Time coherence - how important and what speakers?

If you mean digital "tricks", I think the best answer is that the value and limitations of any digital manipulations could be more easily ascertained if they were not trying to correct for things they should not be- like cone breakup, cabinet reflections, gross phase shifts, interior resonances- non-linearities which should not have been in the speaker design in the first place.

If you mean "servo control" of the subwoofer, I have not seen that applied yet to anything close to an already linear design (a well-behaved subwoofer driver and rigid cabinet). I also have never seen anywhere close to the best accelerometers being employed... so expensive! Again, we really can't hear all the benefits and the ultimate limits of servo technology.

Maybe someone who designs servo subs for a living can come forward and explain more on that subject. Anyone out there up to that?

Best,
Roy

Pardon my ignorance, but can one mainatin correct time and phase with 12 and 24 db octave slopes? Many seem to say the only way to do this is with 6db slopes. Are active cross-overs different in this regard? Can active cross-overs be time and phase accurate?

No. Yes. No. They could be with appropriate digital time delays (delays that are different for each frequency) built in. Those are available as studio-oriented x-overs with built-in adc/dac's.

Roy

Roy, your a prince. Thank you.

So why is audio staying in the dark ages with passive crossovers? Even a listen to Mackie HR624 active monitors?Shows what active croosovers are capable of. Something to do with not being able to pick your own power amp?
I will admit that passive ATC 10's with ATC $3,500 integrated may have sounded better than active 10's with built in ~$500 amps so the power amp must be very good to see the improvement. Obviously a single $3,500 could be better than 4) $125 amps and this could explain why.