Why the fascination with subwoofers?

@rodman99999 used the term "tight" in regard to a subject near and dear to my heart, that of musical cohesion within the rhythm section of a band. That is one of the foremost criteria in assessing the quality of that section, and his use of the term tight in this instance was in regard to musical tightness, not bass tightness in a purely audio sense. However, the bass quality of a woofer or subwoofer can and does also effect the perceived "tightness" of a rhythm section.

One point about Ralph’s argument regarding bass tightness can be discussed in the terms speaker designers use: a woofer can be critically damped (0.7), over-damped (a lower number), or under-damped (a higher number). A designer who wants to get more perceived bass out of his speaker will under-damp it---at the cost of bass "looseness", while a designer who intends for his loudspeaker to be paired with a subwoofer may over-damp his speaker, knowing that the bass quantity sacrificed to achieve a higher bass quality will be compensated for by the sub.

An over-damped woofer may not reproduce all the timbre, tone, and resonance produced by a, say, upright bass, as the over-damping will mute those qualities. An under-damped one may produce lots of bass quantity, but it’s lack of bass quality may result in the loss of the touch and timing of the bass player (and the drummer's playing of his bass drum). That’s why the best speaker designers aim for the critically damped figure of 0.7, the optimum compromise.

@rauliruegas wrote, about the AudioKinesis Swarm:

"For a 10" woofer (as the four subs array posted here. ) is almost imposible to handled frequencies below 20hz at over 100dbs ( SPL. ) and with low THD kind of distortion."

I didn’t design the Swarm to go below 20 Hz, but several customers who have measured the in-room response report -3 dB in the upper teens. For deepest loudest bass at the same price point (three grand for the system), a single monster sub is the way to go. I have designed a Swarm that can do well over 120 dB at 13 Hz, but it’s not very practical and I don’t think there would be much market for it.

Each individual 10" Swarm unit can do about 100 dB at 20 Hz in-room at one meter without approaching x-max or amplifier clipping, assuming "typical" boundary reinforcement. I don’t know what the THD number would be, as imo that’s not a problem that needs solving.  The in-room frequency response is of vastly greater audible consequence as long as neither woofer nor amp is driven beyond its linear limits.

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My fascination with subs dates back about twenty-five years, to my simultaneous fascination with Quads and music with bass.

Duke

Hi @lewinskih01, you asked, "What is your point of view about time alignment of a SWARM or other DBA systems?"

Imo time alignment is at best a secondary consideration in a distributed multi-sub system, from a perceptual standpoint.

The ear has very poor time-domain resolution at low frequencies, and you are aware of Geddes’ thinking on the subject (which is based on AES papers). On the other hand the ear is very good at hearing loudness differences at low frequencies once the low frequencies become loud enough to be audible. This is why equal-loudness curves bunch up south of 100 Hz. A 5 dB difference at 40 Hz can be perceptually as big a difference as a 10 dB change at 1 kHz! The implication is that getting the in-room frequency response right matters more.

Also, since speakers + room = a minimum phase system at low frequencies, when we fix the frequency domain we have also fixed the time domain, and vice-versa.

That being said, imo you bring up something which intuitively makes sense: Preserving the initial pulse of bass energy, that which "whaps" you. It would seem that precise alignment of the arrival of the energy from multiple subs would best support that initial impulse, but how precise is "precise"? Within 1/4 wavelength? According to a paper I read, the ear cannot even detect the presence of bass energy from less than one wavelength, so the "precision" required might not be as great as our intuition would lead us to believe.

This is just anecdotal, but every time I have reversed the polarity of one of the four subs in a Swarm system, there as been a subjective improvement, despite the fact that the initial pulse has been obviously degraded.

This past October at RMAF an industry veteran manufacturer with decades of experience came into our room and played his reference recording of Fanfare for the Common Man. He said, "that’s what a tympani sounds like." He went on to say that our system (in a normal hotel room) did the best he had yet heard on that recording. We were using two amps and had manipulated the phase of the two left-side subs relative to the two right-side subs.

Now it is theoretically possible to use four time-aligned and equalized channels of amplification and achieve precise time alignment and excellent in-room response smoothness simultaneously, and this would probably be even better. But at the price point I’m working, focusing on room-interaction related issues seems to give good return on investment.

Once we relax cost constraints, it might make more sense to build a planar array into the front wall and a corresponding array into the rear wall, reverse the polarity of the rear wall array, and time-delay it such that it cancels the signal from the front wall when it arrives.

Duke