That got your attention, didn't it? Probably not what you think; I'll explain. A long time ago, I inherited a pair of stereo speakers from a friend who was moving. Two 10" woofers, plus the mid and tweeter components. The cabs were pretty beat and ratty, so I thought about building new boxes(no wonder he left them behind). As I pulled all the drivers and crossover out, I noticed that each of the bottom 10's had no magnet, just a frame and cone. This was my introduction to passive radiators. I really had little knowledge about the arcane world of stereo/hifi, it was enough to just keep up with guitar/bass gear. It just seemed to me to be a very inefficient way of projecting sound, but, whatever. Now, there have been times where I have seen 2x10, 4x10, and 1x15 bass cabs sitting on full anvil style cases, on their sides, not wheels(and not just sitting in the bottom tray with the wheels). I fully understand the idea of the absence of stage coupling in this configuration, but on the other hand, would a case, laying directly on a stage, act like a passive radiator to some extent, if enough low end frequencies where present(and yes, I get it that there might be efficiency issues)? Surely the foam inside would deaden some of the vibration, but I recently picked up a used road case that looks like it would fit an SVT head. Without the foam inside, it just barely accommodates my TC Electronics RS210. With the foam out, I'm in the process of spraying the interior with that Flex Seal(as opposed to spray-on truck bed liner)to give the cab the minimal amount of cushioning and protect the cab from scratches, although its finish is pretty tough(got the bottom tray done so far). So, am I high to think that the road case might vibrate enough to add to the sound, or is it negligible? With the case having the butt-end down and cab on top, it elevates it(the cab)as if there was another RS beneath, which is handy. Does any interior coating, be it that rubbery stuff or a harder plastic, thwart the vibrations? In a way, I don't see much difference between that and those band pass PA subs, but of course there's no port with a road case unless I just use the top shell(that would theoretically act like a bass drum, right?).