gm factory radio bass loss

Perhaps this has been answered already, but I could no find it via a search of the topics.

I've installed an amp and subwoofers in my 2005 chevy cobalt. The problem is that when the volume is turned up past a certain point, the bass signal seems to be automaticaly attenuated??

Has anyone found a way of over-throwing this problem? I dont partucilarly want to install a new head unit. To get one with all the features that this one has (MP3/CD player, RDS Radio, XM built in) would cost a great deal more than I can afford.

Thanks in advance

JD

stevdart hit it.  It sounds to me that you grabbed signal after the factory amplifiers.  I've read discussions about this on the impala forums somewhere.  The owners simply bypassed the factory amps, and all was good.  GM decided to attenuate bass when the volume is cranked to help prevent speakers from blowing.

tech460 wrote:

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The best way I know to compensate for this is to have a gain knob in the front and keep the gain on the amp and the LOC up fairly high. This way you can turn the gain knob down at low levels or crank it up at high levels. Keep in mind this is only a band aid to a solutionless problem. You are compensating for frequency loss and not gain loss.

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And a sure way to blow your speakers if you don't know exactly what you're doing.  I think this is a bad idea.  Gain is not a volume control and using it as one can cause your amp to clip very easily.  The only way to compensate for the bass atteunuation circuit is to turn it off (which can be done by the dealer in some vehicles, specifically Ford.  Don't know about GM) or replace the HU.  If the cut occurs in the amps as suggested above, bypasss them.  I suspect however that the EQ and volume controls (many cars also have speed-sensitive volume controls, another royal pain) actually are in the HU, but again I am not familiar with the new GM setups.  But please, set your gain properly and LEAVE it there.

Yes I agree with you DYohn and I could have went deeper in my post to explain that but I was just trying to give a band aid to a solutionless problem. I believe strongly in replacing the radio as what you start off with is what you end up with. Unfortunately, he does not want to do that. Please keep in mind that if my solution is done right it works right. I have done this many, many times with complete satisfaction and no blown speakers. It takes finnesse to get that happy medium.

Final words; Don't do my solution unless you are  experienced in gain setting.

Thank you all sooo much for your advice. I "grabbed" the signal just before the rear channel speakers. I did use a line level converter. I wanted to use the fronts, but there wasnt enough room behind the HU to install it. I thought perhaps the rear speaker channel was the problem. Im not aware whether or not there is a factory amp installed. I was under the impressino the only amplification being done was from the head unti itself. 

It would seem that you are correct in the fact that it is a solutionless problem though. Perhaps changing the unit out will be the onyl way to go?

Alomst all CD player's internal amps output from 16 to 18 watts continuous per channel or less. The only exception would be something like Alpine's V-drive built in amp or the Class T digital amp in one of Panasonic's head unit. If you bought a good quality head unit you would get a cleaner signal from its preamp outputs.

What I meant by 50 or so per channel is that most radios that wrongly use that max.  spec (RMS is usually around 18 or so),  are extremely high powered for a deck. It's seems there is a big difference when you step over 50 or so per channel. The Pioneer, Panasonic, JVC, Kenwood, and Sony all seem to sound so much more powerful than there previous 45 watt per channel siblings, IMO. Technology I suppose (MOSFET outputs and such) . But anyway, that's what I meant. 

Also, if you get a deck with sub out that would give you control over the sub. Definite plus.

I also have a Kenwood head unit (40x4) and 6 disc changer which I removed from my old car that I coudl put in. Only problem is, I'll lose the MP3 capability, XM, and RDS (the main reason I tried to hold onto the factory unit) Perhaps a powered crossover? Would that help at all?

I also heard that with some gm models you have to keep the factory head unit connected even if you install a new one?? How can I be sure whether or not my car ('05) Chevy Cobalt) is one of those?

I would sell the Kenwood units and purchase a new unit with MP3 capability and satellite ready input. Some units have RDS also, I believe Alpine units do and they will also do XM. Even if it is out of your price range I would save up, it will be well worth it.

Now as far as your other question about the radio having to stay in the car, yes it is partially true and this is a data vehicle with GM's new data system, LAN, but most of these new vehicles GM's producing nowaday's are getting smarter and not putting anything past the radio on the data bus (anything past the data bus after the radio no longer works) like they did prior. The only thing you will lose should be just your door chime and delayed accessory (R.A.P.).  Kinda sucks for some people but getting a better radio is well worth it, IMO. 

Now they do make harness' to retain the data functions and keep your R.A.P. and chimes, but not for the new LAN systems. So until that becomes available you will have to use a standard harness which Metra makes one, 70-2103. Your kit part number and antenna adapter from Metra in case you wanted to know is  99-3302 and 40-GM10. Hope this gives you some insight.

Ok, I know this is a little out there and such... But, well... You can't afford a like $300 HU or more for a good one... But you can afford a brand new car? Given the Coblat has like a starting price of 17k I think, but still, I can't really afford 17k and I don't have any bills really other than car audio. *thinks* This just doesn't add up...