fwillis0323

just installed a 8" sub in my '06. kept factory head unit and upgraded front doors and tweeters to new polk audio 6500 kit. i used the high level inputs for the first time ever. the sub sounds great and the fronts are unbelievable. my problems lie with road noise\alternator whine. i used the front center channel as my signal for the front doors, being as i never balance to the left or right, this works fine. i used the factory sub wiring for the signal of the new sub. power runs all the way to the battery with 2\0 cable, ground connects just under the trunk carpet with 4\0 cable. obviously signals are provided by the stock head unit, so i shouldnt have any power\rca feedback issues, yet i have horrific whine. i'm hoping to stay from LOC's if possible. does anyone have any advice? or suggestions? its been quite some time since i've done an install and there's a good chance i've missed\forgotten something.

Thanks for any help

pohljm

using the front center channel as the source for your front L&R components makes absolutely no sense. I think you would prefer your sound if it were playing in stereo!!. there isnt much material being fed to the center channel you prolly have the gains high to try and get some sound from the center channel and all your hearing is the aweful distortion from the OEM amp. your taking the signal after the OEM amp?

fwillis0323

I am taking the signal after the amp, tapped in right at the center speaker under the dash. Other than the sound being in stereo, the fronts sound perfectly fine as well as the sub. The gains on both the fronts and sub are actually only dialed in about half way, so I don't think i'm overclocking the amp. The gain on the head unit for the center channel is sitting at +3 which is where it always has been before ugrading anything, the bass gain is at -3, treble is at +4, and the sub is at +3. The road\alternator noise is unable to be heard while music is being played, although its still there it just can't be heard. I'm not getting distortion of the music, only a constant "interference" type noise. With the head unit on and turned completely down, the noise is unreal consisting of a slight "snow" sound accompanied with typical alternator whine. I actually pick up even more noise if the headlights are turned on. Obviously something is wrong somewhere, i'm just not sure where. Currently everything is disconnected waiting for a solution. I'm not sure if a LOC will help with the issue. Being as i've never used high level inputs before, i'm at a loss and considering switching to a LOC to see if it provides any relief.

pohljm

you should be taking the FL and FR signal pre amp and using a line driver if your amp needs the signal to be higher than the HU provides.

fwillis0323

I just picked up a LOC by aamp, heres the link. http://www.bestbuy.com/site/AAMP+OF+...&skuId=8014659.

Would this work? Or is the line driver my only option? If the LOC will work, does it get introduced before or after the oem amp?

I apologize if some of these questions seem uneducated. I haven't done an install since Kicker gold letters, Cerwin Vega strokers, Super Pros were main stream. So it's been several years. Thanks again for the help.

pohljm

I cant tell from the spec sheet on the site anything at all. the reviews are terrible. you certainly do not need rear channel outputs. If your going pre amp you need a device to increase the output voltage unless your amp can deal with the low output voltage from the HU. My JL amp works fine without anything. If your going after the OEM amp you will need a device to reduce the output to your amp.

For the life of me I have no idea why anyone would go after the OEM amp unless your just adding a sub tapped into the sub wires in the trunk. If your upgrading the entire system you want the cleanest source you can get and that is definitely not after the crappy noisy OEM amp. use front left and right from the HU and a line driver if needed by your amp.

fwillis0323

Fair enough. When you say use a line driver "if needed" how is it determined? obviously I dont have any other schematic type info for the amp other than whats provided in the box. The amp is a Polk PA660. I'm not certain how to determine if it would require a line driver. Luckily I can return the LOC and swap it for the line driver, so i'm good on that end, now I just need to find out if I even need the line driver. Thanks again.

pohljm

look at the owners manual. it looks like on that amp minimum input is 250mV. I would guess your going to need a line driver. You can always connect it up without the driver and see where your gains need to be on the amp to get acceptable sound levels. If its to low add the line driver. What are you using to drive the sub? I would bridge all 4 channels from that amp and use them for your front components and keep the rears and center channel on the OEM amp.

fwillis0323

This is the sub i'm running. http://www.polkaudio.com/products/dxi108. I'm running it with one of the rear channels from the previously mentioned amp. I'm not looking to wake neighbors, just to get a little mirror shake is enough. The fronts were added after the fact. Prior to the fronts, the sub sounded perfect for my wants, and still sounds just as well with the fronts now integrated. The road noise was present with only the sub hooked up and got worse after adding the fronts.

fwillis0323

Rather than continuing to beat this dead horse, this will be my new approach. I'll pick up a 2 channel line driver and install before the oem amp for the front channels, leave the front center stock and unmolested. Pick up a mono amp for the sub and use the oem sub signal for the mono amps input signal (not sure if another line driver will be needed for this, or if convertering the sub wire to RCA type). Use the 4 channel amp to run the fronts via input from the line driver. All I need now is confirmation that this is the correct approach.

pohljm

That is the way to do it. rears on OEM amp if you want some rear fill.

stvtec

iTrader: (2)

I don't think you're describing "road noise" at all, are you?

I used this LOC to install a sub in my car. It works great, and you can still control the aftermarket sub using the headunit's SUB control.

fwillis0323

Call it what you want, but it's there regardless. Majority of the sound imitates snow on a televison, alternator noise increases with RPM's (typical), then add in headlight hiss and turn signals as well. It's apparent that there is some form of interference.

heres a list of the items in hand and being installed -

*http://www.polkaudio.com/products/dxi6500
*http://www.polkaudio.com/products/dxi108
*http://www.polkaudio.com/products/pa660_4
*http://www.polkaudio.com/products/pa880

Plus new processor *http://www.pac-audio.com/productDeta...&CategoryID=28
I know its not a line drive, but from research and local install shop feedback it has the ability to take the muddy output source and remove any type of interference from the oem amp to provide a clean signal whilst retaining full oem head unit adjustability. It also provides and additional aux input if needed.

pohljm

You definitely do not need that 8 channel LOC. If you want to run a processor run a processor like the RF 360. people seem to have good luck with that one. there are several others to choose from. Have you researched any of the builds here?

99% of all shops will tell you that they have to take the signal after the OEM amp and run a processor to then eliminate the noise and boosting/cutting that was introduced by the OEM amp. They want to sell you products. It makes absolutely no sense to do that. take the signal before all the crap is added to it then you do not have to process it out. Use the processor with a clean signal to begin with.

As far as your noise goes you will probably eliminate it once everything is wired properly. power away from signal wires, etc