AMROC for Dummies - need help

[klettermann]

I'm building a modest AV room and trying to get the best acoustics out of it within my size constraints. I've been trying to work around the "golden" 1 : 1.6 : 2.3 ratio. The room is in a basement space of 7.5H x 15W x 26L (ft). Obviously the ceiling is pretty low compared to the other dimensions, so I'm playing with AMROC to try to find the best compromise. I'd like to use as much of the space as possible yet preserve acoustics (contradictory goal I suppose), but I'm really not sure what I'm doing. Here's my thinking so far:

1. look at the modal pattern using my actual height along with corresponding width and depth dimensions per the 1-1.6-2.3 ratio. That would give me a space that's about 7.5 x 12 x 17.25 ft. Presumably this would be ideal given height constraint. But its leaves a lot of unused space.

2. See what happens when I play around with width and depth at fixed height and examine how that differs from "ideal" dimensions in case 1. Then, contemplate how much worse this would be compared to the ideal.

Does this make any sense? To repeat, I really don't know what I'm doing. FWIW, I've got a bunch of bass traps and I'm quite happy to get more as well as wall panels, diffusers etc if that would be helpful. Construction will be pretty standard 2x4 stud and sheetrock construction. I can use glue-and-screw wall construction if that would be meaningfully better. Speakers are large Magneplanars. Any comments or suggestions would be great. Thanks and cheers,

 

[Curvature]

I would hire a consultant, else maximize space and spend money on multisubs and room correction before treating too much. Unfortunately dedicated rooms are bare compared to living rooms, so some treatment is necessary.

Acoustic simulation is good only if accurate, and AMROC won't be able to model true vs. apparent acoustic boundaries (sheetrock will pass frequencies that concrete and brick will not), which are frequency specific, as well as phase shift when walls flex. All of that affects mode distribution.

IMO, golden ratio is not a useful guide. Too abstract due to the reasons above.

 

[alex-z]

IMO, "golden ratio" rooms are only useful if no acoustic treatment is present. Larger rooms are beneficial overall, it pushes the room modes into lower frequencies. Meaning the axial modes can be managed with multiple subwoofers, and oblique and tangential modes with 6-12" of porous absorption.

Standard 2x4 stud and 1/2" drywall construction is terrible for audio purposes. Spend the extra money to do staggered 2x4 studs on a 2x6 base plate, and use two layers of 5/8" drywall. Makes an incredible difference in low frequency isolation. Compliment this approach with a solid core door and weather seal.

 

[klettermann]

OK, thanks much, very helpful. In summary, what I take from all this is basically to ignore the calculators. And this, because no real-world room that I'm likely to construct will be acoustically good enough for it to matter much. Instead, focus on room treatments and positioning. This leads me to a couple further questions.

1. My understanding is that the staggered stud construction is mainly to reduce sound transmission to adjacent rooms. However, my room is in the basement with exterior concrete foundation walls on 3 sides. So is there any actual benefit to the staggered construction on those walls?

2. I'll certainly do the 2 layers of sheetrock, no brainer. I guess that further improvements could be made by using ASC Walldamp or Green Glue or whatever between panels. My main concern is more acoustics than sound transmission, apart from the ceiling.

Make sense? Cheers,