...I need some help. I've tried everything, I just don't know what is going on.

I drive a 2003 Coupe, and am trying to install one MTX Thunder 8000 12" sub, powered by a Kenwood KAC-7252 amp. The amp is rated at 570 watts RMS, 1000 peak.

The Infiniti comes with a factory Bose HU that has no RCA outs. It does however, send signal to an external Bose amp and that amp then powers the speakers. What I did for signal was quick tap into the rear deck outputs, BEFORE the Bose amp. This way I am not running a strong signal into my amp. I then take the signal and splice it onto the speaker level input harness. So that takes care of my signal. Oh, I am running the sub bridged.

To power the amp, I am running 8 gauge power and ground wires, with an inline 40amp fuse on the power line. This was all part of a Scosche kit. I am getting remote turn-on from the same place as my signal, from the Hu outputs, pre-Bose amp. This 8 gauge kit said that it could handle the kind of load that a 4 gauge could, that's why I bought it. In my last car, I had about 900 watts RMS between two amps running on 8 gauge with no problems at all, so this is why I went 8 gauge. That takes care of power.

Now for the problem. So, the amp is receiveing power and turning on and off at appropriate times. That seems OK. When the volume is low, then he sub seems to be responding correctly, no phasing issues. What happens is that any time I turn up the volume, gain, or input level (on the amp) then the amp cuts off. It gets very hot very quickly and then cuts off. I can get the sub to hit at maybe 1/5 of the power that I know is there, but then it just shuts off.

Any help is greatly appreciated, Iv'e been trying to overcome this problem for weeks! This is the third brand new amp I've tried on this setup, with no changes. I even hooked up my friends sub to my amp and it ran fine, and then hooked up my sub to his amp and that worked fine! There is some problem between my sub and my amp! Once again thanks guys/girls.

 

I have posted this on car audio forums as well, but nobody there really understands the situation because they are not driving G35s. Can anyone here give me some insight?

 

It sounds like you need a different line converter. For steros with the bose system different taps are needed if you tap before the amp or after the amp. Go to soundgate.com They will give you the correct one for your application.

 

I'd never heard that before. I'll check it out.

What about when I don't use a converter, and just run the speaker level inputs into the amp? That doesn't explain anything......

 

A few questions, is your MTX subwoofer a single voice coil or dual voice coil? If its dual voice coil what is the impedence on each voice coil? And if it is dual voice coil how are each of the voice coils wired? Parallel or series? Also I'm guessing the Kenwood amp is a 2 ch amp correct?

 

I just ran into this with my install. You will have to take the signal wires from the factory head (before the bose amp), feed those to line level converters and then RCA into your amp.

Our car has a common ground and when you hook it all up to your amp, you are creating a ground loop (through power ground, and the sound grounds as well). I spent about 12 hours on this problem, and the techs at Infinity (the speaker co) suggested that this may be the problem.

SImple test... grab an ipod (or the like) get a 1/8" cable to RCA, plug into your amp and go for a ride. The sound won't stop.

Good luck!
Peet

 

If your using the wires Before the factory amp, then you simply convert those to RCAs, Absolutely No convertors are needed.

As for your 8awg theory, you should be up to 4awg. Technically any gauge wire would "work", but between the power your using and the length of the run I would definately considering changing it.

 

If it is a signal issue and you dont want to use a cheap line-to-rca then I would suggest the Audio Control LC6.

 

I'm using a 29.99 converter from Crutchfield. The think is though, this problem arises even when I go straight into amp in the speaker level inputs, no RCA's. So I don't know if the converter is the problem.

The MTX is single voice coil, wired bridged from the 2-channel Kenwood. The sub is 4 ohms, and the Kenwood is 4 ohms when bridged.

Hmmmmm........This is really pissing me off.......

 

The problem is because you are running the signal through the Blose amp first and then to your amp. The Bose amp adds special equalization that decreases the low frequencies as you approach the upper limit of the volume control. This is probably to keep the cheapy paper Bose speakers from shredding and/or melting.

Take the Bose amp completely out and use it for a boat anchor or something and tap directly into the signal wires where it would normally go into the Bose amp. Then feed the signal to your Kenwood.