#1870066 - 01/10/08 09:34 AM
Square rooms and 38% rule
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bigearededdie
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Registered: 01/11/06
Posts: 92
Loc: Spain
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Assuming you have a square room, instead of placing all the equipment facing a wall, would it be a good idea to face a corner and sit at 38% from both walls at your sides?
That's more or less what I've done as the best I could think of.
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#1870820 - 01/11/08 11:24 AM
Re: Square rooms and 38% rule
[Re: bigearededdie]
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Ethan Winer
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Registered: 06/12/00
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Loc: New Milford, CT, USA
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Facing a corner is good because it aims side wall reflections away from you. The downside is that puts a focusing corner right behind you, making treatment there all the more important. And you need to treat at least half of those adjacent walls to avoid the focusing.
--Ethan
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#1870896 - 01/11/08 12:51 PM
Re: Square rooms and 38% rule
[Re: Ethan Winer]
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gullfo
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Loc: Old Tappan, NJ, USA
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and you want to trap at key reflection points on the side walls (of which there are now 4...) and as Ethan said, bass trapping front and rear.
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#1871158 - 01/12/08 01:27 AM
Re: Square rooms and 38% rule
[Re: gullfo]
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bigearededdie
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Gullfo, in the diagram you seem to have a pretty big corner trap. Is that totally stuffed? Is it just a porous trap or has it got a membrane too?
I've still got an unteated corner that needs finishing and I'd like the best possible and cost effective solution. I know the best thing would be to totally stuff it, but it also is the most expensive. Gosh! I simply can't make up my mind!
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#1871477 - 01/12/08 03:21 PM
Re: Square rooms and 38% rule
[Re: bigearededdie]
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gullfo
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Loc: Old Tappan, NJ, USA
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no, its shorthand for Big Ass Bass Trap® 
you could line the front of the trap and walls with rigid insulation and that will mostly suffice. if you can add hangers to it to increase the amount of trapping, thats good too. or you could put the rigid insulation on the front and line the walls with panel traps and hang from additional insulation in the middle. it all depends on how much trapping you need. if your monitors only go down to 50hz and the room only supports down to 40hz, then you can probably just straddle the corner with a layer of 4" - 6" rigid insulation.
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#1871756 - 01/13/08 05:41 AM
Re: Square rooms and 38% rule
[Re: Ydope]
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bigearededdie
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Pardon me Gullfo, but I don't think I quite understood your explanation about hangers and so (you mean hangers like the ones in my wardrobe?). My room has a 29Hz resonance, and even though my Tannoy Reveals don't go down that far, that resonance still gets excited with bassy sounds. So I guess I'll need a BABT then too!
and you want to trap at key reflection points on the side walls (of which there are now 4...) .... Hi, looks interesting! May I ask, why is that area at the top wall a key reflection point?
Yeah, please.
Maybe the drawing is just a sketch?
Getting back to my original question, the 38% sitting position is meant to be where the modal interferences are least damaging to coloration in a rectangular room. Would it be best to sit 38% from perpendicular walls in a square room?
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#1871770 - 01/13/08 06:05 AM
Re: Square rooms and 38% rule
[Re: bigearededdie]
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gullfo
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Registered: 03/30/04
Posts: 75
Loc: Old Tappan, NJ, USA
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hangers are hung rigid insulation or soft boards (like homasote) which have insulation wrapped around then. they increase the exposure of insulation within the trap and have some additional qualities for trapping which no one seems able to explain...
yes the drawing is just a generic sketch, it would help to know more about your room in order to determine where the 29hz resonance is coming from, it could be dimension/mode related or it could be something structural.
if you position yourself 38% from the front and/or side wall - that is probably a good starting point. 38% is just a starting point not necessarily the finish line. same for nearly any room square or rectangular.
to be complete, you would want to do some measurements of the response in the location as well as around the room to identify actual positions of mode points and standing waves. a more complete analysis could be done to determine what you might expect but if you already have access to the room then measurements are better. REW, ETF, RPG Optimizer, Dr. Floyd Toole's mode calculator spreadsheet, etc. are all useful tools.
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