Aren't passive radiators out of phase?

Thanks for enlightening us on the subject Bear.

BTW, on my website there is a page with my version of subs with PRs, 18" PRs. Two per channel. I call them Quadripole, there are now some graphs and a better discussion than I had up a few months back... I do show the output of the PR and the woofer in separate graphs (iirc). I did not put up the impedance curves. FYI the pair (each channel) comes out now to 8 ohms... I can get some more "snot" if I rewire the drivers so that it ends up as 2 ohms, but I have to put back the Crown Macro Techs to drive that low impedance properly.

The cabinets shown are actually a bit too small - these are the original pairs that I built and they should have an extra cubic foot (a few inches back and one or two here and there gets you an extra cu ft!). IF it did have the extra foot the F3 would be at 20 Hz exactly and the overall response without EQ (I don't usually use any) would be a bit flatter...

_-_-

(Dickason's Loudspeaker Cookbook covers some of this theory, btw...)

Thanks Bear. I think I'm beginning to get it. The PR is tuneable with the volume of the cabinet (due to the compressing nature of air) and the properties of the PR stucture. I wonder, have there been any speakers with pressurized cabinets or maybe gas filled? ........ How about liquid filled (he,he)?

The Dayton-Wright Electrostatic speakers were filled with carbon hexafluoride gas. The gas is commonly used in welding. Nothing would impress audiophile friends like breaking out the tank of carbon hex and filling up the speakers. On the days that they worked anyway.

The volume of the cabinet is a spring - while the property of the PR is mostly mass. The whole thing is merely a relatively simple resonant system. Of course there are losses and interactions and the issue of "Q" (the bandwidth of a resonance compared to its maximum, etc. But when you are all done it is a resonant system, that's all.

As far as filling with "gas" (other than "air") that's not of much use as the cabinets are awfully leaky, even when sealed to the limit of your ability to seal them! The only effect that changing the gas - at normal atmospheric pressures - would have is to change the spring which would effect the resonance and of course change all the parameters along with that. But they all tend to change when you change the mass and you change the volume of the box, the driver, the stiffness of the PR's suspension, etc. So, there's probably not much benefit, if any, to be had there.

The Dayton Wrights used gas as a dielectric, without which they would arc through rather instantly. Btw, they also used an awful piezo electric tweeter, so go figure!

_-_-bear