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How SQUARE is a SQUARE room? (1 Viewer)

Phil de Bruin

Auditioning
Joined
May 2, 2002
Messages
12
Okay - so if a room is perfectly square, or have one dimension exactly twice another - you may encounter resonances that may colour the sound. But just how 'perfectly square' does a room have to be?

Are we talking within a half a foot? An inch? What about if the room in question is pretty god damn square, but the wall protrudes in the middle due to a fireplace? How much difference is that going to make?

Comments!?? :)

/nightdog35/images/filmreel.gif
 

John Desmond

Stunt Coordinator
Joined
Nov 13, 2000
Messages
90
The closer you get to "square" the worse will be your problems. Same thing with multiple dimensions being multiples of each other. So a room that is 8*8*8 will be real bad. Since we're talking about long wavelengths, I would think the 8* 9*8 isn't going to be much better.
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
The room doesn't have to be square or have one dimensione exactly twice the other. Any rectangular room will have 3 axial room modes (plus a bunch of others I don't understand yet). The reason square rooms are said to be the second worst possible shape (cube being the worst) is now two of those 3 axial room modes are the same, resulting in one frequency and it's harmonics being boosted or cut twice.
 

Richard Greene

Stunt Coordinator
Joined
Mar 5, 2001
Messages
148
Example for 18' x 16' x 8' room

showing axial room modes up to 80Hz.):

565/18 = 31Hz (and 31Hz. x 2 = 62Hz.)

565/16 = 35Hz. (and 35Hz. x 2 = 71Hz.)

565/8 = 71Hz.

Assuming room modes are 5Hz. wide there is the potential

for boomy bass at these frequencies:

29 to 33Hz (31Hz. mode)

33 to 37Hz. (35 Hz. mode)

60 to 64Hz. (62Hz. mode)

69 to 73Hz. (71Hz. mode)

69 to 73Hz. (71Hz. mode)

Analysis:

The 31Hz. and 35Hz. modes are adjacent modes that may sound like one broad bass frequency peak from 29 to 37Hz.

The two 71Hz. modes are stacked = potential bass boom

The 62Hz. and 71Hz. modes are close enough so

they may sound like one broad bass frequency peak from

60 to 73Hz.
 

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