OK, I've been looking around for info about the measured level of speakers at the crossover. I saw a graph that Wayne posted
here that showed the signal level being down 3 dB at the crossover frequency. I've always thought of the crossover point as the -3 dB point as well. However, I measure my mains rolloff as 6 dB down at the crossover point. I've also read somewhere that speakers should be 6 dB down for even-order filters, and 3 dB down for odd order filters. I'm not sure if I buy that...
Anyway, discussion on the above is welcomed.
Tonight, while playing with making an LFP out of my BFD, I was playing with the rolloffs for the sub, as applied to target level. There is no house curve loaded. By playing with the crossover slope, and cutoff buttons in REW, I can get the target level to appear as either of these; 3 db down at the crossover point (40 Hz) or 6 dB down at the crossover point. The target is 75 dB, no house curve, nothing but the target as calculated by REW.
???
3dbdownat40hz.jpg Graph 1: Target=75 dB, Crossover=40 Hz, Response Shown 3 dB Down at fc 6dbdownat40hz.jpg Graph 2: Target=75 dB, Crossover=40 Hz, Response Shown 6 dB Down at fc