My truck has a fairly thick (10-12mils?) poly sheeting lining the inside of the door. I have some Dynamat to install around the speaker openings. Should I slit the plastic, attach the mat to the sheet metal surface, then tape the plastic sheeting back as well as possible.
Another question, since the Infinity comps Im going to use up front are 2 OHM's and the Rockford comps I'll be using in the rear are 4 OHM's, Will it matter at all to the RF 450.4 amp that they will all be powered from. Does it matter that the front channels are seeing a 2 OHM load while the rear's are seeing 4 OHMs.
Does anybody have any resistors that I can buy to rig up a 2 OHM load and a 4 OHM load to properly set my amp gains? The 40Hz tone was a bit distracting coming thru my sub when I tried it before. I had a hard time adjusting the knob properly even with ear plugs at the proper volumne. I was vibrating too much GRIN Can I get them at Radio Shack or some place like that if not?
Replies (10)
Victor on 03/5/2007 09:23:52
yes....slit the plastic, attach the mat to the sheet metal surface, then tape the plastic sheeting back as well as possible.
for the 2nd question... No... the RF amp should not have a trouble if it sees the front channel as 2 ohms and the rear as 4. all the channels aplification circuitry are independant of each other..
all you will need to do is some bit of tuning with the xovers and adjust the gain such that you avoid overpowering them as the RF amp would put out 2 times more power at 2 ohms then it does at 4 ohms..
you would not need any resistor to match a 4 ohm load , the rf amp will perform just fine with different loads..
Victor...
swez on 03/5/2007 11:21:35
If the sub is bothersome when dialing in your mid/highs, just pull the RCA's or amp fuses out of the sub amp and that will take the boom out of the process. Just make sure to tape them up, (RCA's) as you work so they don't accidentally short to metal. (That could damage your HU preamps)
Since the front and rear channels on your 4 channel RF amp are independent adjustments, don't be surprised if the front gains are way different than the rear settings. As Vic said, the 2 ohm load will almost double power to the front speakers as opposed to what the rears will be getting. No need for load resistors here. The gain adjustments should do the trick when blending for F/R stage balance points.
Tech Tip: In many vehicles, the rear speakers are often louder than the front. (3-5dB is common due to locations of the rear speakers) You will probably find that a 60% Front, 40% Rear ratio will blend pretty well. It's pretty much done by ear at low SPL levels, (a few watts)initially and then dial up the power to normal listening levels and adjust as needed. The remote will be a good tool to adjust HU volume levels and save some jumping around too.
If you can grab a helper, one does the amp gain adjustments while the other listens from the driver's seat. Use hand signals to communicate. The guy adjusting the gains may want ear plugs as they will be very close to the rear speakers. (That should be you Jimmy... not a rookie as you know this amp well and not slip, [short the outputs] with the adjustment tool)
Hope your Infinity's come in soon,
Swez
PS If you get the version with the M.M.D. tweeters, you may have to adjust the crossover attenuators to tone them down a tad. They tend to be a bit brighter than silks or cloth dome tweets.
jamesp on 03/5/2007 11:43:25
Thanks for the replies.
The reason I want the resistors is to use them for a load instead of the sub and speakers setting the gains with my volt meter to the proper voltage. When I used the 40 and 60Hz test tones w/ the sub hooked up it was brutal.lol There was only a tiny bit of difference in the pot setting for the correct voltage ...say it was 34 volts....turned it a fraction more and the voltage jumped to 40+ volts. I just want the sub amp gain set just right for a power match to my sub.
The Eclipse head unit is pretty cool. The memory stick will help with some things, however, I cant figure out how to write music files to it. It has to use Sony Atrac3 format. I downloaded the software but it doesnt work with Windows Media Player....anyone know how to do this....if not then no big deal...Im going to hook a microphone to the left aux channel and program the test mode where pink noise is generated and time alignment and other info is saved to the stick. Then you upload that info to Eclipses web site and it helps set up several parameters...when it is all said and done...Ill probably just push the button for the CSII feature. So far that sounds best to me....I just have to play around with it a little bit more..
The Infinities do have the MMD tweeters.
According to Fed Ex tracking my speakers are in Atlanta now and should be delivered tomorrow. Yea.
swez on 03/5/2007 12:54:14
Ohmite Mfging in Skokie, IL has load resistors that you can use.
Ohmite Mfg. Co.
1600 Golf Rd., Suite 850
Rolling Meadows, IL 60008
Tel: 1-866-9-OHMITE
(1-866-964-6483)
or 1-847-258-0300
Fax: 1-847-574-7522
info@ohmite.com
www.ohmite.com
I have 2 of 100 watt, 10 ohm resistors on hand. (5 ohms in parallel)
Part # is: L100J10R
To get a perfect 2 ohm load, you'll need 5 of these, (In parallel) and that's 500 watts power dissapation into a net 2 ohm load. Yes, if you air-cool them, they can dissapate more power as well.
The target voltage here, would be 31.6 volts = 500 watts @ 2 ohms. (As resistance goes up, target voltage will too, for the proper wattage range)
Care to give them a call and see if they have enough of that P/N on hand and can send them to you as engineering samples?
Swez
MrBrownstone on 03/5/2007 17:57:16
I don't understand why you would want to use resistors to change the load. The resistor would merely add heat...and not actually sound.
Furthermore, it would be stressing the amplifier, yet not providing more power. Adding an additional set of speakers would accomplish that load.
Think of the resistor as a toaster without a cooling system.
cybersailor420 on 03/5/2007 18:07:05
I believe he only wants to use them for initial gain-setting purposes.
jamesp on 03/5/2007 18:37:06
Ctbersailor, you are right on the money. I am wanting to do this: (linmk below) .My truck was vibrating a lot at 40Hz with the sub hooked up.
http://www.edesignaudio.com/edv2/gains_video.php
cplkittle on 03/5/2007 20:53:29
If you are going to use the load resistors to set the gain by voltage, First test the components. Single drivers will be slightly below standard impedence ratings. Crossovers will drop impedence as well. You may have 3.2 ohms instead of 4 ohms.
If you are going this far to make sure everything is set correctly, I would make sure everything is exact.
jamesp on 03/6/2007 08:35:20
I have aa Alpine 12" type R DVC 4 Ohm wired in parrallel for a 2 Ohm load I believe it tested at somewhere around 1.909 on my trusty ol Simpson VOM and slightly more on my DVOM.
I was under the impression that this is the way to do it correctly. When doing it "feel" there is a lot of difference in voltage near the optimum setting with very minute adjustment to the gain knob. For example at a setting reading 30 volts, just a tiny tweak to the gain knog jumped it to over 40 volts. I would have never known w/o the meter. But at those volumnes it was nerve racking.
swez on 03/6/2007 10:52:20
Speakers act like variable resistors, based on frequency. This is because they use a wire wound voice coil and this acts more like an inductor then an fixed resistor. When setting amp gains and using dummy load resistors, we can accurately set the power the speaker/woofer will get at a given frequency. Here's how a typical speaker works.
When we read voice coils with a typical meter, we are actually reading the DC resistance of the coil(s), not the true "impedence" of the coils. What does that mean?
The voice coils are actually variable inductors. They change ohmic values based on frequency (AC voltage) that is applied to the coil. If we were to run a sweep tone of sine wave AC from say 20 Hz to 20,000 Hz., and measured the voltage at the voice coil, we would see and hear changes in voltage/volume as the sweep progressed from low to higher frequencies.
Here's a numeric plot of how impedence/phasing changes with frequency for a Dayton 8" Quattro dirver:
http://www.partsexpress.com/pdf/295-545z.txt
Here's the gragh that is generated by that same set of numbers:
http://www.partsexpress.com/pdf/295-545.pdf
There are 2 plots on these pages. The upper plot are phase changes in signal as it goes through a sweep. The lower plot is impedence based on frequency. Note the change in resistance as frequency changes.
See the spike in inductive resistance at 36 Hz. (Fs = resonance of the woofer) This woofer is about 83 ohms at that frequency. At 100 Hz., this coil is now 5.14 ohms. This is where this woofer will be most efficient and have the highest output.
As we look at this 8" woofer response plot, the most effective frequency range of this speaker is between 60 - 250 Hz. (A very good midbass driver, but just a fair sub woofer) A ported enclosure would help this driver perform more efficiently below 55 Hz.
http://www.partsexpress.com/pdf/295-545s.pdf (SPL vs IMP plot)
Hope that helps,
Swez
Another question, since the Infinity comps Im going to use up front are 2 OHM's and the Rockford comps I'll be using in the rear are 4 OHM's, Will it matter at all to the RF 450.4 amp that they will all be powered from. Does it matter that the front channels are seeing a 2 OHM load while the rear's are seeing 4 OHMs.
Does anybody have any resistors that I can buy to rig up a 2 OHM load and a 4 OHM load to properly set my amp gains? The 40Hz tone was a bit distracting coming thru my sub when I tried it before. I had a hard time adjusting the knob properly even with ear plugs at the proper volumne. I was vibrating too much GRIN Can I get them at Radio Shack or some place like that if not?
Replies (10)
Victor on 03/5/2007 09:23:52
yes....slit the plastic, attach the mat to the sheet metal surface, then tape the plastic sheeting back as well as possible.
for the 2nd question... No... the RF amp should not have a trouble if it sees the front channel as 2 ohms and the rear as 4. all the channels aplification circuitry are independant of each other..
all you will need to do is some bit of tuning with the xovers and adjust the gain such that you avoid overpowering them as the RF amp would put out 2 times more power at 2 ohms then it does at 4 ohms..
you would not need any resistor to match a 4 ohm load , the rf amp will perform just fine with different loads..
Victor...
swez on 03/5/2007 11:21:35
If the sub is bothersome when dialing in your mid/highs, just pull the RCA's or amp fuses out of the sub amp and that will take the boom out of the process. Just make sure to tape them up, (RCA's) as you work so they don't accidentally short to metal. (That could damage your HU preamps)
Since the front and rear channels on your 4 channel RF amp are independent adjustments, don't be surprised if the front gains are way different than the rear settings. As Vic said, the 2 ohm load will almost double power to the front speakers as opposed to what the rears will be getting. No need for load resistors here. The gain adjustments should do the trick when blending for F/R stage balance points.
Tech Tip: In many vehicles, the rear speakers are often louder than the front. (3-5dB is common due to locations of the rear speakers) You will probably find that a 60% Front, 40% Rear ratio will blend pretty well. It's pretty much done by ear at low SPL levels, (a few watts)initially and then dial up the power to normal listening levels and adjust as needed. The remote will be a good tool to adjust HU volume levels and save some jumping around too.
If you can grab a helper, one does the amp gain adjustments while the other listens from the driver's seat. Use hand signals to communicate. The guy adjusting the gains may want ear plugs as they will be very close to the rear speakers. (That should be you Jimmy... not a rookie as you know this amp well and not slip, [short the outputs] with the adjustment tool)
Hope your Infinity's come in soon,
Swez
PS If you get the version with the M.M.D. tweeters, you may have to adjust the crossover attenuators to tone them down a tad. They tend to be a bit brighter than silks or cloth dome tweets.
jamesp on 03/5/2007 11:43:25
Thanks for the replies.
The reason I want the resistors is to use them for a load instead of the sub and speakers setting the gains with my volt meter to the proper voltage. When I used the 40 and 60Hz test tones w/ the sub hooked up it was brutal.lol There was only a tiny bit of difference in the pot setting for the correct voltage ...say it was 34 volts....turned it a fraction more and the voltage jumped to 40+ volts. I just want the sub amp gain set just right for a power match to my sub.
The Eclipse head unit is pretty cool. The memory stick will help with some things, however, I cant figure out how to write music files to it. It has to use Sony Atrac3 format. I downloaded the software but it doesnt work with Windows Media Player....anyone know how to do this....if not then no big deal...Im going to hook a microphone to the left aux channel and program the test mode where pink noise is generated and time alignment and other info is saved to the stick. Then you upload that info to Eclipses web site and it helps set up several parameters...when it is all said and done...Ill probably just push the button for the CSII feature. So far that sounds best to me....I just have to play around with it a little bit more..
The Infinities do have the MMD tweeters.
According to Fed Ex tracking my speakers are in Atlanta now and should be delivered tomorrow. Yea.
swez on 03/5/2007 12:54:14
Ohmite Mfging in Skokie, IL has load resistors that you can use.
Ohmite Mfg. Co.
1600 Golf Rd., Suite 850
Rolling Meadows, IL 60008
Tel: 1-866-9-OHMITE
(1-866-964-6483)
or 1-847-258-0300
Fax: 1-847-574-7522
info@ohmite.com
www.ohmite.com
I have 2 of 100 watt, 10 ohm resistors on hand. (5 ohms in parallel)
Part # is: L100J10R
To get a perfect 2 ohm load, you'll need 5 of these, (In parallel) and that's 500 watts power dissapation into a net 2 ohm load. Yes, if you air-cool them, they can dissapate more power as well.
The target voltage here, would be 31.6 volts = 500 watts @ 2 ohms. (As resistance goes up, target voltage will too, for the proper wattage range)
Care to give them a call and see if they have enough of that P/N on hand and can send them to you as engineering samples?
Swez
MrBrownstone on 03/5/2007 17:57:16
I don't understand why you would want to use resistors to change the load. The resistor would merely add heat...and not actually sound.
Furthermore, it would be stressing the amplifier, yet not providing more power. Adding an additional set of speakers would accomplish that load.
Think of the resistor as a toaster without a cooling system.
cybersailor420 on 03/5/2007 18:07:05
I believe he only wants to use them for initial gain-setting purposes.
jamesp on 03/5/2007 18:37:06
Ctbersailor, you are right on the money. I am wanting to do this: (linmk below) .My truck was vibrating a lot at 40Hz with the sub hooked up.
http://www.edesignaudio.com/edv2/gains_video.php
cplkittle on 03/5/2007 20:53:29
If you are going to use the load resistors to set the gain by voltage, First test the components. Single drivers will be slightly below standard impedence ratings. Crossovers will drop impedence as well. You may have 3.2 ohms instead of 4 ohms.
If you are going this far to make sure everything is set correctly, I would make sure everything is exact.
jamesp on 03/6/2007 08:35:20
I have aa Alpine 12" type R DVC 4 Ohm wired in parrallel for a 2 Ohm load I believe it tested at somewhere around 1.909 on my trusty ol Simpson VOM and slightly more on my DVOM.
I was under the impression that this is the way to do it correctly. When doing it "feel" there is a lot of difference in voltage near the optimum setting with very minute adjustment to the gain knob. For example at a setting reading 30 volts, just a tiny tweak to the gain knog jumped it to over 40 volts. I would have never known w/o the meter. But at those volumnes it was nerve racking.
swez on 03/6/2007 10:52:20
Speakers act like variable resistors, based on frequency. This is because they use a wire wound voice coil and this acts more like an inductor then an fixed resistor. When setting amp gains and using dummy load resistors, we can accurately set the power the speaker/woofer will get at a given frequency. Here's how a typical speaker works.
When we read voice coils with a typical meter, we are actually reading the DC resistance of the coil(s), not the true "impedence" of the coils. What does that mean?
The voice coils are actually variable inductors. They change ohmic values based on frequency (AC voltage) that is applied to the coil. If we were to run a sweep tone of sine wave AC from say 20 Hz to 20,000 Hz., and measured the voltage at the voice coil, we would see and hear changes in voltage/volume as the sweep progressed from low to higher frequencies.
Here's a numeric plot of how impedence/phasing changes with frequency for a Dayton 8" Quattro dirver:
http://www.partsexpress.com/pdf/295-545z.txt
Here's the gragh that is generated by that same set of numbers:
http://www.partsexpress.com/pdf/295-545.pdf
There are 2 plots on these pages. The upper plot are phase changes in signal as it goes through a sweep. The lower plot is impedence based on frequency. Note the change in resistance as frequency changes.
See the spike in inductive resistance at 36 Hz. (Fs = resonance of the woofer) This woofer is about 83 ohms at that frequency. At 100 Hz., this coil is now 5.14 ohms. This is where this woofer will be most efficient and have the highest output.
As we look at this 8" woofer response plot, the most effective frequency range of this speaker is between 60 - 250 Hz. (A very good midbass driver, but just a fair sub woofer) A ported enclosure would help this driver perform more efficiently below 55 Hz.
http://www.partsexpress.com/pdf/295-545s.pdf (SPL vs IMP plot)
Hope that helps,
Swez
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