I'm pretty stumped. I've got an engine noise problem, but its only with the rear speakers. My front speakers are much nicer with a broader frequency and they aren't emitting any unwanted noise.

I guess I should say whats in my system to kill confusion, eh? Pioneer DEH-P510UB HU, Rockford Fosgate Power T152's in the front as well as factory tweeters, old Sony Xplods in the rear deck. Speakers (minus tweeters) are powered by a Rockford Fosgate 450.4 4 channel amp. Subs are 2 RF P3's powered by a RF 550.2 2 channel. Wiring consists of 2 gauge fosgate power and ground wire, 4 gauge fosgate wire going to both amps and the sub amp's cap, as well as the subs, and 14 gauge going from the amp to the four speakers. Tweeters are using the factory wiring and plugged into the HU

I just put in a new Pioneer HU today, replacing my old Pioneer HU. With the old Pioneer (with a ghetto fixed pico fuse) I had very quiet, almost unnoticeable engine noise from the rear speakers (could only hear it at REALLY high RPMS). Its a lot louder with the new stereo, and I'm thinking its because the old one had 2.2v preouts and the new one has 4v preouts. I also threw my sister's Sony HU and still got engine noise, similar to the old Pioneer's. so I think its safe to say the new HU is okay, it just makes it more noticeable that there's an issue. The noise also doesn't go up with the volume, the engine noise I've experienced before did.

No blown Pico fuse, I know not to do that. :P

I've tried different RCA's, no change. Its a pretty standard install, no stupid mistakes to my knowledge. Power and REM down the right, RCA's down the left. Both of my amps are chassis grounded to the same place, its a good ground.

Things I'm going to try in the morning are seeing if its the amp (really doubting it), grounding the HU better, seeing if its just a bad ground on the HU's preouts, double check my amp ground just in case. I'm also going to try hooking up different speakers, is it even a possibility that it could be the speakers? They're really crappy Sony Xplods. Would getting to polarity screwed up cause that? I'm pretty sure I didn't, but still, I'm open to testing anything.

Any other suggestions about what I should check?

 

With everything off, pull the RCAs from the amp, start your car, and go listen to the rear speakers. Do you still get the noise? Whatever you do, DO NOT hotswap your RCAS or let the center pin ground out otherwise you will burn yet another Pico fuse.

If no noise, try changing the HU ground. If you still have noise with the RCAs disconnected, you may have an issue with your amplifier. Years ago I had a 4 channel Rockford Fosgate amp that exhibited noise on channels 3 & 4. It was sent back multiple times, until I became fed up with it and just gave the amp to my cousin.

 

Alright, now I feel stupid. The RCA's connecting to the amp weren't in all the way. Problem solved.