So with the 2 way install you are eliminating the tweeter in the sail panel? I think that would make good sense. I played around with tweeter positining in my previous ride (97 Saab 900). In the end I had tweeters cut into the door panels as well as a CDT upstage kit on the dash. It sounded real nice. I will not be cutting the door panels of my X5.

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2004 BMW X5 3.0i - Mine
2011 BMW 328i xDrive - Hers
2002 BMW 325xi - waiting for a new owner