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  1. #1
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    Default 2008 GXP Monsoon Audio Quality

    My GXP has the Monsoon system with single CD player. The system is totally stock factory. Audio quality is lacking in two areas. Most noticeable is that the midrange is not smooth. Listening fatigue sets in after only a short time listening to radio, XM, or CD. The center dash speaker appears to dominate the front soundstage. I've noticed a "buzz" from the center speaker that sounds like there is something vibrating off the cone, but I've pulled off the grille and find nothing there. My plan is to replace the center speaker, but I don't want to duplicate the sound quality of that component. Maybe some electrical resistance in series with the speaker leads would help remedy the problem.

    Secondly, the bass output from the rear 6X9's is very boomy--emphasis is in the 80-150 HZ bass range, with little or no output below those frequencies. I've considered replacing these speakers, but am aware there is an amplifier with built-in crossover powering these two-way speakers.

    In 2007, we owned a new GXP with the same audio system and I remember the same obnoxious sound. Power output is more than adequate--it's sound quality that's lacking. I also have a 1995 Buick Roadmaster wagon that has much better, easier to listen to, sound than the Monsoon system in my Pontiac. Our 2014 Chev SS also sounds much better than the GXP.

    Maybe I've not fiddled with the equalizer enough--I normally run the system "FLAT." That yields the least annoying sound.

    Has anyone experienced the same? Is there a solution other than new head unit and new speakers? I've not found an aftermarket radio that is compatible with the existing XM system.
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  2. #2
    GT Level Member wstefan20's Avatar
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    Default Re: 2008 GXP Monsoon Audio Quality

    You've about hit the nail on the head. This sound system produces power fine, but quality is garbage. When I had this system, I ended up dialing the rear back and installing a rear 10" sub with a small amp to fill in the low frequencies. Had a buddy of mine fabricate a custom housing that fit where our awkward trunk "cubbie" on the right hand side and it looked stock and never got in the way.

    It filled in the frequencies nicely and wasn't too loud. I'm not into super loud bass, I just want to hear the whole soundstage.

    All the wiring diagrams are free if you create a free AutoZone account. Just Google entertainment schematic 2004 pontiac grand prix autozone.

    I ended up replacing the center speaker and adding a filter for the noise. Though, in the end, I ended up running new speaker wires everywhere, used a 30 band eq, passive and active crossovers, and replaced all speakers so I went a bit overboard... Haha

  3. #3
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    Default Re: 2008 GXP Monsoon Audio Quality

    Thank you wstefan20. I guess I'm not the only one with issues regarding the Monsoon audio system.

    When you added the 10" woofer, did you leave the rear deck speakers intact? If you did, I assume you set the level of the added subwoofer high enough to override the 6X9's boom.

    What did you use for the replacement center speaker? What kind of filter did you add?

  4. #4
    GT Level Member wstefan20's Avatar
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    Default Re: 2008 GXP Monsoon Audio Quality

    I used a ground loop noise isolator like this: https://www.crutchfield.com/p_127SNI...c&awug=9023248 they're cheap and they work. You can either cut off the rca ends and directly splice in, or if you're feeling really fancy, you can grab a bunch of rca connectors like this: https://www.amazon.com/dp/B01LYV4AWL...a-348285775336

    For the center speaker, I just went with a 3.5" alpine I got out of the junkyard. Any 3.5" speaker will work fine. There's a few videos on how to replace them.

    I left the rear speakers in tact, I just ran everything through a 30 band eq, and passive crossovers, which is overkill. I limited my sub to around 20-80Hz and had the rear from 80-500Hz, front and center from 500-5000Hz, and tweeters to 5000 up. Passive crossovers are great for limiting the door and trunk speakers before the amp, and I used an adapter to splice in my sub before the amp and also used a passive crossover. The only place I ever use active crossovers is for tweeters. They are pretty cheap and work well, plus like the brand I got, you can actually tune the level some. I used the speakerwire to RCA adapters for almost everything so I could easily revert to stock if I wanted to.

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