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Thanks for this opportunity to reply to so many misconceptions

Posted by Duke (D) on June 2, 2016 at 14:55:20

In Reply to: "Once you go dipole you never go back." posted by MikeCh on June 2, 2016 at 07:17:53:

I'm not being facetious Mike, I really do appreciate the opportunity. Lots of people have misconceptions about multisub systems, and you've just brought up several of them.

"The "swarm" approach recommended by Geddes (and used by many before then)..."

I'm pretty sure Earl Geddes was the first. Can you tell me who was advocating and/or using four subs asymmetrically distributed as a means of smoothing the in-room response before Earl did?

"...dipole bass radiators deals with room modes better because it does not excite them to begin with."

Dipole bass excites all room modes, some more than others.

Room modes ARE NOT BAD... and it is having TOO FEW room modes that degrades the bass in small rooms because the resulting widely-spaced peaks stick out like sore thumbs to our ears. In a larger room, the modal peaks in the bass region are bunched up much closer together (like what we get in the midrange region in our smaller rooms), so that they effectively form a CONTINUUM. A distributed multisub system essentially replicates this advantage of large rooms in the modal region. And perceptually it is the in-room frequency response that matters most in the bass region.

"[Dipole bass is] also a much simpler approach, only requiring two "boxes" rather than six or more."

In practice four monopole subs intelligently distributed is plenty, and Earl Geddes can deliver smooth in-room bass with three subs each independently equalized in the digital domain using his proprietary algorithm.

Practical dipole subs need a lot of displacement to get down to 20 Hz, and that usually takes its toll on system headroom. And as a longtime dealer of high-end dipole speakers (SoundLab and Gradient), in my experience dipole bass excels at pitch definition and clarity but is subjectively lacking in impact relative to a good comparable monopole system. In my experience a good distributed multisub system is the equivalent of a good dipole system in pitch definition and clarity but retains good impact.

"Using many woofers requires a very low crossover point (greater group delay)"

Group delay doesn't come into play as far as crossover frequency goes. What does come into play is the need to keep audible upper bass/lower midrange energy out of any subs that are located well away from the main speakers. For this reason I recommend lowpass filtering the subs no higher than 80 Hz, and using a steep slope, or using separate amps for the subs in the front and rear of the room if the subs in the front need to be crossed over north of 80 Hz.

Typical group delay in the bass region, in and of itself, is of negligible audible consequence, but its effect on in-room frequency response is of consequence. However since subwoofer + room constitute a minimum-phase system, when we fix the frequency domain, we have simultaneously fixed the time domain.

Maybe I'm not understanding what you mean by "group delay" in this context?

(from another post) "Also, unlike some who have commented in this thread, I have no financial motivation."

Just for the record, my dealer and manufacturer status is disclosed in my signature so that has been out in the open all along.

I mentioned my product only in replies to misinformation where I needed to cite a counter-example. In this thread I have been promoting an idea which can be implemented many different ways.

Note that in my initial reply to Noah I offered to provide him with a DIY solution that would be within his budget. Where's the financial motivation in that? I wouldn't be selling him anything, but instead would be my spending time helping him. This is because I really believe the idea offers what he is looking for, given his set of requirements. Gosh, that's almost the sort of thing Siegfried Linkwitz might do!

Duke

Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

Edits: 06/02/16 06/02/16 06/02/16 06/02/16 06/02/16

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