Which is better for a DBA (Swarm); powered subs or unpowered?

Remember, 2 properly positioned subs will provide very good bass at your designated listening position only, but not throughout your entire room.

DBA subs give a time incoherent mess everywhere.

The Dayton has no delay so there is time smearing. What you end up with is a fat, detail-less low end pillow.

For music, two subs correctly positioned relative to the mains for the main listening position are the most realistic.

Of course, if the mains are an incoherent mess spraying sound all over the room, who cares?

A phase control does not adjust the timing. If you are 10 feet from 1 sub and 5 from another there is a time delta between the arrival of the two wavefronts.

Some people like this fat bass. 

All-Pass phase controls operate at only a single frequency with varying degrees of shift across the passband.
For example, the control 0° position 90° frequency could be 2.5KHz and the 180° position 90° frequency could be < 5Hz.
See  http://www.ielogical.com/assets/SubTerrBlues/PhaseControl.png for how an All-Pass phase control affects frequency.  http://www.ielogical.com/assets/SubTerrBlues covers integrating bass properly.

Note that the phase is not constant across the sub's range. To have constant phase, you must have a delay line or physically move the sub.

Distributed bass arrays do not result in "fat" bass.

By FAT I mean that unless time correction is implemented the separate sub signals will arrive spread over several milliseconds.

The beater whack on a bass drum will arrive asynchronously to the head resonance, which will arrive multiple times. Depending on the room, subs and positioning, some may arrive before the beater and some after.

IMO, it's as unlistenable as MP3 which are only acceptable in mono.

Perhaps it's because I sat so long in a recording engineer's chair, but there is ONE spot that has the correct image. Period. I never worked in any studio where the monitors, if they were time aligned, were not aligned at the engineers seat. NO STUDIO EVER had distributed bass.

An All-Pass phase control alters the phase relationship between the frequencies passing though it relative to one another. Hence, the phase relationship to the mains varies by frequency.

Moving the sub physically or with a delay does not alter the phase relationship of the reproduced frequencies relative to one another. The phase relationship to the mains is altered by a constant for the frequency in question.

Moving a sub changes the room and main interaction. A delay or phase control does not change room interaction, just mains.

Mixing on headphones is a modern abomination. Headphones were only used to set up a cue mix. Ditto egregious nearfields like Genelecs.

1. I've never tested anyone who could not localize a 30Hz tone playing from one channel or another.

2. The reason low frequencies are summed is for stereo playback to keep the stylus in the groove.

3. Nope. If the bass is mono, it still bears a time relationship to the rest of the spectrum

4. Sound is sound and behaves the same across all frequencies. Waves don't collide. They pass right through one another. We may hear or measure a null, but that is a mechanical artifact. Move away from the null and the signal level returns to the same level.

5. If our brains summed and averaged, we would not be able to perceive low end at all.

6. never read that. Please supply a reference. Not by DBA advocate, s'il vous plait.

7. 200ms!?!?!? Surely you jest. That's almost a ¼ note @  120BPM.    Again, please supply a reference.

8. Again waves don't collide. They get absorbed.

There’s also no performance, imaging or quality concerns dependent on the direct bass sound waves from any specific, or combination of subs, arriving at the listener’ ears first.

If that were the case, one could place a sub anywhere in a room and hear no difference.

Subs are not brick wall devices. They output significant energy well into the mid-bass. If they are not coherent with the mains, they smear the impulse response.

Perhaps DBA work with time incoherent mains where everything is a huge bucket of mush and when crossed over below where there is any significant program, but with time coherent mains and crossed over much above 40Hz, they never can.

1. why would I lie? I’m not selling anything. I want to stop people being preyed upon by charlatans. DBA proponents are not charlatans, but neither are they correct as the the ability it to produce time coherent bass.

Re other frequencies @ 30Hz. You are correct.
30Hz level ≈75db 4m from sub at seating position.
Microphone about 10cm from driver as measured by REW.
60Hz 0.372% -49.3db
90Hz 0.063% -64.3db
120Hz 0.032% -69.8db
150Hz 0.020% -74.0db

4. Air is air. Sound moves through it. There is not enough energy imparted to have laminar flow.

8. Sound waves do not interact and sum. A microphone diaphragm registers 2 waves. If the waves interacted claimed, where there is a null, where did the energy go and how was it recovered for the peak a few feet away.

I have heard DBA, but the mains were so awful, the system was unlistenable. The mains were a well respected [ lord knows why ] ≈$15k make that spread the sound like mayonnaise.

I have a slight advantage in that I sat in the engineers chair and mixed. When the vocal extends between the speakers, the hi-hat is about 3 feet wide, the foot is pillow and the electric bass is a nebulous strolling conglomeration of frequencies, I suspect something is not quite right. Of course, it is possible that it is all the studio monitor systems were wrong.

People like speakers with terrible impulse response, ports, 24 midrange drivers, etc. They are free to like DBA. It’s just not and never can be accurate from a time perspective.

I’m not sure that there’s much benefit to actually being able to reproduce LF in stereo

On true stereo recordings in an ambient space, it is essential. One can do an experiment with a pair of subs with a couple of Y-cords. Drive both inputs on each sub from a Y-cord so L feeds L&R on the left sub and R feed L&R on the right. Adjust level to account for the extra signal. Now rearrange the Y-cords to drive each sub with both channels so the L goes to L and R goes to R on each sub.

The difference is easily heard.

BTW, CDs are mastered from the original tapes. The 2 channel masters did not have the bottom summed.

An ambient recording in one made in an acoustic space that is not treated do remove all reflections and does not have additional reverb added.

Like a pipe organ in a cathedral.

When it was over, he told us that was the most natural rendition of the tympani he had ever heard in any room at any audio show.

Tympani are typically tuned to about C3 ≈130Hz with a 65Hz sub harmonic. Not really much in the sub range.

That does not mean you can tell where the bass is originating absent knowing that the two sides behave differently.

By extension,1 sub at the same level midway between their normal positions, two subs with mono input, two subs with with correct input and two subs with reversed input will all sound the same?

Methinks, and knows, not! At least for subs XO ≈80Hz.