bstan:
a vented enclosure will benefit with a 2nd order high pass filter before the amp, but...the high pass frequency and the Q must be very specific to the driver/enclosure, otherwise, you'll get a huge bump or hole (depending on the Q of the high pass filter, which is not published by any prepro man. that i know of, and therefore not predictable) at crossover point. give me your driver parameters, enclosure volume and vent specs and i'll e-mail you the graphs at all crossover points available on any prepro.

i am aware that there is an active crossover "splitting ALL THE BASS going to the main channels between the mains and the sub(s). to make it simple, take a low E bass guitar signal (approx. 42hz.) that is mixed into the lfe channel. simultaneously, there is the same key struck on a piano that is mixed into the L&R surrounds while a midi kick drum of approx. the same frequency is mixed into the mains. all three signals are now summed and directed into the sub(s) slipping under the 60hz. low pass point....double bass (actually, triple bass). not to mention, the producer's meticulous efforts are negated.
some of the harmonics of those 3 occurrences of a 42hz note remain where they are supposed to be (in this case, above 60hz) and may give the illusion of being correctly placed, but the whole idea of discreet music formats is null and the bass is muddied, exaggerated at the crossover point and out of phase.

the phase problems come from the summing of the bass signal of channels with different high pass points (ie, center at 100, surrounds at 60, mains at 40) with the lfe signal. read the article brianca provided the link to above.

as to the timing problem in my setup, it is not so easily, yet definitely corrected by a delay adjustment at the sub's crossover. (remember...the same delay problem exists within the design of most main speakers and is not adjustable, but that's another discussion in itself)._



[This message has been edited by bossobass (edited October 12, 2002).]