owner's manual for that unit, as most manufacturers know you need this information in order to set up your system.
Essentially, by dialing-in the gain control, you're telling the amp how much signal you're putting into it so the amplifier will reproduce the signal accurately. If you have the gain set too high, the amp will make full power right away, and you'll have problems with distortion and "clipping". If the gain is set too low, the amp may still make full power, but it might not sound as loud as it should, and you'll think you aren't getting much volume. Our amplifiers are capable of accepting a signal input level from 250 millivolts to 4Volts, and you change the sensitivity by adjusting the gain control clockwise (more sensitive for low-power decks like 1-Volt units) or counter-clockwise (less sensitive for high-powered decks like 4-Volt units).
Since we do not put "indicators" or markings on the side of the amp to indicate gain levels for specific input voltages, this is where you will have to do a little "educated guessing" to set the controls up correctly. An oscilloscope's signal-measuring capabilities would come in handy right about now, as you could read the output levels of the amplifier while playing test tones (like a 1KHz tone) to determine at what point your amplifier "clips", and that's where you stop turning up the gain control.
But, if you don't have any of this cool stuff, then you'll have to assume the gain control is like a progressive-gain dial that becomes more sensitive as you turn it up (clockwise). We usually tell people that if they have a 4-Volt head unit, turn the gain all the way down (counter-clockwise); if they have a 2-Volt head unit, turn the gain 1/3 of the way up (clockwise); if they have a 1-Volt head unit, turn the gain 2/3 of the way up; and for 500mV decks, turn the gain 3/4 of the way up. While these suggestions are buy no means 100% accurate, they will work fine most of the time. When in doubt, have a professional double-check your work.
As far as the Punch Bass control goes, setting it correctly is a matter of both personal preference and the type of enclosure you are using for your speakers. If you are using your amplifier with a speaker (or set of speakers) that are loaded into sealed enclosures, then generally we recommend setting your amplifier's Bass control no higher than 1/4 of the way up. If you are using a ported enclosure for your speaker(s), then we generally recommend setting the Bass control no higher then 3/4 of the way up. Because the Punch Bass control is really an equalizer, you should not use it if you already have an EQ hooked up to your system (unless your EQ does not cover frequencies below about 70Hz).
If you're unsure of the best way to set up the gains or bass controls on your amplifier, we recommend you seek the assistance and advice of your local Rockford Fosgate dealer. They have the knowledge and equipment necessary to be able to set your gear up right!
Victor...
Victor on 01/5/2005 02:37:15
This explanation has really Pi$$ed me off..
The worst effort I have seen by a reputed company to back their stupid acts..
a whole bunch of $hitty ways to set up the gain settings and bass control....
" educated guessing" hahahahahahahaha....lol.. as if guys who use the RF amps are a bunch of uneducated guys...
hehehehe...so if you dont want your amp to clip and distort u gotta buy an oscilloscope and testtone disks... or do " educated guessing"...lol..
and then they write something like this..
"While these suggestions are buy no means 100% accurate, they will work fine most of the time. When in doubt, have a professional double-check your work"
and
"If you're unsure of the best way to set up the gains or bass controls on your amplifier, we recommend you seek the assistance and advice of your local Rockford Fosgate dealer. They have the knowledge and equipment necessary to be able to set your gear up right!"
a nice way to make the RF dealers earn more just from doing minor tweaking like this... leave aside the price for installation..
so if one buys an RF amp he spends more time and money in setting it up right than the amount he spend in actually buying it..haha
Its disgusting..
Victor...
eldevioso on 01/5/2005 03:05:11
Yeah, i hear you on that. I've read that link three times now. It's pretty much worthless, as I'm still unsure if I've done it right. Although I did what they say. it really sucks, but hopefully teh experts here have a better solution for me. If not, I'll got the local shop that has helped me a lot with verbal troubleshooting. I'm sure they wouldn't charge me much at all.
swez on 01/5/2005 12:07:43
Hummm, I can see the frustration mountion in Victor... take a chill pill dude! Please edit your *&@#!!. TY
The RF explanation leave a lot to be desired for sure. But, the general idea is to match the HU voltage rating (70-80% max power) to the amp input stage. Most amps have a 10,000 ohm imput impedance. To get an accurate HU voltage reading, we need a patch cord with a 10Kohm load. The voltage is read off the terminal ends of the resistor. (AC volts)
Have a look: http://www.bcae1.com/gaincon2.htm
Really, it's not as hard to do by ear as one might think. But we have to train our ears to detect distortions and clipping. This is very difficult to do at high SPL levels. (above +90dB) Why? Because our ears get saturated with high SPL audio and begin to go into a "self-protect" mode triggered in the brain.
Note: Ever been to a loud concert and came out feeling drunk and disoriented? (but did not drink or "smoke" before the concert) Ringing in the ears are also common if we get too close to main speakers as well. The brain has determined our ears are getting too much input and
shuts that part of the brain down.
Finally, when we are tweaking for max clean SQL, we open the doors and step back from the vehicle and listen from a distance. It will still be loud inside the car, but as we walk about th rear of the vehicle at 10 feet or so, we can get a pretty clear indication of clipping VS clean audio signals.
Hope that helps,
Swez
eldevioso on 01/5/2005 13:59:43
Lets hear some more detail on the patch cord Swez...
uochronos on 01/5/2005 18:16:00
just a note here to have a shop set your gain for you usualy costs like maybe 20$ i think the local place i sent a buddy to when he asked for a good place to set up his amps only chared him 20$ and they set his gains and LPF and setting on HU for him and it came out sounding great. took the guy all of like 20minutes or so from what my friend said.
so RF saying to have a profesional do it is a good idea. infact i think my phoenix gold amps warranty is contengent on the amp being installed and set by a authorized dealer. and i knwo many other companies are like that althuogh they dont seem to uphold that rule often.
Chronos
swez on 01/5/2005 22:32:53
PATCH CORD:
An RCA connector on one end, with a 10Kohm resistor between the ground and center lead. We take our voltage readings off both ends of the load resistor.
Gnd.........X.wwww.X..........Center lead off HU.
X = probe locations
Swez
eldevioso on 01/13/2005 12:29:33
Just to make absolutely certain I have this right.
I purchased:
(1) Female/Female RCA jack.
(1 pack) 10K Ohm Resistors
(1) Spare RCA Cable
Here's what I think I'm supposed to do:
1. Plug F/F adapter into one of the signal RCAs coming into my amp.
2. Cut Spare RCA cable and plug male connector into the 'empty' end of the F/F adapter.
3. Attach one end of the 10K Resistor to the positive signal on the 'SPARE' RCA cable that I cut and connected.
4. Attach other end of the 10K Resistor to:
....a. The ground lead of the same "SPARE" RCA cable?
....b. Another ground on the chassis of the car?
5. Then measure from each end of the resistor?
Here's how I envision it:
HU-------o- (F/F Adapter) -o--(spare RCA 'cut')---X---ccc10Kccc---X--Ground
X= probe locations
ger_10 on 01/13/2005 13:53:21
is ther any one who could help me on my topic iam desperate for help..reply at wiring for car please
eldevioso on 01/13/2005 19:09:18
Jeez!!!
Please don't hijack my thread. Simply wait for a response, as people WILL get to your question with 24 hours without a doubt. Or go to the Chat and see if you can find an instant response. Don't post in other's threads, unless its ON topic.
Thanks.
Victor on 01/13/2005 19:48:04
cool down guys.. well wldevioso.. things like this happen.. its all due to frustration of not getting a response and also because he has problems with his system.. such frustration has crept in all of us during our early days in car audio.. take a chill pill..
As for you ger_10 how would u expect a quick response from anyone when you have not given complete details of your HU.. model number.. the wires on it and the wires in your car harness.. And anyways UK has already given you a very list of what colour wire goes where..
U are simply amazing UK.. never expected anyone to remember car specific colour coding.. thata a very nice explanation u gave him there.. keep it up..
Victor..
UKinstaller on 01/13/2005 19:53:51
that's pretty much my specialty at my work is hardwiring radios. i work in an area where many stereos are stolen and the goofy thieves cut the harnesses instead of unplugging them. seems to me like it'd be easier to unplug!! thanks though.
-UK
swez on 01/14/2005 06:11:32
Hummm, little squabbling here eh? Children... behave! LOL
Elde,
You have proper patch cords and hardware now. The hookup scheme is as you have noted and the grounding point to test, is the ground side of the RCA cable. That is your reference ground source. Your test fixture will look like this:
1. HU=======(f/f jack)=====RCA wire to 10Kohm resistor.
2. RCA test kack======(Center lead)------*(10K resistor)*------to shielded (ground) wire on test jack. The (*) denotes probe locations.
Note: The RCA cable has 2 wires. One is a braided ground and the center wire is Pos signal connection. The 10K resistor will be installed as you noted above. I have tried to amplify that idea in my diagram.
Once you have all this hooked up, probe the resistor with an AC volt meter scaled at 1-10 VAC. Turn on the HU, dial it up and measure the voltage at either end of the 10K resistor. That will be your HU output voltage. Got a number.... match gains on amp to that voltage reading.
Would anticipate a HU RCA reading between 2-5 volts.
Finally, when adjusting gains on amp, imagine a clock face type thing here. Mid point is say 12:00 position and a good place to start adjustments. Depending on the amp, as you move toward the 9:00 position the amp/sub may get louder (it may get quieter). This is the sensitivity aspect of the gain controls.
Note: In this case, max sensitivity is 250mV (1/4 volt) Min sensitivity is 6 volts per RF manual.
Anyway, start at 12:00 position and move gains to 9:00 and then 3:00 positions. The power to the sub will change dramatically as you sweep from 3:00 to 12:00 to 9:00 positions. The proper setting will be loud, yet distortion free with your HU volume settings at 60-75% of max.
Make sure your HU tone controls are set to flat. (0 boost or cut). Use no bass boost on the amp at this time either. Once you have the amp dialed in to produce full yet clean bass, you can measure the AC voltage at the sub input terminals. It should read pretty close to ~53 Volts AC when amp is at 700 watts output power, to a 4 ohm load.
FYI: You may find the speaker voltage readings are slightly higher or lower than 53 VAC. This is normal as inductive impedance (dynamic resistance) of the coils will change with frequency. However, if you see a huge variation in voltage... something is a bit off.
Whew... this is a lot of blabbing huh. Dang, I hope it helps!
Swez ><>
eldevioso on 01/18/2005 20:44:35
Ok..I think I understand. So the RCA test jack cable will be plugged into the F/F Jack. then I will cut the cable and attach one end of 10K resistor to the center wire (+) and the other end of the 10K resistor, looped back onto the braided (-) shield that encompasses the center wire.
Is this correct?
If so, I'll try this sometime soon and let ya know the results. Thanks a lot.
MrBrownstone on 01/19/2005 01:02:02
Burning smell, previously used amp. Refurbished is likely if smell is from AMP
eldevioso on 01/21/2005 17:42:35
The burning smell turned out to be from the first two woofers I've tried in this setup now. I'm on the third, ( a kenwood 400w RMS 12) and it seems to be holding up surprisingly. I'm using that as a fillin until i can assure myself amp is OK and that gains are set properly.
swez on 01/21/2005 22:59:40
Maybe we are barking up the wrong tree here guys. Blown sub #2? Is this a ported enclosure? It would seem so. The PA subs are designed for high SPL and decent SQ. However, if the PTF (Port Tuning Freq) is high for this enclosure, you can fry a sub in short order with high SPL bass notes, below PTF. Why? At PTF (and below), the sub does not motivate very well. It cannot cool the coils adequately and as a result... fried coil(s)
Say more about that enclosure as I am beginning to think the amp is not the issue, nor the sub. It may just be the enclosure is tuned wrong for your PA sub.
Swez
eldevioso on 01/25/2005 15:09:06
Swez-
I feel you may be right about the enclosure. However, I still would like final confirmation on the construction of the input voltage testing rig we were discussing. This is vital for me to know for this and future installs.
As for the enclosure, we discussed this one evening in chat. We came to the conclusion that I needed a HP Subsonic filter at about 35 hz. However, for educational purposes, for the rest of our community lets reiterrate.
ENCLOSURE SPECS:
-Custom 'self built' tube design with woofer on one end of cylinder and port 'centered' on rear end of cylinder.
-Ported enclosure with single 4" diameter 10.25 or 10.5" long port placed directly behind woofer, centered on rear wall.
-Dimensions (recalled from memory): 26.25-26.5" long w/ 14" inner diameter. Calculates to 2.22 cu. ft. based on the displacement of a Cerwin Vega 124 12" Single Voice coil that it was built for. (Note: Vega was many years old and finally gave out after playing trouble free for a long period).
**Using this information and the speaker specs from the PA sub, Swez calculated the PortTuning Frequency (PTF) to be either 32 or 38 hz. if I remember correctly**
As a final note, I am currently running this speaker, as BestBuy was out of the PA subs when I went back for #3.
http://www.bestbuy.com/site/olspage.jsp?id=1072284520697&skuId=6255161&productCategoryId=cat03081&type=product
This is temporary and I do not want installation advice on this sub as the output is dirty and I am unhappy with it altogether. Please advise on the PA sub. ***HOWEVER*** this 200wRMS Kenwood sub, in a 2+ cu ft. ported enclosure although it was designed for a sealed 1 cu ft. enclosure has run fine with no problems, no matter HOW hard and HOW much distortion I send it, with the EXACT same setup as the PA sub. Kinda funny eh?
swez on 01/26/2005 19:16:50
Have taked to an "expert" (my brother ... Swez #2) about this one a bit more and came up with some interesting feedback.
Dale mentioned that a sub in a larger ported enclosure will "unload" below PTF. He confirmed what we already discussed in that area. However, he mentioned that when the sub "unloads" it has a tendancy to reach and exceed X-max a lot faster, below PTF. This creates undue stress on the mechanicals of a given sub and failure is usually a given under high SPL conditions. Most times, the failure is damage to motor mechanicals. Especially high excursion subs with large X-max numbers.
Chances are good, your 2 PA subs failed as a result of lead in wire (tinsel leads) being overly stretched and pulled the voice coil connections apart. An autopsy of the failed subs would no doubt confirm this. The result is the same... one coil set will fail and give no resistance reading in this type of failure.
Your new Kenwood sub probably has far less X-max travel and only 1 coil of 4 ohms. It probably does not like the larger enclosure very well as it is larger than recommended. But, if you keep the power to it under control, it may survive the X-max issues due to stiffer suspension componets... but at high continunous power, the coil may fry before the suspension and motor assy fails.
The best you can do to keep it working, is to go easy on the SPL output of this sub. It's only rated at 200 Wrms. Yes, if the sub motivating well, it will cool the coil better... but if a large amount of clipping or mechanical distortion is present... it too will fail in time.
In short, if/when you get a new PA sub, change the enclosure airspace and perhaps, move the SS filter to a higher number. Dale suggested that if you are tuning to say 36 Hz., a 3rd or 4th order filter (18-24dB/octave filtering) here, will perform much better than a 2nd order filter. (12 dB/octave slope) If you don't have anything better than a 2nd order SS filter, better to raise the frequency it begins to roll of at. (say 50 Hz., rather than 36 Hz.
Comments?
Swez
eldevioso on 01/26/2005 20:41:06
Alright! This is interesting stuff! Here's a question for ya though. If the PTF is say 36hz, that is the tone that the enclosure produces correct? Well...if I use a 50 hz ss filter won't that cut out the optimal frequency of the enclosure or am I seeing this wrong? guess it doesn't matter as my amp's LPF is set at about 60 anyway.
And swez...please take one last look at my final message about the Voltage tester...i really wanna make sure i do that right and have that for the future.
BTW Here are my plans that I'll update yall with:
1) Have amp bench tested by someone knowledgable.
2) If amp is OK, try to utilize the proper SS filter.
3) Test the incoming voltage from head for future reference.
swez on 01/27/2005 12:44:24
You got it.... a proper bench test will consist of:
1. a sign wave generator (test tones, "0" dB ref)
2. a 2 channel O-Scope (to measure and view incoming/outgoing) signals
3. a dummy load (non-inductive resistor)
4. AC voltmeter
Your RCA voltage test jig is correct as well. Most amps have a 10Kohm input impedance for a load. The 10K resistor emulates that load.
SS filter.... in most cases, if we have a target cutoff point at say 36 Hz., a -12dB filter set at 50-60 Hz., will be ~8-9dB down at 36 Hz. You will have some low end bass, but it will help protect the sub from too much power below PTF. The higher the order of the filter, the steeper the cutoff slope will be. With one of these filters, one can roll off the power below PTF very efficiently.
In Pro installs, we have learned to use 3rd or 4th order SS filters (18-24dB filtering) along with "anti-clipping limiters" (clamping circuits) that provide the ultimate in subwoofer protection. This way, the DJ has no ability to go beyond a preset limit on SPL (presets) from the system and will not blow out expensive drivers. We use limiters on all amps that feed Tweets, MB, Mids & Subs. These are expensive active filters, but in the long run, they save a lot of blown driver issues and fried amps.
Some DJ's are NOT the sharpest tools in the tool box. So, we have to "dummy proof" the system as much as possible. LOL
Swez
eldevioso on 10/20/2005 22:17:30
Well....I never did get to much extensive testing, but that damn Kenwood sub is still taking the beating....and I've come to enjoy its sound, just had to back the deck's bass setting down a little more than other speakers, but all in all its ok....
However, now i have some JL 12w3s...so I'll be happy about those, when yall respond to my latest post ;)
swez on 10/21/2005 09:50:39
Got a wiring plan for you on your main post.
Welcome back,
Swez
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