Car Audio issue

[dasmikechen]

Okay, so I am not a professional installer, not even that accute at listening, but I like good bass.

I own an Evo X and was hoping the Rockford Fosgate system would meet my needs, but they did not. I decided to buy a discounted JBL MS-8 sound processor to process the sound post factory amp to all of the speakers, including the 10" factory sub. Had Best Buy install this. Sounded okay, but the bass just sucked and turning it up caused the sub to clip. I owned two 12" and an 800W amp so I decided to have them install that.

I pulled the factory sub and the next time I turned the car on, a whine was produced. The whine is not alternator based, and is present even when the head unit is off. I then took the car to Best Buy hoping they would solve it by attaching the subs/amp to the MS-8, but alas it did not. The only thing the guy suggests is trying to remove the MS-8 and see if the problem persists, but this would mean a whole install/uninstall of that unit. Is anyone capable enough to help me troubleshoot/diagnose my problem? I just cannot believe I have spent about $1,000 total and have a worse stereo system except the bass

Thanks guys, any help would be great cuz I think Best Buy is no longer willing to help.

Edit: also, Best Buy installed both my MS-8 and sub amp to the both terminals on the battery since the battery is in the trunk. Is it true that connecting to the ground on a battery is not a good idea?

 

[mndsm]

Yeah, best buy is morons. Your whine is probably a grounding issue caused by exactly what they did (Hooking pos. and neg. to the battery). take the ground for the stereo jargon off the battery, and stick it somewhere metal in the trunk. Probably help a ton.

 

[micahlarson]

I would reground to start.

find a place inside of the trunk and take fine grit sand paper and run it down to the bare metal. drill a screw through it with a washer and o-ring connector with the negative wire crimped to it. and there you will have a decent ground in no time.

it also could be poor rca connection

I would have to ask around a bit but I'm prety sure you can just tap the speaker wires for a line output give signal to your amp, which would let you know if the ms-8 is malfunctioning.

you could get a CHEAP scosche or dei one for 5-50 on amazon or even from best buy or mach1

 

[dasmikechen]

Thanks for the advice. I may try that, but I did a quick test tonight before going to meet. I pulled the RCAs off the aftermarket amp and plugged the factory sub back into its harness. Sound STOPPED. To me I would assume this means its NOT the ground, and somehow has something to do with the MS-8 and the factory sub in/out lines.

I wonder if I just unplug the sub input lines (from factory amp to MS-8) if that would solve the problem since the MS-8 I imagine just spits out low level sound to the aftermarket amp. I regret getting this overly complicated MS-8... *ugh*

 

[mndsm]

Yeah, if i'm imagining your stereo correctly, you already had sub pre-outs in the back of the factory H/U, which means you coulda used those to go to the A/M amp instead of the factory one, and so on.

 

[dasmikechen]

That would be far too logical wouldn't it? Unfortunately, the way Rockford designed this 'factory unit' the headunit itself only sends two low level outputs to the factory amp under drivers seat. So the factory amp parses this out into 8 channels, two front tweets, two front mids, 2 rear 2-ways, and a dual voice coil 10" sub. The factory amp powers all 9 speakers.

So, when installing the MS-8, each of these 8 channels went to an input on the MS-8, and without adding the aftermarket subs (was hoping the stock would be good enough with the MS-8), each of these 8 channels had an output. The sub clipped, so I decided to replace it with the aftermarket stuff I had, but instead of running just the speaker wire from the MS-8, I used two RCA outputs from the MS-8 to the aftermarket amp.

Somehow, aftermarket sub/amp aside, simnply unplugging the factory subwoofer at a harness by the sub causes the dissodence which occurs even when the head unit is off. I wonder if not having the sub connected creates a lack of resistance that the MS-8 wants, but I am not sure how to keep it from wanting it. I am hoping that just by snipping the dual voice coil channels in front of the MS-8, the problem will be gone. Least nothing is broken, yet.

 

[mndsm]

You could be on the right path..... almost sounds like it's a signal processing issue at the factory amp that the ms-8 doesn't like. And if it's feeding distortion/signal to the a/m sub even when the signal is off.... I wonder if there isn't something in the way the factory sub is design that has some sort of impedence that the a/m sub doesn't. Are they both the same ohm rating?

 

[dasmikechen]

Different Ohm ratings... so that could be it. But the MS-8 is sending signal to them in different ways. One is through amped by MS-8 (speaker wire to factory sub) and the other is low level RCAs to a/m amp to power the a/m subs. The weird thing is before i even wired up the a/m amp/subs to the ms-8 at all, the sound occured just from pulling the stock sub off. And even when the factory head unit is off, the noise is still audible. Makes me wonder if signal is coming from the factory amp even when the HU is off.

 

[mndsm]

That could be it too. Sounds like the factory amp is designed to accept one kind of signal and one kind of signal only, and when it's not seeing the right signal coming back, it flips out.

 

[micahlarson]

thats how alot of bose systems work where the signal get's all jacked if everything isn't there.
it also could be a power issue for the factory amp where it's still drawing power when it isn't supposed to be.

either way the only way to really get rid of it would be to rip it all out and do a rewire!

 

[dasmikechen]

So I called JBL for tech support, they were nice and helpful, tho hadnt heard of my problem before. They suggested the most likely culprit is also the negative battery terminal, so I will start there. Hope all goes well!

 

[mndsm]

Let us know, I'm quite curious. Cause it's either gonna be that or signal processing from the factory setup that's doing it.

 

[dasmikechen]

So I am about to call it quits. I tried ripping out all my trunk plastic to get at the shit. To that end I was successful. I moved the MS-8 ground from the battery terminal to a chassis ground, did not fix the problem.

I pulled the speaker wire inputs that lead from factory amp into MS-8, and the sound still persists. This to me means there is something funky with the MS-8. I called JBL direct, and said 'the only thing that fixes it is plugging the factory sub in, is there a problem running speaker wire to factory sub and RCAs to aftermarket' he said that it shouldnt be a problem just that you will not have independent sound leveling. So, as a last ditch effort I try throwing the stock sub on and listened to it with MS-8 power with all bass levels low. It still fricken clips, so there is no way for me to run the MS-8 and have quality bass without a insanely mind-numbing hum/hiss/whine.

So, like I said, I will be having Best Buy remove the MS-8, throw in a LOC for the a/m subs, and have an MS-8 and wasted install fees and nothing to show for it

 

[mndsm]

Bummer. maybe you can hock that ms-8 on CL and get a few bones back at least.

 

[dasmikechen]

So had to remove the MS-8. As far as I know there is nothing wrong with it and it just didn't play well with my setup. I have everything that came in the box and some shrink tube wrapped speaker wire for up to 8 channels if anyone is interested. I guess I will put up a F/S thread at some point down the road. Looking to recoup about $450 if possible.

 

[mndsm]

Does the a/m sub work better now without it?

 

[dasmikechen]

I was worried the a/m sub and amp would not sounds that great since it was being connected LOC, but the head unit controls for Sub Punch and Bass actually affect the subs heavily so I can adjust the bass to get a good bass level for many different types of songs.

I think this is largely due to the fact that Rockford Fosgate does make their own signal processor(s), the 360.1/2. So I like to believe some of that technology made it into the factory amp (similar to how BMW get the Harmon Kardon/JBL Logic7 processing). Anyway, I went the MS-8 route to avoid taking up the trunk space hoping that a DSP would correct the lack of bass and sound level capping, but it only made the bass worse.

In the end, I should have just thrown the subs in for $100. The sound is pretty much exactly where I want it. I think the only thing I would need to improve it would be better quality amp/subs but I have been carrying the ones I own for 5-8 years. So yeah, no idea what caused the problem, but in the end I have the sound quality I want just lost a lotta trunk space for it.