Since you're using active crossovers, you have to be careful to get the horn and woofer into phase alignment, which usually requires woofer delay. The job is done for you if you use an Altec passive crossover and mount the drivers with the factory specified offset; otherwise you're on your own. As an example, I need 0.97msec of woofer delay for the midbasses I use with 511 horns, with a voice coil offset of about 17 inches. I determined that delay by inverting the horn polarity and tuning for a good null at the 800Hz crossover.