I had a customer come in wanting two sets of kicker component sets in his 2002 civic EX, no biggy.

Get the component sets all in, system sounds alright but almost like it's lacking the highs it should have.

His setup as it came in had a sony cdx-7700 or something similiar... had the rear RCA outputs tagged into the input of a kicker 12 band EQ, which then had all 3 pairs going back to the trunk. Front and Rears were plugged into a smaller MTX 4 channel amp, and the sub outs were hooked into an ample audio amp. The sub was a older Square solo in a huge box with a massive porting setup.. should have been louder than what I was hearing for sure.

The customer wanted to upgrade his 4 channel for more power output, so I try the Infinity 7540A... and get alot of engine noise out of the rear speakers. I switch the amp to a kicker 4 channel since I've had issues with those infinity amps with pretty much every install I've done. Kicker amp has no noise on the front components, but engine whine like a beast on the rear channels via the tweeters. That's when a co-worker of mine noticed the LP filter was on on the rear channel of the MTX that was in there, so we knew it was a pre-existing condition.

Pretty much I followed the usual steps... regrounded the cap/distribution whoever put the stuff in had done to a much better ground... upgraded the battery to chassis ground (which absolutely blows in those civics) to some 4 guage and actually stripped paint away from the factory ground bolt which honda doesn't do... unhooked the EQ and ran the RCA's right from the sony to the amps (which made the system sound 10 times better with more highs and the sub actually pounded then)... but the noise still existed only in the rear speakers. I even swapped the front and rear RCA's at the amp, still only noise from the rears.

What I finally did was hook the rear tweeters into the rear crossovers, and hooked those cross overs to the amp's front outputs, and ran the rear midwoofers dirrectly off the rear channel of the kicker amp with the LP filter on. Not the best thing to be doing but it works and got rid of the noise... but can someone tell me any other possible cause for the noise, and why it was always on the rear speakers even when the RCA inputs were swapped??

 

It sounds to me like the 2 rear ch. of the amp have a problem when the filter is not set to LP, but you say you tried 2 other amps with the same result. What I would look at next is how and where are the rear speaker leads run from the amp the the x-overs, and where are the x-overs mounted, [although you didn't say there was noise on the tweets when you wired them to the front outputs] how did you rewire the rear x-overs to the front outputs and the rear woofers directly to the amp? 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> It sounds to me like the 2 rear ch. of the amp have a problem when the filter is not set to LP, but you say you tried 2 other amps with the same result. What I would look at next is how and where are the rear speaker leads run from the amp the the x-overs, and where are the x-overs mounted, [although you didn't say there was noise on the tweets when you wired them to the front outputs] how did you rewire the rear x-overs to the front outputs and the rear woofers directly to the amp? 94 </TD></TR></TABLE>

Because of room limitations with his box and all I double stuck tape the crossovers to the bottom of the rear woofers. I used the existing lines from the 4 channel to run the crossovers at first, which were some of that 12 guage twisted speaker line (more used for sub boxes than for midrange but whatever )

The lines were run from the amp, up to the hinge near where the trunk spring bars are, and straight to the speakers. I re-did them so they fed into the crossover instead (obviously).

I can guarentee even when the previous owner had just the kicker 2 ways installed front and rear that the rear noise existed and that's why the original MTX had the LP turned on for the rears.

How I did the crossover thing is pretty straight forward. the front speakers lines were connected into the 4 channel already. Then I ran new lines from the front outputs of the amps to the rear crossover inputs. I hooked the rear tweeters up to the rear crossovers. Instead of connecting the rear woofers up to the crossover, I ran the rear woofers straight to the rear output of the amp. I turned the LP filter on, with the freq set as high as the kicker amp would go, which was 200 hz. I also adjusted the gain down some since the crossover wouldn't be there to help filter the subsonics out of the woofer (if those crossovers even do that.. which I don't know lol).

I tried two different Infinity 7540A's, the new Infinity 7541A, and the kicker amp, and the noise existed with all of them until I did that 'jerry riggin'. I can't say I've hit an issue like this before where either swapping the amp, upgrading the ground, regrounding the amp(s), or removing an EQ or some other extra processing unit didn't remove the noise... I'm just more baffled than anything and just wanted to know what I missed or what the heck was going on.

The *only* thing I can think of that I didn't try was replacing the headunit with an Alpine or something... but even if it was something with the headunits outputs you think switching the RCA's at the amp would cause the noise to move to the connected set of speakers, not stay at the rears...

 

Where did you swap the rca's at? At the head unit or the amp? If you swaped them at the amp and the problem still persisted through the rear channel then I would say it could be either the rcas or the head unit. If you swapped them at the head unit and still had problems through the rear channel then it is in the head unit. I think I said that right. LOL This is the hardest thing to track down...I hate doing it.

 

Try grounding the front RCA ground to the rear RCA ground. Sounds like they may be at two different potentials. Not a recommended fix just see if the noise goes away.

Did the front set of RCA's also go through an EQ? Did you try eliminating the EQ to see if the noise went away?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjr162 &raquo;</TD></TR><TR><TD CLASS="quote">

Because of room limitations with his box and all I double stuck tape the crossovers to the bottom of the rear woofers. I used the existing lines from the 4 channel to run the crossovers at first, which were some of that 12 guage twisted speaker line (more used for sub boxes than for midrange but whatever )

The lines were run from the amp, up to the hinge near where the trunk spring bars are, and straight to the speakers. I re-did them so they fed into the crossover instead (obviously).

I can guarentee even when the previous owner had just the kicker 2 ways installed front and rear that the rear noise existed and that's why the original MTX had the LP turned on for the rears.

How I did the crossover thing is pretty straight forward. the front speakers lines were connected into the 4 channel already. Then I ran new lines from the front outputs of the amps to the rear crossover inputs. I hooked the rear tweeters up to the rear crossovers. Instead of connecting the rear woofers up to the crossover, I ran the rear woofers straight to the rear output of the amp. I turned the LP filter on, with the freq set as high as the kicker amp would go, which was 200 hz. I also adjusted the gain down some since the crossover wouldn't be there to help filter the subsonics out of the woofer (if those crossovers even do that.. which I don't know lol).

I tried two different Infinity 7540A's, the new Infinity 7541A, and the kicker amp, and the noise existed with all of them until I did that 'jerry riggin'. I can't say I've hit an issue like this before where either swapping the amp, upgrading the ground, regrounding the amp(s), or removing an EQ or some other extra processing unit didn't remove the noise... I'm just more baffled than anything and just wanted to know what I missed or what the heck was going on.

The *only* thing I can think of that I didn't try was replacing the headunit with an Alpine or something... but even if it was something with the headunits outputs you think switching the RCA's at the amp would cause the noise to move to the connected set of speakers, not stay at the rears... </TD></TR></TABLE>LOL...It looks like people post before they read

You have done every thing I can think of doing, except wiring the rear amp outputs to the front speakers, [to see if the noise moves to the front]

With what you have already done, you would think the problem would have to be after the amp, even though you say he had the problem before, I would never recommend mounting a x-over to a speaker magnet.

I am as lost as you are 94

 

swapped RCA"s at the amp. There was an EQ which only had rear outs from sony running into it, then branched to the 3 sets. Undid EQ, still noise.. tried 3 different model amps, didn try running rear outputs of amp to front speakers though... but with 3 different amps I doubt it was an issue with the amps filtering.

Well atleast I know you would have tried everything I did, even if the noise is still there after all.

I hate noise issues too, and I bet the problem is with the sony head unit being sony and all lol.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">Try grounding the front RCA ground to the rear RCA ground. Sounds like they may be at two different potentials. Not a recommended fix just see if the noise goes away.

Did the front set of RCA's also go through an EQ? Did you try eliminating the EQ to see if the noise went away?</TD></TR></TABLE>

I did try using the ground loop isolators (ok audio transformers to isolate any DC path the the RCA's could be carrying). I did have the thought of using these RCA peices we have for our demo boreds.. pretty much you plug them inline and it has a ground wire connected to the outside RCA line.. was going to try using that to give the RCA's a common ground path on the outside line but figured that may inject additional noise from another source.

All in all, oh well. The customer was alright with my fix, he just wanted it to work. I just wish I knew what the people who installed all the stuff the first time did or what component was making the issue to being with.