Originally Posted by akebrake
What is your goal?
Global thermonuclear domination!
Err, sorry, had a movie playing in the background. No, I actually want to impress the chicks with the hugeosity of my limp mass. Oops, that's not it either...
I'm building these for a small room (3.7 x 3.3 x 2.4m) that I have been using for about 8 years as a mix room, listening room and booth. In the past, it's been fitted with minimal bass trapping and much of the diffusion and reflection has been random, due to the variable gear and stuff that was in the room. In spite of that, the room sounds very good and the mixes have translated pretty well, although there was a self-calibration phase required. So I know where the modes calculate to be but in actual use, it's the 250-500Hz region that needs the most help - and that's just my perception based on mix translation, reference recordings, etc. So, for example, 10 cm fluffy in 0.7 x 2 m frames in the corners tames the room pretty well. But I'm going to flush mount the monitors soon, add a cloud and make an RFZ. I know that will bring a huge change to the big picture of the room's acoustics.
Boggy's "My Room" concepts really peaked my interest, so I want to try a hybrid of that and to make some of my own (pseudo) air transparent diffuser panel designs to mount in a modular frame so pieces can be swapped out, moved around, etc. We plan to move out of this house in a couple of years so this will be a little research project making modular absorption and diffusion devices that will ultimately end up in a totally different space. Is that confusing enough?
To back up to the days of the dinosaur, I led a team that acoustically treated industrial and laboratory spaces that were, to be polite, "environmentally challenged". For example, we were fitting analytical instrumentation to large industrial reactors that synthesized polymers or pharmaceuticals or adhesives, etc. These were in huge, warehouse-type buildings that were loud, smelly, potentially contaminated with toxic crap and either cold or hot but never just right. So we began building modular enclosures so we could assemble them near the reactor and set up the instrumentation inside the portable room, install the instruments, then replace the modular room with a smaller enclosure and GTFO.
I got into limp mass vinyl sort of by mistake. In one one of these reactor mods, we had problems with a new, very expensive instrument and its manufacturer was not very helpful in resolving the issues. So we brought in an instrument that we knew was performing well to do some comparisons. We were fresh out of modular walls and had to have an adequate spray barrier at the least. Keep in mind that this was a polymer manufacturing plant and the warehouse next door just happened to have large rolls of vinyl that was filled with different minerals. We wanted to just hang some sheets of the vinyl as a spray barrier but knew it couldn't support its own weight, so we got a huge, heavy duty nylon tarp and laminated the vinyl to the tarp, cured it then hung the tarp/vinyl sandwich from the overhead steel. It was immediately apparent when you walked into the nylon/vinyl "room" that the sound of the facility was hugely attenuated. By no means anechoic, but the LF from the extruder (which had a cyclic, high force steel hammer) was cut by an incredible margin. A quick measurement showed that the sub 500 Hz region was quieter than in the modular room a few feet away housing the problem instrument. And keep in mind that the nylon/vinyl curtain was open to the ceiling truss structure: the opposite of air tight. From that point forward, I would watch for the opportunity to use nylon/vinyl curtains because they could be set up quickly as a first line of defense, then we could work inside the tent to set up our modular walls, etc. And the curtain would remain until our job was done because it really killed the noise.
Regarding the filling of Tim-style LMV bass traps, I've done a little testing but have not seen a huge impact. For a low resonance enclosure, I can see why some people don't add any rock wool or fiberglass at all. I like to pad the trap with dual density rubber/foam and load it against the room wall and I think the effect of that may swamp the effect of the filler but that is just conjecture.
Sorry for the ramble, more photos coming.