Just a few quick questions for the pro's out there:

I am looking for a subwoofer box and 2 x 10" subwoofers for the Grand AM. The car already has had the factory Monsoon system replaced with an Alpine CDA-9856 head unit, 2 x Alpine SPS-13C2's in the doors, and 2 x Alpine SPS-69C3's in the rear deck.

With the space in the trunk, I am wondering if two seperate ported boxes behind the wheel wells would do the job? Possibly a single box with two subs just behind the seat with the subs facing the trunk lid?

If anyone has any advice for a proper box/sub setup, let me know.

Thanks.

I have never tried facing the subs toward each other behind opposite wheel wells, but You may run the risk of cancellation issues on certain frequencies (ie sound waves that hit each other in opposite phases causing diminished out put. This may happen only on certain frequencies based on different frequency wave-lengths that will hit each other in just the wrong way to cancel each other).

Ideally, the best performance will come with your subs facing the same direction so the sound waves join creating a stronger wave rather than cancelling each other out. So, unless space is an issue, put the subs behind the seat & aim them to the rear.

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Thanks. I have made my mind to go with a Kicker Comp 10" sub/box combination.