I haven't been on these forums for years and it looks like the old Regal GS forum is gone. Anyway, this just came up on a 2006 Grand Prix GT and I suggested the following. This may already be known by most but hopefully helps some.
SUGGESTION:
It seems most of the GM W-body vehicles end up needing the rear speakers addressed because the crappy rear paper cones fall apart over time being exposed to UV sunlight. This is true for both the Buick Regal Monsoon 4 rear speakers and the Grand Prix Monsoon 2 rear dual voice coil (4-wires each) speakers. I would suggest for the biggest bang for the buck, to replace just the rears with (2) 6 x9's and add a 2-Channel amp to the existing system. Intercept the right and left rear channels coming from the factory Monsoon Head unit going to the Monsoon Amp and run those through a 2 channel amp added to the existing system. In the end everything else from the factory system can stay in place including the factory crossovers in the stock Monsoon amp. This is only a budget upgrade and to addressed blown rear speakers which is the most common problem with these systems. Also add the ZZP Performance "Alternator Power Cable" or an equivalent at the same time.
I'm not suggesting this to the audiophile but as an alternative solution for those not wanting to spend as much to just replace the rear speakers and improve the sound.
NOTE:
On Monsoon-equipped Grand Prixs, the factory rear deck speakers are dual voice coil 6x9 models with one coil on each speaker powered by a subwoofer output from the Monsoon-only amplifier.
The factory amp sends bass and treble through separate sets of wires to these rear deck speakers, so if you replace them, you'll have two options for getting full-range sound to your new speakers: 1) bypass the factory amp; or 2) replace it with an aftermarket amp.
Hope this is helpful.
