It has bandwidth from 100hz to 20hz.
Not from Josh's measurements, it doesn't. I would say closer to 80 than 100. Not really adequate to address the biggest sonic problem in the upper bass in typical domestic living rooms. In the typical (poorly-designed) home audio system, that's fine. But a system assembled with some thought and some understanding of the underlying acoustic problems inherent to small rooms, not so much.
What Brian Ding has written (when he's not flaking out and making simply bizarre claims, such as claiming the "quality" of the "interconnect" makes a sonic difference in subwoofers) is that the servo basically limits bandwidth to <100Hz.
I find your opinion (which I've read already at AVS) on "servo bandwidth" amusing considering you champion everything earl geddes has to say... and his choice of subwoofers is <i>acoustic bandpass</i>
There's no inconsistency there. Based on models I've done with the woofer he uses (B&C 12TBX100) and reasonable estimates of the chamber volumes, the bandpass subs he sells have an upper F3 of somewhere in the 130-140Hz range. That's a nearly an octave more on top than the Rythmik offers, per third-party measurements. That said, with the Aurasound woofers I'm using, I could not get the bandwidth to extend high enough to be useful to smooth out room modes. So I went with closed boxes and an electrical highpass instead. What I lose there compared to a bandpass sub is a good bit of passband efficiency. Arguably, I get somewhat higher distortion as well, because an acoustic BP filters out a lot of distortion products. (The audibility of the distortion reduction is IMO an open question. But the efficiency advantage of an acoustic bandpass is not.) At any rate, I mitigate the potential distortion issue by using drive-units with
exceptionally clean motors and well-optimized suspensions. So the concept is fine, but depending on the parts one chooses to use it may not be the optimal way to use them.
As for use of "bass traps" or whatever, anything that will actually work will be a gigantic eyesore and will have to be DIY simply because of the bulk of it. (Commercial "bass traps" are too small to be useful.) A better, and less aesthetically intrusive, solution, is mains stout enough to play without a high-pass (adding three pressure sources in the modal region) and careful placement and optimization of multiple subwoofers. Which, considering that in-situ they will be radically different in frequency response anyway, does not mean or imply
identical multiple subwoofers, of course. Identical subs all around will work, and properly calibrated can sound great. The only disadvantage to multiple identical subs is that one can generally get by with smaller and possibly cheaper subs in addition to one big sub. Also, smaller subs in the auxiliary roles may produce cleaner bass, just because they will be able to fit in locations that a larger sub cannot. I am assuming that one can take measurements competently, because the automated systems (except for JBL's expensive, hard-to-find, and otherwise limited in capability BassQ) do not set up subwoofers properly. Unfortunately, it has to be done manually, through iterative processes.
