Why is good, deep bass so difficult? - Myths and their Busters

Willemj wrote: "I have tried to imagine what is meant by fast or slow bass. It cannot be the speakers themselves for reasons that have been explained. My hypothesis is that what people are referring to is really the delay that is visible in waterfall graphs of bass response in real rooms: the reflected sound of room modes lingers on."

Yes!!

What the ear interprets as "slow" is all happening on the trailing end of the notes. It is ALSO showing up as a frequency response peak, as you are about to see (and, this is the key to the in-room bass puzzle):

Speakers + room = a "minimum phase" system at low frequencies, and what this means is, the time-domain response tracks the frequency response, and vice-versa! In other words, where you see a slow-decaying ridge of energy in a waterfall plot is also where the system has a frequency response peak!

It gets even better: If we fix the one, we have SIMULTANEOUSLY fixed the other! So if we improve the decay time via bass trapping, we have simultaneously improved the in-room frequency response. And if we improve the in-room frequency response via EQ or distributed multisubs or whatever, we have simultaneously improved the decay time!

So any talk about the bass "speed" of a small woofer vs a large woofer is coming from an incorrect paradigm. The correct paradigm is, the in-room frequency response is marching in lock-step with the in-room decay times. THAT is the only "speed" that matters in the bass region, and we can fix it by fixing the frequency response!

* * * *

In these internet forum discussions it can be hard for observers to discern which posts contain accurate information. I don’t open up my trophy case very often, but given the myth-busting theme Eric envisioned for this thread, I think it may be relevant: A subwoofer system I designed using the principles I’ve posted about in this thread received a "Product of the Year" award from a major magazine (The Absolute Sound, 2015). This doesn’t definitively prove that the principles I’ve described are correct, but it does raise the possibility.   If so, then credit to my teacher, Earl Geddes. 

Duke

dealer/manufacturer

Thank you, willemj. 

The amp I supply with the Swarm has a single band of parametric EQ, but most people don't use it.  The only time I've used it has been to extend the very bottom end a bit when all of the modules were in sealed-box mode,  in a situation where we really should have left some of the ports unplugged but the customer insisted they all be plugged.  We used a real-time analyzer but didn't save any of the curves.  I haven't heard from anyone who has made measurements with the parametric EQ in play.  I have heard from multiple customers reporting +/- 3 dB in-room across the bass region, with the -3 dB point clocking in a bit south of 20 Hz, without EQ.  

One of my customers had been using a Meridian processor that had been professionally calibrated for his previous sub.   He reset all the filters to flat and called in the technician after he had set up the Swarm.  After making his measurements, the only thing the technician did was adjust the level a bit.  No further equalization was needed.  Apparently the technician said he'd never seen anything like it, and he'd been doing this for many years.   

But it's not either/or!   I am sure the Swarm would work very well with EQ, especially something well thought-out like the Antimode, in part because the spatial variation (change in frequency response at different locations) is greatly reduced by the distributed multisub configuration. 

Duke

"Strokes of genius are rare in any field,
          but I think Milnes’ Torus qualifies”

 - Jonathan Valin, The Absolute Sound, 2007

Anyway if you make it you can try to be kind to me, even if you have to go  against your nature.