02 325i, Kicker 400.1 w/ LOC to 2 12" MTX

The subject is an 02 325i with amplifier in the LR quarter panel. Running Kicker 400.1 with LOC to 2 12" MTX subs in a ported box (TCE5512X2D. Yeah, realize it's underpowered, but should still hit harder than what it is. The subs are pointed toward the back of the car, and I do notice the bass just seems to get weaker as the volume goes up. I'm almost sure that this has the circuitry (if that is a word) in it that keeps the bass lower so no distortion happens as you turn up the volume. Any suggestions?

that kicker amp is good for those TCE5512X2D, it's not to much underpowered since it is a ported box and 200 wrms to each is more than enought to get them loud. about the distorion check your gain it's seems that you have it high, lower it a bit and see what's happen.

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Shaking The Neighborhood

The issue isn't power, because it don't matter where the gain is, as the volume goes up, the true hit fades. My personal car (04 Stratus) had the same issue and I cured it by switching to an aftermarket deck. I was hoping anyone could tell me of a way to get around it in a BMW, as switching out the deck can get pretty hairy. Any suggestions?

Actually Bimmers are typically not that hard to install decks into.  There are kits available for these cars, as well as harnesses too.

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My ex once told me I have a perfect face for radio.