OK, Well I've done the code for subwoofer and centre channel output.

Subwoofer has a 40, 60, 80, 100 or 120 Hz 4th order filter with gain from -20 to +24db. Centre channel has a gain of -20 to +24db.

So Stu, I've done the software, have you got any hardware? ( just jokes). I am going to build that hardware we discussed to test it hopefully this weekend.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)