I have a MB Quarts PL2800. If I wire my two 10" subs parallel, that takes it down to 1 ohm which that amp is not capable of (therefore I'll probably go series). Would the fuses on that amp protect the amp if the ohm load is too low or can damage be done despite the fact that fuses are in place?
Just not sure what the fuses on the amp protect it from. Thanks!
Replies (24)
ShootuhMcBustaCap on 10/16/2006 23:45:00
The fuses on the amp prevent it from pulling too much current. The number on the fuse tells you how much the maximum current pull on the amplifier, in amps. Amps are the measurement of current.
If running the ohmage too low causes the amp to pull too much current, than pop! we blow a fuse. So yes this can cause this, although it won't do it every time. And yes it can still damage the amp. I have blown 5 fuses this way, including one on the amp I'm running now, although I have still fried an amp after I popped the third fuse.....like baseball I guess. But it was a SONY, explains a lot.
When I blew my fuse in my old JBL amp, I had it running 2 channel bridged @1.33333 ohms (3 4Ohm voice coils) I didn't have the 25A fuse, so I replaced it with a 30A. Funny enough, it worked better than it did in the first place after putting the wrong fuse in. I do not reccommend this. I just got lucky.
According to google and aol searches, this amp does not exist. I have never heard of an MB amp not being stable at 1 Ohm. But I'm not an expert, try asking a gold on this one. They are way better on finding specs on stuff like this than I am.
Really want to be safe? Run a fuse rated 5A less in your amp CABLE than the one in the amp is rated at while in parrelel. If you keep popping it, put in the same amperage fuse. Be carefull and monotor the heat of your amp. If its getting way hot, way fast, goes into protect, pops a fuse or is making high levels of distortion at YOUR normal volume levels ( as in if you crank it all the time, crank it when you test, and give it some time to react {10-20mins}) run them in series. If there really Isn't a problem, leave them in parrellal.
In eitheir case, be responsible with the gain and bass boost. Set them at the minimum levels to meet your bass requirements. Whatever you do, just don't turn it up too high. If your gain control is marked with voltage ratings (usualy reads like 100mV-minimum, 5V- nominal, 1V- maximum), match it up with your head unit's output voltage as closeley as possible. Hope I helped.
Any more questions?
Tha Shootuh
swez on 10/17/2006 00:20:55
Fuses protect your wires from drawing more current than the wires can handle. They can also protect expensive speakers from excess power from a given amplifier. Lastly, they also protect the amp from drawing more current than the amp can safely handle.
We can calulate the appropriate fuse value based on wire gage it is attached to or protect a load from too much current draw. All that is needed, is the ohmic load of a device and the wattage it can handle. From there, we can determine what value fuse to use.
The fuses used in an amp, protect the amp from damage, if the load draws too much current for the amp to handle safely. Most good quality amps have protect circuits that monitor for shorted outputs, ultra low ohmic loads and excessive heat protection. These will shut the amp off if any one parameter goes outside the design parameters of the amp used.
Comments?
swez
jrwsound on 10/17/2006 00:42:47
Oh man do I feel dumb. This isn't an MB Quarts (I wish!) -- it's a MB Acoustics...http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000186841/mediaCode-ZX/appId-100000186841/Pr-p_CATENTRY_ID:100000186841
The only place I can find it is on JC Whitney -- no real specs to speak of. Can't even find a manufacture's website. I don't think this is a "good quality amp" with all the heat protection unfortunately.
Is the worst thing that can happen if I run it too hot on 1 ohm that I'll pop a fuse or is there further damage consideration? I guess my question is "Should I run the 2 subs parallel (risking the 1 ohm situation) or series to be on the safe side?"
Thank you both for your help.
MrBrownstone on 10/17/2006 00:51:17
Brands are created to appear similar to other famous brands.
MB Quart --MB Acoustic
Rockwood --Rockford
etc.
ShootuhMcBustaCap on 10/17/2006 01:11:08
If your using this amp in a 1 ohm bridged configuration, you could make pretty short work of it. Before I comment any further, can you send me some info on your subs?
jrwsound on 10/17/2006 01:36:50
Sure, also cheap -- 2 10" MTX Road Thunder subs in a dual bandpass box. I think these are the ones...
Road Thunder Subwoofer Specifications
Model RT10-04
Description 10" Subwoofer
Impedance 4 Ù
Frequency Response 35 - 150Hz
RMS Power (Watts) 200
Rec. RMS Amplifier 100 - 200
Power (Watts)
Voice Coil 1.5"
Magnet Weight (oz.) 30
Mounting Depth 4-5/8"
Cut Out Diameter 9-3/16"
Sealed Enclosure Net Volume .75ft3
Vented Enclosure Net Volume .8ft3
Port Dimensions 3" dia x 7-3/4"L
(Round Port)
Speaker Displacement .03ft3
swez on 10/17/2006 03:20:24
Do you know what fuses are used to protect this amp? With that, we can determine what kind of power and general performance you might expect.
Also, if it has not been used and you can return it, I would put that kind of cash into a quality amp that has a well known track record.
The MTX RT series is not a bad sub for low to moderate power amps. Not sure how well they will sound in a BP box of these dimensions. It depends on the port tuning side of the box.
Looks like the BP is tuned at 49 Hz. Good for making some loud bass in a narrow region of bass between 45-60 Hz. Good for max SPL in a narrow band of bass, but not very musical either. (Basically, a 2/3 octave wonder box)
This sub pair would do very well in sealed or a well tuned ported box. (If you are not happy with it as is)
swez
jrwsound on 10/17/2006 07:19:32
Thanks! I will post the fuses shortly. This is an amp that I got on ebay for a song -- no way would I have paid that JC price. But yeah, I hear ya for sure. I tested the amp for basic functionality and it seemed to work well.
jrwsound on 10/17/2006 08:22:56
Two 20A fuses on this amp.
swez on 10/17/2006 08:45:24
OK, that's about 50 watts RMS x 4 @ 4 ohms/channel and when bridged, about 150 x 2 @ 4 ohms per channel. Not a bad fit for those subs either. The safest way to use it for subs, is to bridge front channels for 1 sub, rear channels for other sub
It can also be used later as a decent 4 channel, full range amp if you so desire. Then, consider an efficient Class D amp for your subs as well. These subs can handle about 150-200 watts RMS each sealed and if you ported them for say 35 Hz, they can do a pretty good job on bass @ 300 - 400 watts RMS @ 2 ohms.
Have you tried the subs out yet in that BP box?
Comments?
Swez
jrwsound on 10/17/2006 13:27:56
Tried the subs out in the BP box just for functionality -- just to make sure they weren't blown or anything.
Actually this amp is only a 2-channel, not a four so the way you stated won't work.
swez on 10/17/2006 16:34:58
OK, thought it was a 4 channel for some goofy reason...still nets out to about 75 x 2 @ 4 ohms per channel or if bridged, you can expect about 300 watts RMS @ 4 ohms. This amp is not likely to be 1 ohm stable, even in 2 channel stereo mode.
Since your subs are 4 ohm SVC's, you can:
1. One sub per channel (stereo)
2. Bridge the amp and run both subs in series (8 ohms)
3. Use ONLY 1 sub and bridge the amp for extra power (~300 RMS)
Either way, same power to subs... ~75 watts RMS per sub. Fair at best and if you like the BP sound, this is one of the more efficient box designs to use.
If you elect to run only one sub, I'd suggest using sealed here, so the sub can handle the extra wattage. You'll have a spare sub too, just in case ya blow one up.
Swez
ShootuhMcBustaCap on 10/18/2006 13:29:41
A lot of amps can handle 2 ohm bridged, as long as you are carefull with amp settings and monitor heat buildup. I have never had a class D sub amp, but I frequently run two ohmmono setups. Here is how I get away with it.
Mount the amp so It gets wentilation on all sides
Don't turn the gain or head unit volume to excessive levels
Run oversized cables to everything, exept the remote wire. 'This helps the Amp "breathe'
Run the remote wire to a fuse or something as opposed to the head unit, in case the amp blows it doesn't try to take anything with it.
Follow the tricks in my first post too, just to be sure your safe. Blowing a 2dollar fuse in your amp cable while testing if your amp can handle the load.
I have ran a 2-channel amp with 3 4ohm speakers and an 8 ohm speaker. The brand was "Craig" and like yours, it was labeled as two ohm stable. It never overheated once in the year I used it, I still have it, and would still use it if the RCA inputs weren't damaged.
Personally, I would try bridging it first. This is a PERSONAL opinion, It has almos talways worked fine for me, with eception of a Sony 2 channel. But I will say, take my advice on this one at your own risk, as I hae blown One amp this way. Also that was when I was ignorant to turn gain and bass boost ALL the way up when I dialed things in, before I knew how bad that can be.
So check it out at your own risk, just be careful. Personally I would worry more about blowing your decent MTX's buy only giving them 75 RMS than frying a cheapie amp out of JC Whitney. Like Swez said, nomatter what, it wil probably sound fair at best. But at least if you run two Ohm mono, you can risk it and try to milk that ol' thang for every watt it's got. Thats what I do. Again, at your own risk
swez on 10/18/2006 14:30:55
When an amp states it is two ohm stable, it means they have tested it in two channel mode (2 ohms per channel) and it survived the testing process.
Now, if we bridge that amp, we MUST be mindful this amp is now stable at 4 ohms and above. Yes, there are many well built amps that will tolerate less than 4 ohms when bridged, but the amp is going to get hotter and work harder at such loads. That often shortens the life of such amplifiers as they have one main enemy.... HEAT!!!
FYI: Low ohmic loads, make the amp work harder and they also generate considerably more heat. This heating process is often controlled in better quality amps with thermal monitors. If the amp heats up to a pre-determined setpoint, the amp SHOULD shut off and cool down before it comes back to life again.
If the said amp cycles frequently between thermal shut off and back into low ohmic load operation, this sets up a tough situation for any power transistors to maintain. Sooner or later, the junctions will break down and the amp will die... period!
OK, as mentioned before, a single 4 ohm RT sub is 4 ohms. You can bridge this amp to 1 channel operation and power just 1 sub safely. The sub will handle extra RMS power, as long as it's a clean, low distortion signal and the sub cone is moving well enough to:
A. Cool the voice coil
B. Dissapates extra heat well
C. Is not subjected to excessive clipping
D. The enclosure is well matched to the sub and allows adequate air pressure to keep the sub from excess excursion
If these parameters are followed, that sub will take extra RMS power and probably sound very good and last a long time.
Keep this in mind when planning the next steps,
swez
jrwsound on 10/18/2006 14:37:10
Shoutuh -- I appreciate your tips, very helpful!
Swez -- For now I've chosen your option 2. "Bridge the amp and run both subs in series (8 ohms)" because I installed these for a kid who knows even less than I do and I won't be able to monitor the setup closely now that the install is done. He was very pleased with how it sounded. It was too loose and boomy for my taste.
Question on option 2: you said that it produces an 8 ohm load. I thought that since I am bridging the two channels that I then divide the ohms by two, making it 4 ohms. Is that wrong? Thanks for the clarification!
ShootuhMcBustaCap on 10/18/2006 16:23:40
No problem man! As for your question, bridging the channels does not affect the ohmage to the best of my knowledge. But just because I have never heaerd of it does not mean it does not occur.
Since you have chosen to run them at 8 ohms, make SURE that the gain is'nt turned up too high, as this will cause a lot of problems that usually end up blowing your sub. I have had it happen to me and it sucks, believe me. Also, makesure the same isn't occurring with the bass boost. I usually wnt run any kind of speaker unless I can give it at least 75% of the power it is rated at.
Swez can answer your question a little better I'm sure, as pretty much everything comes from my self taught expertise, Crutchfeild catologs,and Swez. He knows his stuff, he is the guy I go to with my questions.
By the way, what kind of music does your homie listen to? Bandpass is pretty awesome for rap, but even as a huge fan of BP, I will say they totally vacuumate for anything else. But as a rap fan, I can get away with it. But let's just say iturn my sub way down when I bust out the old Metal collection.
Glad I helped
Tha Shootuh
jrwsound on 10/18/2006 18:16:17
My "homie" digs on rap pretty much exclusively so that's why we sought out the BP. Thanks for the info on gain and bass boost. I may crank that down a bit tonight when I see him as I think I had it around 75% and crossed over around 90 or 100. If you are right about bridging the two channels not affecting ohmage then I may go back to the two ohm parallel option you have previously described and just monitor the amp more closely. I also need to consider Swez's one sub option further as well.
ShootuhMcBustaCap on 10/18/2006 20:29:16
Good choice then. That's why I selelected Bp for my ride. Double bandpass are reall cool in my opinion, beacuse the two subs spring off each other. Are the soundports on the face or the basket side of the subs? Nothing important, I'm just curious.
Yeah, 75% is pretty dangerous with underpowering like that. When runinng less than 75% of the power rating of the sub, like I am now, I wont turn gain past half. Does the amp have voltage markings on it? If it does, look up the specs of the head unit's output voltage and match them up, no matter how it sounds.
These markings represent the input voltage required for the amp to make its rated power. Not all amps have this, but in my opinion they should. Above that, provided the gain voltage is set lower than the head units output rating, most amps will be pushed into squarewave and clipping, which are the real killers of speakers, not just low power. For more on this, check out www.bcae1.com. This site has a ton of useful information.
By the way, 90-100hz may be a bit high for the crossover. At this point, vocals and midbass tend to enter the sub, which is not good.
for a litle tighter bass, set it form 60-80hz. This may be why the bass isn't quite to your liking. I run 50hz personally, but that is a pretty low crossover for most tastes. I probably wouldn't run it that low myself, but I have a really weak internal crossover. One of many reasons I'm going to get a Class D amp as soon as possible.
Swez's single sub operation may be the way to go. In the double bandpass, though, this may harm the other sub, or it mat have the effect of a passive radiator, this is one thing I have no Idea on.
I run only 1 bandpass 10" myself, actually most of my setups have been like this. People hardely believe I get that bass from that and a 400 watt peak amp. But most of my system's performance comes from my cables.
If I can give you one solid piece of advice, cables and connectors are build breakers. When I swapped out my entry level Tsunami RCA's for Monster Interlink 3's My bass literally doubled. The ones I was using were twice as good as the cheap Schosche peices of crap I was using before. Trust me, go for the good ones, spending $30 instead of $10 will make a big difference.
Amp to batt and amp to ground are important too. NEVER use less than a foot of ground unless absolutely neccessary. The shorter the ground, the more power it can make. I also run half the gauge size (the#, nopt the thickness) of cable on both connections. Remote wite is pretty cool no matter what you have, It's only for telling the amp to turn on.
Connectors, do you use them? A lot of DIYers don't, and some amps don't call for them, but some gold plated connectors will do wonders for conductivity and corrosion protection. Bare wire will oxidize rapidly and will eventually spread through the whole wire if left unabated, killing sound quality and causing distortion.
swez on 10/18/2006 22:25:29
If these are 4 ohm SVC subs, (1 voice coil/sub) wire the subs in series as the amp is not stable below 4 ohms when bridged.
If he had a decent Class D MONO amp, 2 ohms is perfect for that setup. But since this is a Class A/B amp, DO NOT RUN IT BELOW 4 OHMS... PERIOD!
Set the LPF at ~80 Hz. This will take out some of the bomminess and hopefully tighten up the bass a bit too.
Good luck,
swez
jrwsound on 10/19/2006 13:07:39
Sold! I will leave the wiring as it is (series). I have adjusted the LPF as well as brought the gain down just a bit.
I really appreciate all the adivce!
ShootuhMcBustaCap on 10/19/2006 14:13:25
No probelm man, were always glad to help!
swez on 10/19/2006 19:31:24
Care to help us too? See the link:
http://www.clubknowledge.com/cgi-bin/car_audio_faq/faq.cgi?g4639
Have a great day!
Swez
jrwsound on 10/22/2006 01:06:58
Done! Good luck on the fund raising drive and thanks again!
swez on 10/22/2006 09:59:13
Great and Thank You for doing your part here too. We appreciate your participation!
swez
Just not sure what the fuses on the amp protect it from. Thanks!
Replies (24)
ShootuhMcBustaCap on 10/16/2006 23:45:00
The fuses on the amp prevent it from pulling too much current. The number on the fuse tells you how much the maximum current pull on the amplifier, in amps. Amps are the measurement of current.
If running the ohmage too low causes the amp to pull too much current, than pop! we blow a fuse. So yes this can cause this, although it won't do it every time. And yes it can still damage the amp. I have blown 5 fuses this way, including one on the amp I'm running now, although I have still fried an amp after I popped the third fuse.....like baseball I guess. But it was a SONY, explains a lot.
When I blew my fuse in my old JBL amp, I had it running 2 channel bridged @1.33333 ohms (3 4Ohm voice coils) I didn't have the 25A fuse, so I replaced it with a 30A. Funny enough, it worked better than it did in the first place after putting the wrong fuse in. I do not reccommend this. I just got lucky.
According to google and aol searches, this amp does not exist. I have never heard of an MB amp not being stable at 1 Ohm. But I'm not an expert, try asking a gold on this one. They are way better on finding specs on stuff like this than I am.
Really want to be safe? Run a fuse rated 5A less in your amp CABLE than the one in the amp is rated at while in parrelel. If you keep popping it, put in the same amperage fuse. Be carefull and monotor the heat of your amp. If its getting way hot, way fast, goes into protect, pops a fuse or is making high levels of distortion at YOUR normal volume levels ( as in if you crank it all the time, crank it when you test, and give it some time to react {10-20mins}) run them in series. If there really Isn't a problem, leave them in parrellal.
In eitheir case, be responsible with the gain and bass boost. Set them at the minimum levels to meet your bass requirements. Whatever you do, just don't turn it up too high. If your gain control is marked with voltage ratings (usualy reads like 100mV-minimum, 5V- nominal, 1V- maximum), match it up with your head unit's output voltage as closeley as possible. Hope I helped.
Any more questions?
Tha Shootuh
swez on 10/17/2006 00:20:55
Fuses protect your wires from drawing more current than the wires can handle. They can also protect expensive speakers from excess power from a given amplifier. Lastly, they also protect the amp from drawing more current than the amp can safely handle.
We can calulate the appropriate fuse value based on wire gage it is attached to or protect a load from too much current draw. All that is needed, is the ohmic load of a device and the wattage it can handle. From there, we can determine what value fuse to use.
The fuses used in an amp, protect the amp from damage, if the load draws too much current for the amp to handle safely. Most good quality amps have protect circuits that monitor for shorted outputs, ultra low ohmic loads and excessive heat protection. These will shut the amp off if any one parameter goes outside the design parameters of the amp used.
Comments?
swez
jrwsound on 10/17/2006 00:42:47
Oh man do I feel dumb. This isn't an MB Quarts (I wish!) -- it's a MB Acoustics...http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000186841/mediaCode-ZX/appId-100000186841/Pr-p_CATENTRY_ID:100000186841
The only place I can find it is on JC Whitney -- no real specs to speak of. Can't even find a manufacture's website. I don't think this is a "good quality amp" with all the heat protection unfortunately.
Is the worst thing that can happen if I run it too hot on 1 ohm that I'll pop a fuse or is there further damage consideration? I guess my question is "Should I run the 2 subs parallel (risking the 1 ohm situation) or series to be on the safe side?"
Thank you both for your help.
MrBrownstone on 10/17/2006 00:51:17
Brands are created to appear similar to other famous brands.
MB Quart --MB Acoustic
Rockwood --Rockford
etc.
ShootuhMcBustaCap on 10/17/2006 01:11:08
If your using this amp in a 1 ohm bridged configuration, you could make pretty short work of it. Before I comment any further, can you send me some info on your subs?
jrwsound on 10/17/2006 01:36:50
Sure, also cheap -- 2 10" MTX Road Thunder subs in a dual bandpass box. I think these are the ones...
Road Thunder Subwoofer Specifications
Model RT10-04
Description 10" Subwoofer
Impedance 4 Ù
Frequency Response 35 - 150Hz
RMS Power (Watts) 200
Rec. RMS Amplifier 100 - 200
Power (Watts)
Voice Coil 1.5"
Magnet Weight (oz.) 30
Mounting Depth 4-5/8"
Cut Out Diameter 9-3/16"
Sealed Enclosure Net Volume .75ft3
Vented Enclosure Net Volume .8ft3
Port Dimensions 3" dia x 7-3/4"L
(Round Port)
Speaker Displacement .03ft3
swez on 10/17/2006 03:20:24
Do you know what fuses are used to protect this amp? With that, we can determine what kind of power and general performance you might expect.
Also, if it has not been used and you can return it, I would put that kind of cash into a quality amp that has a well known track record.
The MTX RT series is not a bad sub for low to moderate power amps. Not sure how well they will sound in a BP box of these dimensions. It depends on the port tuning side of the box.
Looks like the BP is tuned at 49 Hz. Good for making some loud bass in a narrow region of bass between 45-60 Hz. Good for max SPL in a narrow band of bass, but not very musical either. (Basically, a 2/3 octave wonder box)
This sub pair would do very well in sealed or a well tuned ported box. (If you are not happy with it as is)
swez
jrwsound on 10/17/2006 07:19:32
Thanks! I will post the fuses shortly. This is an amp that I got on ebay for a song -- no way would I have paid that JC price. But yeah, I hear ya for sure. I tested the amp for basic functionality and it seemed to work well.
jrwsound on 10/17/2006 08:22:56
Two 20A fuses on this amp.
swez on 10/17/2006 08:45:24
OK, that's about 50 watts RMS x 4 @ 4 ohms/channel and when bridged, about 150 x 2 @ 4 ohms per channel. Not a bad fit for those subs either. The safest way to use it for subs, is to bridge front channels for 1 sub, rear channels for other sub
It can also be used later as a decent 4 channel, full range amp if you so desire. Then, consider an efficient Class D amp for your subs as well. These subs can handle about 150-200 watts RMS each sealed and if you ported them for say 35 Hz, they can do a pretty good job on bass @ 300 - 400 watts RMS @ 2 ohms.
Have you tried the subs out yet in that BP box?
Comments?
Swez
jrwsound on 10/17/2006 13:27:56
Tried the subs out in the BP box just for functionality -- just to make sure they weren't blown or anything.
Actually this amp is only a 2-channel, not a four so the way you stated won't work.
swez on 10/17/2006 16:34:58
OK, thought it was a 4 channel for some goofy reason...still nets out to about 75 x 2 @ 4 ohms per channel or if bridged, you can expect about 300 watts RMS @ 4 ohms. This amp is not likely to be 1 ohm stable, even in 2 channel stereo mode.
Since your subs are 4 ohm SVC's, you can:
1. One sub per channel (stereo)
2. Bridge the amp and run both subs in series (8 ohms)
3. Use ONLY 1 sub and bridge the amp for extra power (~300 RMS)
Either way, same power to subs... ~75 watts RMS per sub. Fair at best and if you like the BP sound, this is one of the more efficient box designs to use.
If you elect to run only one sub, I'd suggest using sealed here, so the sub can handle the extra wattage. You'll have a spare sub too, just in case ya blow one up.
Swez
ShootuhMcBustaCap on 10/18/2006 13:29:41
A lot of amps can handle 2 ohm bridged, as long as you are carefull with amp settings and monitor heat buildup. I have never had a class D sub amp, but I frequently run two ohmmono setups. Here is how I get away with it.
Mount the amp so It gets wentilation on all sides
Don't turn the gain or head unit volume to excessive levels
Run oversized cables to everything, exept the remote wire. 'This helps the Amp "breathe'
Run the remote wire to a fuse or something as opposed to the head unit, in case the amp blows it doesn't try to take anything with it.
Follow the tricks in my first post too, just to be sure your safe. Blowing a 2dollar fuse in your amp cable while testing if your amp can handle the load.
I have ran a 2-channel amp with 3 4ohm speakers and an 8 ohm speaker. The brand was "Craig" and like yours, it was labeled as two ohm stable. It never overheated once in the year I used it, I still have it, and would still use it if the RCA inputs weren't damaged.
Personally, I would try bridging it first. This is a PERSONAL opinion, It has almos talways worked fine for me, with eception of a Sony 2 channel. But I will say, take my advice on this one at your own risk, as I hae blown One amp this way. Also that was when I was ignorant to turn gain and bass boost ALL the way up when I dialed things in, before I knew how bad that can be.
So check it out at your own risk, just be careful. Personally I would worry more about blowing your decent MTX's buy only giving them 75 RMS than frying a cheapie amp out of JC Whitney. Like Swez said, nomatter what, it wil probably sound fair at best. But at least if you run two Ohm mono, you can risk it and try to milk that ol' thang for every watt it's got. Thats what I do. Again, at your own risk
swez on 10/18/2006 14:30:55
When an amp states it is two ohm stable, it means they have tested it in two channel mode (2 ohms per channel) and it survived the testing process.
Now, if we bridge that amp, we MUST be mindful this amp is now stable at 4 ohms and above. Yes, there are many well built amps that will tolerate less than 4 ohms when bridged, but the amp is going to get hotter and work harder at such loads. That often shortens the life of such amplifiers as they have one main enemy.... HEAT!!!
FYI: Low ohmic loads, make the amp work harder and they also generate considerably more heat. This heating process is often controlled in better quality amps with thermal monitors. If the amp heats up to a pre-determined setpoint, the amp SHOULD shut off and cool down before it comes back to life again.
If the said amp cycles frequently between thermal shut off and back into low ohmic load operation, this sets up a tough situation for any power transistors to maintain. Sooner or later, the junctions will break down and the amp will die... period!
OK, as mentioned before, a single 4 ohm RT sub is 4 ohms. You can bridge this amp to 1 channel operation and power just 1 sub safely. The sub will handle extra RMS power, as long as it's a clean, low distortion signal and the sub cone is moving well enough to:
A. Cool the voice coil
B. Dissapates extra heat well
C. Is not subjected to excessive clipping
D. The enclosure is well matched to the sub and allows adequate air pressure to keep the sub from excess excursion
If these parameters are followed, that sub will take extra RMS power and probably sound very good and last a long time.
Keep this in mind when planning the next steps,
swez
jrwsound on 10/18/2006 14:37:10
Shoutuh -- I appreciate your tips, very helpful!
Swez -- For now I've chosen your option 2. "Bridge the amp and run both subs in series (8 ohms)" because I installed these for a kid who knows even less than I do and I won't be able to monitor the setup closely now that the install is done. He was very pleased with how it sounded. It was too loose and boomy for my taste.
Question on option 2: you said that it produces an 8 ohm load. I thought that since I am bridging the two channels that I then divide the ohms by two, making it 4 ohms. Is that wrong? Thanks for the clarification!
ShootuhMcBustaCap on 10/18/2006 16:23:40
No problem man! As for your question, bridging the channels does not affect the ohmage to the best of my knowledge. But just because I have never heaerd of it does not mean it does not occur.
Since you have chosen to run them at 8 ohms, make SURE that the gain is'nt turned up too high, as this will cause a lot of problems that usually end up blowing your sub. I have had it happen to me and it sucks, believe me. Also, makesure the same isn't occurring with the bass boost. I usually wnt run any kind of speaker unless I can give it at least 75% of the power it is rated at.
Swez can answer your question a little better I'm sure, as pretty much everything comes from my self taught expertise, Crutchfeild catologs,and Swez. He knows his stuff, he is the guy I go to with my questions.
By the way, what kind of music does your homie listen to? Bandpass is pretty awesome for rap, but even as a huge fan of BP, I will say they totally vacuumate for anything else. But as a rap fan, I can get away with it. But let's just say iturn my sub way down when I bust out the old Metal collection.
Glad I helped
Tha Shootuh
jrwsound on 10/18/2006 18:16:17
My "homie" digs on rap pretty much exclusively so that's why we sought out the BP. Thanks for the info on gain and bass boost. I may crank that down a bit tonight when I see him as I think I had it around 75% and crossed over around 90 or 100. If you are right about bridging the two channels not affecting ohmage then I may go back to the two ohm parallel option you have previously described and just monitor the amp more closely. I also need to consider Swez's one sub option further as well.
ShootuhMcBustaCap on 10/18/2006 20:29:16
Good choice then. That's why I selelected Bp for my ride. Double bandpass are reall cool in my opinion, beacuse the two subs spring off each other. Are the soundports on the face or the basket side of the subs? Nothing important, I'm just curious.
Yeah, 75% is pretty dangerous with underpowering like that. When runinng less than 75% of the power rating of the sub, like I am now, I wont turn gain past half. Does the amp have voltage markings on it? If it does, look up the specs of the head unit's output voltage and match them up, no matter how it sounds.
These markings represent the input voltage required for the amp to make its rated power. Not all amps have this, but in my opinion they should. Above that, provided the gain voltage is set lower than the head units output rating, most amps will be pushed into squarewave and clipping, which are the real killers of speakers, not just low power. For more on this, check out www.bcae1.com. This site has a ton of useful information.
By the way, 90-100hz may be a bit high for the crossover. At this point, vocals and midbass tend to enter the sub, which is not good.
for a litle tighter bass, set it form 60-80hz. This may be why the bass isn't quite to your liking. I run 50hz personally, but that is a pretty low crossover for most tastes. I probably wouldn't run it that low myself, but I have a really weak internal crossover. One of many reasons I'm going to get a Class D amp as soon as possible.
Swez's single sub operation may be the way to go. In the double bandpass, though, this may harm the other sub, or it mat have the effect of a passive radiator, this is one thing I have no Idea on.
I run only 1 bandpass 10" myself, actually most of my setups have been like this. People hardely believe I get that bass from that and a 400 watt peak amp. But most of my system's performance comes from my cables.
If I can give you one solid piece of advice, cables and connectors are build breakers. When I swapped out my entry level Tsunami RCA's for Monster Interlink 3's My bass literally doubled. The ones I was using were twice as good as the cheap Schosche peices of crap I was using before. Trust me, go for the good ones, spending $30 instead of $10 will make a big difference.
Amp to batt and amp to ground are important too. NEVER use less than a foot of ground unless absolutely neccessary. The shorter the ground, the more power it can make. I also run half the gauge size (the#, nopt the thickness) of cable on both connections. Remote wite is pretty cool no matter what you have, It's only for telling the amp to turn on.
Connectors, do you use them? A lot of DIYers don't, and some amps don't call for them, but some gold plated connectors will do wonders for conductivity and corrosion protection. Bare wire will oxidize rapidly and will eventually spread through the whole wire if left unabated, killing sound quality and causing distortion.
swez on 10/18/2006 22:25:29
If these are 4 ohm SVC subs, (1 voice coil/sub) wire the subs in series as the amp is not stable below 4 ohms when bridged.
If he had a decent Class D MONO amp, 2 ohms is perfect for that setup. But since this is a Class A/B amp, DO NOT RUN IT BELOW 4 OHMS... PERIOD!
Set the LPF at ~80 Hz. This will take out some of the bomminess and hopefully tighten up the bass a bit too.
Good luck,
swez
jrwsound on 10/19/2006 13:07:39
Sold! I will leave the wiring as it is (series). I have adjusted the LPF as well as brought the gain down just a bit.
I really appreciate all the adivce!
ShootuhMcBustaCap on 10/19/2006 14:13:25
No probelm man, were always glad to help!
swez on 10/19/2006 19:31:24
Care to help us too? See the link:
http://www.clubknowledge.com/cgi-bin/car_audio_faq/faq.cgi?g4639
Have a great day!
Swez
jrwsound on 10/22/2006 01:06:58
Done! Good luck on the fund raising drive and thanks again!
swez on 10/22/2006 09:59:13
Great and Thank You for doing your part here too. We appreciate your participation!
swez
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