My DG30 rattles a room more than my HXDA even though the wattage is lower. It's loud, but of course, it sounds best that way. The HXDA doesn't really rattle my room at recording volumes, unless I go overboard with volume. The DG30 shakes it at my usual recording volumes. Just the way it is.
The problem, of course, is that my studio's recording area has a drop ceiling; drop ceilings are notorious for rattling with amps, regardless of acoustical fixes you might have on hand, such as bass traps and wall absorbers, and lots of studio owners simply pull them out and install something else. But doing that would put me out of business for a few weeks, and I have projects to work on. Something had to give!
I have very good bass traps, and had good quality acoustic tiles I installed when I moved in. These ceiling tiles have a reasonable mass (mass reduces sound transmission), but they're not made to deal with the ceiling grid vibrating from SPL.
And I did have the cabs decoupled from the floor and on risers. Both speaker cabs sit on Auralex Gramma or Great Gramma pads, and I also use an Isoactoustics IsoL8R on top of the Pads under the cab. There wasn't much more I could do to isolate the speaker cabs mechanically from the structure.
I needed to find a cure.
I theorized that another layer of acoustical material on top of the drop ceiling tiles above the cabs would both physically damp the vibration and absorb additional SPL. So I cranked the amp, and walked around the room while playing, noting areas where I could hear the ceiling vibrating. All but one was right over where I set up the cabs typically. Makes sense, that's where the SPL would be highest.
As it happens, only weeks before I moved in a few years ago, a new ceiling had been installed with Armstrong 404b acoustical material.
However, I had it replaced with better looking stuff that was maybe less absorbent, but better at reducing sound transmission due to its mass. But there was an extra unopened box of the Armstrong absorbent stuff in the storage room, that has a pretty high NRC of 0.70. That's not bad for absorbing sound. I decided to try it, as it was already on hand.
I figured I'd simply lay it fiberglass side down, directly on top of the ceiling tiles I had installed. Easy as pie to do, though I should have worn gloves and long sleeves, I forgot how irritating that fiberglass can be if your skin comes into contact with it!
After cleaning up the room, I fired up the amp, and played with the volume. Eureka! At normal recording levels (pretty loud!) the ceiling did not rattle at all! Much to my surprise, my theory and plan actually worked! It only rattles at ear-bleeding levels at this point.
I figured if anyone else has this problem in their studio or music room, maybe I should share my discovery, so here it is: if your drop ceiling rattles when you play, add an additional layer of absorbent acoustical product and see if that helps.
I'm so darn pleased with my bad self!