Horrible Rear Speaker Distortion
 

Hey Everyone. It seems the majority of people in this forum are a lot more knowledgeable in Audio than others I've joined/read so I figured I'd give it a shot.

First, I have an '03 Accord EX Sedan.

Here's my set up:
Alpine Type S Components in the front
Infinity Kappa 6x9s in the back
Rockford Fosgate p400-4 amp under the passenger seat
Stock stereo with LOCs

I got my set up installed (regrettably at Best Buy) last summer. I work there so all the equipment was about 70% off and the labor was about half what a regular employee would pay so I figured it wasn't a big deal.

I've had problems with my set-up from the get-go. For some reason, the rear speakers are extremely distorted. Mids and highs sound like crap and when the bass hits, it sounds like the speakers are blown, rattling, or "farting" for lack of a better word. This happens at all volume levels. The front speakers sound okay but the tweeters are a little screechy for my liking. I have a JL Clean Sweep on my way so hopefully that will fix that.

The reason I'm so confused is because I've tried pinpointing my problems and I can't... I originally started out with Alpine Type S (or R... can't remember) 6x9s in the back, replaced those with the same, and then got the Kappas. Had the same problem with all sets of speakers regardless of brand. They had the same sound whether they were mounted or not. I also tried plugging the speakers into the front channels on the amp to see if that was the reason--which it wasn't.

Then I tried plugging my iPod directly into the amp using a 3.5mm to RCA splitter. When I did that, the speakers gave off awful engine noise. It got worse in random spots throughout the car. The rear speakers were also really distorted.

The distortion happens regardless of what settings (gain, hi/lo freq) the amp is on and regardless of what the stock HU equalizer is set to.

The speakers work fine on a test bench as does the amplifier.

EDIT: Forgot to mention I replaced the amp once, too.

Sorry for the novel--just trying to be as detailed as possible. I don't want to take it back to Best Buy since they screwed up the install in the first place, scratched up my interior and the installer already tried diagnosing the problem for hours.

Could distortion be caused by improper grounding? Like I said, the it happens regardless of the source.

Any ideas? Thanks!

Sounds to me like your amp is too big or your gains are too high and it's clipping. Those speakers are blown, especially if setting the HP high doesn't help. The amp pushed them too hard and damaged the suspension, so that makes me think the amp is too big. Clipping usually burns the coil, but I would imagine is can damage the suspension as well.I'm sorry I'm not experienced at all with debugging an audio system as I've never pushed my system too hard, and install everything my self.

As for the fronts, if your crossover has an attenuator set the tweeters to -3dB. I'm not familiar with a cleansweep, but I don't believe it has an adjustable EQ like a processor.

How high was your gain set? If it was anywhere near the half way point, it was too high.

If you take your speakers out of the back deck and just lay them in the seat, do they still have the distortion?

Is it possible the installer left the gain up after he installed it and as soon as he played anything, it ruined the speakers? Like I said, that's my third set. I bought all three pairs in the same day because I figured I just got a bad set. Then I thought it was the brand. I really don't think the amp is too powerful. Here's links to my setup:

AMP:
http://www.bestbuy.com/site/olspage....=1170289779383
The Amp is only 50W x 4 RMS at 4 ohm. Here's a possible problem... The front speakers are 4-ohm while the rear pair are only 2-ohm. Would this cause any sorts of problems?

FRONT:
http://www.bestbuy.com/site/olspage....=1199494646605

REAR:
http://www.bestbuy.com/site/olspage....=1202650463355

Does the amp not have enough power? I'm so confused.

Thanks for the responses, though!

No that amp is not too big for those speakers. That amp if rated accurately will give you 100w on a 2ohm load. And yes if the gain was high enough he could have blown the speakers in 5 seconds. What do you mean you bought all three in the same day? Two pairs blew within a day? (Isn't that what a warranty is for?)If so then there is no doubt your gains are too high either on the amps, the LOCs, or both.

Well, he originally installed the first set. And I noticed something was wrong. So I went and grabbed another pair of Alpine 6x9s and those sounded exactly the same. So I decided I'd go to a different store and pick up the Infinitys since I'd heard they were better. Same thing.

The speakers have been making the same noise since the first second I've heard them.

I'll be doing more testing today... taking them out and what-not.

Are you using more than one LOC? If your only using one try swapping the inputs around at the LOC. If two try swapping the LOCs around. It could be a bad LOC, but I doubt it. Check the gains on the LOC and the amp, they should only be about an 8th of turn on the LOC, and about 1/8th of turn on the amp gains. Any more than a quater is too much, more than hal is WAY too much.

Well, I did some tinkering today. Turns out the infinity's were messed up somehow. Here's today's events...

I took out one of the Kappas and took it into Best Buy to have the installer test it out. He hooked it up to a test head unit and turned the volume ALL the way up and only highs came out. The HU is normally hooked up to speakers in the install bay and I physically watched him disconnect those speakers and hook up my Kappa...

So the Kappas go from playing awful distorted bass in my car to no bass at all on a perfectly working system. WTF.

So I switched out the speakers with some Alpine Type-S 6x9s. I know for a fact both LOCs are turned just about all the way down and I made sure the gain was down on the amp. I turned the volume on my HU up to about 10 and could already tell they were distorting. I even switched the wires around in case the installer accidentally switched some wires and the speaker was just out of phase. No dice.

I guess I'll wait for my Cleansweep and see what happens. I just don't understand how the speakers sound exactly the same regardless of what channel they're plugged into on the amp. The front ones sound just fine but I've noticed the tweeters clip a little above volume 30 with the gain barely up on the amp.

If I had to guess I would guess it's the LOC distorting your signal. Or it could be the amp that is causing the distortion. If it's not the amp the cleansweep prolly will fix this

So, in my fury and rush to get this problem solved while the whether was semi-nice, I purchased a CleanSweep off eBay for 90 bucks... Or so I thought. Turns out I didn't read the auction very clearly and ended up buying the CL-SSI accessory that is to be used WITH a CleanSweep. I just keep adding insult to injury. Anybody need a CL-SSI?