Anyone knowledgable with radios and speakers?

[Vette73]

Now that I put everything back together--starter, coil packs, ported plenum , IHs I turned on the radio......

It's an aftermarket JVC ( came with the car) when I turned it on I get a VERY loud piercing sound coming from what I guess are the rear speakers.....It basically sounds like an air raid siren, very loud and can't be controlled with the volume button....Radio controls work but the sound does not go away at all..

Before I bring it to a radio place I figure maybe one of the members went through this problem...

Thnx John..

[secondchance]

Need a bit more info. Are you running OEM speakers and amplifiers? Are all speakers shrieking? Just the rears? Use balance and faders and check if any or which speakers are working.
My guess is JVC head unit was spliced into OEM CDM and your CDM probably gave up the ghost.

[Vette73]

Need a bit more info. Are you running OEM speakers and amplifiers? Are all speakers shrieking? Just the rears? Use balance and faders and check if any or which speakers are working.
My guess is JVC head unit was spliced into OEM CDM and your CDM probably gave up the ghost.

Have to check but pretty sure they are the factory speakers...I looked at it fast before so I have to check the balance over the week...

Sound is unbelievably deafening and can't be controlled with volume controls...

[G8nightman]

If you have a factory Amps they sound like they are bad it will cost you about 100 bucks to get refbs.

[secondchance]

Not necessarily. Cadillacs, Nissans, and Infinities of the era used the same amps. When removed from a Corvette - expensive. When pulled from the others - not so.

http://www.ebay.com/itm/Pair-of-Bose-Sigma-975-Front-Speaker-Amps-94-99-NISSAN-MAXIMA-INFINITI-I30-/331730835500?hash=item4d3cb2d82c:g:LjAAAOSwAKxWa5F 1

Above posting are fronts. Rears are about the same $25 to $50 each.

[secondchance]

Based on my experience, if amps are bad, particular speaker sound will be low along with popping sound. Bad CDM caused shrieking sound as mentioned.

[RussMcB]

A thought: It might be easiest to forego the original Corvette components and buy new speakers (and possibly amps). The Bose speakers are very good, but it takes a bit of effort to get an aftermarket head unit to work with the original speakers, sometimes more work than it's worth.

Having said that, I have an aftermarket HU with original speakers and I'm very happy with the sound.

[lisounds]

Go thru the settings on the JVC Radio.
if you had disconnected the battery during the plenum service
the radio may have gone back to its default settings

Is it from both rear speakers?
i can't see both amp going at the same time.

any problems with the front?

[White Bullet]

As far as amplifiers go here is my experience with them. When I first purchased my car the radio and speakers did not work. I pulled the radio and sent it off for repair. After the repair everything worked for a while and then the front speakers failed. At that time I decided to go aftermarket with a new head unit and aftermarket speakers. In truth once it was done I was never fully satisfied with it. Sold off the aftermarket equipment and sent the front amps off for repair. Installed the repaired amps and man the system sounded what I thought at the time was really good. Later the rear amps fail. So off to the repair shop and guess what? The repair shop called and informed me that they were not correct for the car however they were correct for a Cadillac. I talked to them about the differences and in general here is what was said. Each amp is tuned for the car and the placement within the car. Amps from other cars cannot be interchanged and have them expect to sound anywhere as good. Each car amp is made differently and will put out different signals based on several things: placement, cabin of the vehicle, speaker size, enclosure size and power. You should not mix and match Bose amps because there is on-board equalization, which means the soldered components on the board create the desired tuning specific to the car it was originally installed. We made a deal and they sent me the correct amps for the Corvette. Once installed the system sound much better than before the rear amps had failed. This is just my $0.02.

[secondchance]

Each amp is tuned for the car and the placement within the car. Amps from other cars cannot be interchanged and have them expect to sound anywhere as good. Each car amp is made differently and will put out different signals based on several things: placement, cabin of the vehicle, speaker size, enclosure size and power. You should not mix and match Bose amps because there is on-board equalization, which means the soldered components on the board create the desired tuning specific to the car it was originally installed. We made a deal and they sent me the correct amps for the Corvette. Once installed the system sound much better than before the rear amps had failed. This is just my $0.02.

I agree partially. First, C4 Corvettes have very little space up front to install aftermarket speakers correctly. I have seen some where 4" or 5" speaker was mounted on a flat plate cut out of MDF and bolted onto OEM front speaker/amp module location. Such installation will sound not that good because speakers need to be in a proper sized enclosure. Mounting on a plate creates a situation where sound wave from the front gets canceled by sound wave from the back due to phasing.

As for each amp being equalized based on different models and even coupe vs. convertible is true. This especially is true if using OEM head unit because Delco-Bose head unit has very limited equalization control. However, if using an aftermarket head unit with better eq. control, this is not a major deal. I sopped being fussy over "front" vs. "rear" and Corvette amp vs. Cadillac amp vs. Nissan amp. I've ordered 2 x Cadillac 100 watt Bose amp for my fronts.

[Vette73]

Go thru the settings on the JVC Radio.
if you had disconnected the battery during the plenum service
the radio may have gone back to its default settings

Is it from both rear speakers?
i can't see both amp going at the same time.

any problems with the front?

Yes battery was disconnected when I had the plenum off...When I hooked up the
Battery ( I did a few times because of additional repairs) it made that loud siren noise.......Honestly, this noise is loud and continuous ......Sounds like the start of a police siren that just keeps building...