Non-parallel walls?

[freejeep]

Hi All,

How far "out of parallel" do walls need to be to make a noticeable difference is sound quality? Ie. reducing modals and such.

Thanks,

DonC

 

[Buckle-meister]

How far "out of parallel" do walls need to be to make a noticeable difference is sound quality? Ie. reducing modals and such.

If memory serves, one attraction of splaying side walls is that you tend to 'push' the room's modes further back into the room and thus hopefully further behind the listening position. That said, if memory serves again, I believe that unless you really know what you're doing, splaying walls just makes sorting out a room's acoustics more even more complicated than with parallel walls.

 

[Rip Van Woofer]

...if memory serves again, I believe that unless you really know what you're doing, splaying walls just makes sorting out a room's acoustics more even more complicated than with parallel walls.

Right. From all I've read it has little effect except to move the locations of the resonances around in unpredictable ways. Not worth the trouble. And it'll really p*** off your builder!

Stick with right angles and to tried and true methods of low frequency absorption: resilient mounting for the drywall, and/or bass traps of various kinds.

 

[Ethan Winer]

Don,

> How far "out of parallel" do walls need to be to make a noticeable difference is sound quality? Ie. reducing modals and such. <

There are two unrelated issues with angled walls, and neither is worth pursuing unless the room is fairly large and you're aiming for that elusive "last one percent" of performance.

The first issue is avoiding flutter echo - that "boing" sound you hear when you clap your hands in an empty room. To avoid flutter echo without using absorption, both opposing walls must be angled so the offset is at least one inch for every ten inches. This has only a slight effect on the room modes, and certainly does not reduce the need for bass traps. It does avoid the need for absorption on the walls just to get rid of flutter echo. But most rooms need absorption there anyway to tame excess ambience, so often this is of dubious value.

The second issue is that angled walls change the room modes. But again, it does not remove the modes - it just shifts their frequency some. This too is of little real value.

--Ethan

 

[freejeep]

Thanks for the info. I have been doin a bunch or research into the design for my home theater and this was one of the questions I couldn't find a clear answer for.

DonC