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Discussion Starter #1
I'm getting mixed answers here.

I have a Kenwood KAC-8403 4/3/2 Channel Amp. I am running 2 speakers (4ohm each) in front (1 channel each) and bridging 2 channels for the sub, therefore I'll be running in 3 channel mode.

I've been told that I need an 8 ohm sub because I'm bridging 2 channels. I've also been told I need 4 ohm. Both by knowledgeable people. Which is it, so I can order the sub already!
 

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Brokedick Millionaire
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I'd go with the 8 ohm, that amp doesn't do much when bridged into a 4 ohm load.

rated at 60x4 into 4 ohms, or 90x4 into 2 ohms at a higher distortion rating, so its likely only 75 watts.

120 watts well dampened, or 150 watts so-so dampened.
 

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Brokedick Millionaire
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8 ohm for that amp, but 4 ohm will be fine, you plan on using that sub in a different system later, or upgrading to a better amp?

Then I'd get the 4 ohm. Think about the future, that way your not too limited.

That sub looks quite tasty in a slot loaded enclosure. Steep 24 dB/octave filter at about 30-32 Hz.......

Manville's company always has great products :)
 

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MAIN ONE IZ A CIVCSI
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8 ohm for that amp, but 4 ohm will be fine, you plan on using that sub in a different system later, or upgrading to a better amp?

Then I'd get the 4 ohm. Think about the future, that way your not too limited.

That sub looks quite tasty in a slot loaded enclosure. Steep 24 dB/octave filter at about 30-32 Hz.......

Manville's company always has great products :)
x2 i def. have to agree with this
 

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EG
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8 ohm for that amp, but 4 ohm will be fine, you plan on using that sub in a different system later, or upgrading to a better amp?

Then I'd get the 4 ohm. Think about the future, that way your not too limited.

That sub looks quite tasty in a slot loaded enclosure. Steep 24 dB/octave filter at about 30-32 Hz.......

Manville's company always has great products :)
From what I remember of car audio, I would agree with Bone. The amp will want an 8ohm, but a 4 ohm will be fine and be more adaptable for future stereo setups.
 

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Discussion Starter #10
I bought the 8 ohm. I want to optimize for this setup. That sub is relatively cheap, plus this setup is intended for this civic. I feel that a setup should be designed per car, not with intention of moving it around. I plan to use it about a year, because within I year my daily driver will be an S2000, and this civic will be turning into mostly/all track. However for now I need to maintain some sort of comfort level while I still daily drive it.
 

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Worst Mechanic Ever!
EG
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I bought the 8 ohm. I want to optimize for this setup. That sub is relatively cheap, plus this setup is intended for this civic. I feel that a setup should be designed per car, not with intention of moving it around. I plan to use it about a year, because within I year my daily driver will be an S2000, and this civic will be turning into mostly/all track. However for now I need to maintain some sort of comfort level while I still daily drive it.
I'm coming to your house and stealing your s2k. When you get it of course! :D

Sounds good. Some people like to keep their stereo options open. Personall, I agree that a systemshould be built according to the car and the person driving the car. I haven't had subs in my car for 2-3 years now and when I do replace them, it'll be with a single 10 instead of the 2 12's I had.
 

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4 ohm will be fine, you will get more power out of the amp.
Read over the specs of his amp (I did) before suggesting this comment.

A real amp, yes 4 ohm mono, his isn't up to the task.

Now, if he bridges the 4 channel amp to run the fronts and buys a good 2x100 amp which would shit out 350-400 watts into 4 ohm mono, then yes.

I think I'm the ONLY person who looked into his amps specs before suggesting anything.

http://www.kenwoodusa.com/Car_Entertainment/Amplifiers/KAC-8403

240 watt amp that MIGHT do 800 watts a on Taco Fart.

2 [email protected] 90 Watts × 4 (1kHz, .8%THD)
4 [email protected] 60 Watts × 4 (20-20kHz, .08%THD)
[email protected] 180 Watts × 2 (1kHz, .8%THD)
Maximum Output Power 800 Watts
RMS Power Output 60 Watts × 4 (1%THD+N) (4Ω)

Notice the RMS 60 w/ch/4 ohm rating is at 1% THD
 

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I'm getting mixed answers here.

I have a Kenwood KAC-8403 4/3/2 Channel Amp. I am running 2 speakers (4ohm each) in front (1 channel each) and bridging 2 channels for the sub, therefore I'll be running in 3 channel mode.

I've been told that I need an 8 ohm sub because I'm bridging 2 channels. I've also been told I need 4 ohm. Both by knowledgeable people. Which is it, so I can order the sub already!
Get the 4 ohm version and bridge 2 channels of your amp to get approx. 180w for the woofer. Use the remaining 2 channels to power your front speakers at 45-60w (4ohm) each. Remember to set the the gains on the amp accordingly matching your head unit output to prevent clipping.

This is a simple setup and works well. Although you will have 1%THD for your woofer when you bridge the 2 channel, but you wont be able to notice the 'noise' produced, especially at below 80hz. (most people cant hear the 'noise' produced at <1%THD).

When I use to compete at ISACA competition, I used to buy 4 channels amps and bridged them into 2 channel amps for my front speakers setup to save cost while achieving higher power output. No noise detection points were ever deducted from my score sheet.
 

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Will, you are correct, but that little amp doesn't have the dampening power for a good sub @ 4 ohm mono, likely why the spec was never listed.

A GOOD amp will almost double power at same THD rating when sent into half the ohms. Alot of it is the power supply. Since the new ratings are at 12.5v, the specs being listed at 14.4v are even more suspect.

Yeah, I gave up on IASCA when motorization and gauges took over the points, I'm SQL all the way.

This will be more than enough for most anyone.

 

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To those who are interested in amps selection.

http://www.tom-morrow-land.com/tests/ampchall/index.htm

I do agree with the article, however I still prefer amps from companies with better reputation due the build quality, better resale value and more accurate rating of power output,but not because of better "sound quality".

As long as u have adjust the gain to match the head unit output, u will not need to be afraid of distortion. (I used a oscillation scope to adjust the gain, however using the markings on the gain knob will suffice for most.)
 

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Transzex, yap. I agree with you. Nice Van GOGH. I still have my old PPI AM and M series amps when they use to underate their power. :)
 

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For those that are curious, JL said to buy 8ohm.
Most likely, they dont want u to put in more power than the woofer is rated at. If you have set the gain correctly, you shouldnt have any problems with 4ohm. besides with a 8ohm woofer, its only going to see half the power = weak.
 
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