mcamson

Problems:
1) Aftermarket rear component speakers sound worse than stock. Barely any mids coming out of rear speaker woofers. The sound is very faint and sounds worse than my stock rear speakers. I mostly hear treble coming from the rear tweets and is very harsh. (attenuation already turned down to -3db)

What I suspect:
a) rear speaker signal is very weak and is maybe crossed over by factory head unit
b) rear speakers are only getting 80 watts since they are 4 ohm, while front components are 2.7 ohms getting more since amp pumps 125 watts at 2 ohm (so around 110 watts).


2) Front speakers producing whining noise when volume is set to 0. Sound is present when engine is on or off. When revving, it doesn't get louder but frequency of sound slightly changes.

3) Bass thump when turning on radio or switching between FM and CD.
-My original 2-channel Boston amp didn't make this sound, but new Polk 5-channel is making the sound. The shop changed the power and ground wire from 8 to 4 gauge.


Details of System:
-Car: 2006 GS 300
-Factory Head Unit
-Factory speaker wires

-Amp: Polk Audio PA1100.5 (5 channel amp)
130 watts @ 2 ohm
80 watts @ 4 ohm
sub output 400 watts @ 2 ohm

-Front Components: Polk Audio MM 6501 (25-125 watts RMS) 2.7 ohm
-Rear Components: Polk Audio DB 6501 (10-100 watts RMS) 4.0 ohm

-Subwoofer: 12" JL 12w3v3

-Audio Control LC7 w/ipod AUX (active Line Out converter)

Can you experts help please? I had all this stuff professionally installed and the shop can't figure it out.

Brians650

iTrader: (1)

make sure the ground to the amp is clean (don't use a seat belt bolt or shock bolt go right for sheet metal)

The I would stop by walmart and grab 100' of the blue wire in the car audio section. 12 or 14ga will do the trick for speakers. then some 16 or 18 to feed the lc7

Rerun wires through the doors and to the rear deck.

run wires from factory headunit to lc7.

this should clear up any noise. now you just need someone who can tune.

mcamson

I will confirm how the shop grounded the amp.

As for the speaker wire, I don't think that is the issue since my other amp didn't make the sound. Maybe it's a bad amp? If I have the amp replaced for the same one, do you think it will fix the problem?

Brians650

iTrader: (1)

I would doubt it's the amp.... did you unhook the RCA's and see if there is still noise?

rmbhagwa

Sorry about that.

swtjlsy

iTrader: (6)

If you had it professional installed then the shop has to fix it. The ground is part of the problem, but why would you be asking people on CL to offer advice for something you paid to have done. Thats why you paid the shop to do right? Just asking. Plus were is this shop located at so I can make sure I never work there or go there for anything bad install.

Adik

iTrader: (3)

^^^ +1

if a shop installed it.. they should fix it

Big Mack

iTrader: (1)

Good description, gives a good place to start.

You eliminated (or should have) the crossover issue with the LC7, since it sums up the inputs to a full signal (save for the sub bass) if set up properly. The power issue is negligible, as it will yield less than a 1-2dB difference between the two sets if they have the same S/N ratio.

As for the speakers having very little mid, did they put baffles in? They need to ensure the woofers have a good seal to the door locations or they will not play much in the mid/bass ranges.

This does, indeed, sound like a bad ground as stated before. Different amps have different thresholds for their power supply tolerances, and apparently the Polk is a bit more picky than the Boston. The thump, I would attribute to a lower impedance on the input side. Not a tremendous amount you can do about it, but increasing the output of the LC7 and decreasing the gain may help.

What I suspect: these clowns told you they were professionals and they're not. They should never have let the vehicle leave with turn on thumps, speakers with incorrect sound, and alternator whine.

Big Mack

mcamson

I unhooked the RCAs and it still makes the noise. Any other ideas?

mcamson

Well, I didn't buy all the components, speakers, amp from them. I just had them install it. They've tried fixing it and have spent a lot of hours trying. They said that it's probably the amp.

mcamson

UPDATE:

I took it back to the shop and they solved the bass thump and front speaker whining noise. They switched out the amp and this solved the problem!

Sffd103

iTrader: (16)

sweet!!!!!!!!

mcamson

They summed up the front, rear, and stock sub output. Is this the ideal lc7 setup?

They didn't use baffles. What they did was cut out the factory speaker from the factory baffle. This is the same as the front speakers which turned out fine. Do you think it has to do with the fact that the rear speakers are getting 30 or so less watts due to being 4 ohm while the fronts are 2.7 ohm?

Also, I'm thinking the rear tweets sound so much harsher than the fronts because they're located right on the door panel which is near the ear if sitting in the rear. Any thoughts? I wonder if they'll sound as crappy if I switch the rear db6501 speakers to the ones I have up front; the mm6501.