Distributed Bass Array configuration

@millercarbon - Thanks for your comments.

Regarding sub phase, I have experienced its making a big difference in FR (measured and audible) between sub and main, but it’s easy to believe that with 4 mono subs not all set to the same phase, this would lose its importance.

I never thought of firing the subs into the wall. Interesting idea!

I do agree that with proper setup, subs can and should be undetectable, and I’ve accomplished that with 2 subs. Should be easier with 4.

I can imagine that using mono subs, one loses the need for symmetry, thus it should be easier to get smooth response.

Thanks again.

@hilde45 -- Thanks for asking; yes, I’ve got what I was looking for (and more :-)). There has been a wide variety of opinions, all worth considering. My thanks to everyone; even if my experience does not mirror yours, I appreciate the time and effort you took to share your thoughts.

I plan to review the entire thread soon and draw my own conclusions.

And yes, probably everything helpful that can be said has been said by now.

@mijostyn -- An interesting story. I must correct you on one point. An expert is more properly defined as, "Anyone 500 miles from home." If one doesn't tell you what you want, another will -- they are a dime a dozen. I know; I was one (in another field).

I also had a TacT (2.2X) and a pair of Apogees (Caliper Signatures), though at different times. Flawed pieces, wonderful in their ways.

With subs, I always have used DSP HP and LP filters and careful adjustment of delay (phase). I have never used a sub without HP-filtering the mains, so can't comment on that idea. In my current setup, no one can localize the subs: bass seems to come from the main speakers, even though the subs are behind (!) the listener, placement needed to fill a room-induced response hole.

Since posting, I've played with a single added mono sub, and it seems to get my setup from 90% to 95%. (Some might not find that enough, but life is getting shorter.) I am mulling over how to adjust its delay -- my electronics aren't set up to do that, but I hope a sub with a continuous phase control will work well enough.

@millercarbon  - I trust that my joking exchange about "experts" was not something you took personally. It surely was not aimed at any particular person.
I appreciate your contributions as well as those of others.

@danager -- Thanks for the link to the Geddes papers. I surely know the name, but I don’t think I’ve read anything of his.

@mijostyn -- I use Janszen Valentina P8 main speakers. In my basement room, they respond well to 20 Hz, but a room-induced hole at 40Hz necessitates subs. As you say, subs project more authority at LF, even though SPL may be the same. The two Fathom F112 subs are in the rear corners, next to floor-to-ceiling bass traps. That is the spot in which the 40Hz hole can be filled most reliably. I use digital crossovers at 80 Hz, mostly, done by an Anthem STR Preamp, far better sounding than the Classé CP-800 it replaced.

I used to adjust sub delays with an OmniMic2, but that broke. (Lesson learned: do not position measurement mics by grasping the wand and moving it.) In a stroke of fortune, I won a UMIC-2, so I am learning REW, which appears quite capable, if complex.

I sent the TacT 2.2X to a mod shop in southern California to have the SRC replaced with a more modern one and some other components swapped. Unfortunately, the proprietor never finished the work and never returned the unit (which five years ago, was in pieces in a storage locker somewhere). The Anthem is one of the newest generation of audio DSP devices, and unlike the TacT, and very unlike the Classé, I don’t hear any artifacts when engaging the DSP.

@noble101--  I am acquainted with Duke through other channels and have had some information from him since posting. I do agree about his extensive knowledge on this topic, through setting up systems in many situations, as well as design work. I have observed Duke help users like me, who are unlikely to be buying a Swarm from him, and I've concluded that he's not just well informed, but one of the real gentlemen in our field.

I also like hearing peoples' experiences in their own systems; yet, it is not always as possible to generalize from them as it is from those of someone who's done the same thing in varied circumstances.

@mijostyn - What ruled the Amethyst out for me was that it has a fan, which a couple of reviewers have reported hearing. In my very quiet room (~26 dBA SPL), any fan noise would be obtrusive. Since Trinnov is reputed to have the very best RCS, I wrote to them and asked if they might release a fanless version. They said no.

"All-Pass phase controls operate at only a single frequency with varying degrees of shift across the passband."

Yes, that’s because they are really delay controls, and a given delay is equivalent to different fractions of a wavelength (phase) at different frequencies. But as far as I can see, delay is what’s needed to align speakers that are different distances from the listener (and might have different latencies).

At least, that's my understanding of the situation.