Quote:
I think of linacoustic as an available tool for treatment of one absorbtion spectrum. Just as Sonex is an available tool for treatment of a different absorbtion spectrum.
It's not a question of which one is right, and which one is wrong. They aren't even the only two. For starters there's lots of other manufacturers and materials (fiberglass, rockwool, cotton, polyester), and techniques (polys, helmholtz, tube, corner, wideband) and mountings (against the wall, out from the wall, over a corner, interchangeable boxes, shuttered, portable, hinged adjustable).
The goal is to:
a) get rid of first reflections
b) have absorbtion over the remainder of the room hitting your target Theoretical RT60 over as many frequencies as possible, certainly from 125hz to 4khz.
Foam: Sonex 2" 0.06, 0.25, 0.56, 0.81, 0.90, 0.91
(source:
http://www.aptcommunications.com/abcoef.htm ).
Linacoustic RC 2" (51mm) at wall 0.25, 0.66, 1.00, 1.05, 1.02, 1.01
(source:
http://www.bobgolds.com/AbsorptionCoefficients.htm )
For each frequency you multiply the absorbtion coefficient by the area of the absorber to get the number of sabins at that frequency. You want to have roughtly the same number of sabins at each frequency.
For a truely wonderful description (i.e. the whole book, over and over with examples and ideas and applications) of RT60 calculation with options, have a look at
http://www.amazon.com/exec/obidos/tg...glance&s=books
Your walls may already be giving you some bass absorbtion, and little high frequency absorbtion. For example, a wall might have the following absorbtion coefficients: 0.10, 0.08, 0.05, 0.03, 0.03, 0.03
Now that doesn't look like a lot, but you have a lot of wall, so when you multiply it by the area you get a lot more sabins at 125hz than you do at 4khz.
So something with the opposite absorbtion spectrum to the walls, like linacoustic or Sonex, could be used to balance that out. Obviously since Linacoustic absorbs more than Sonex, you will cover less wall AREA with Linacoustic to hit your target absorbtion than you would with Sonex.
The furnature and carpet and even the people in the room contribute to absorbtion in various frequencies. You can ignore the difference in absorbtion between buttered and unbuttered popcorn.
Similarly, carpet's absorbtion coefficients can be balanced by making a ceiling mounted ContraCarpet helmholtz absorber.
Once you get the sabins the same for all frequencies, then you add wideband absorbtion (0.99, 0.99, 0.99, 0.99, 0.99, 0.99) to get the room down to the RT60 you want. For example, if a stereo music Control Room should have similar RT60 times to a Home Theatre (because they are both 'listening rooms'), you may want to use the RT60 = 0.25 * (( ProposedRoomVolume / 100 m^3 ) ^ .3333
(source:
http://forum.studiotips.com/viewtopic.php?t=410 note, scroll down a bit and you'll see various room sizes already calculated in both metric and imperial)
Keep in mind this is just one approach for predicting possible future construction. I believe that the real experts (Dennis) do it differently.
Once the room is built, doing it by measurements is probably much better, such as using programs like
ETF5 to do measurements to tell you what is wrong and then build things to solve those specific problems, and then re-measure.
So, what I'm saying is, which one you should use, and how much area you want to cover with it, and on which surfaces you wish to put it (walls, ceiling), are dependant upon what the current absorbtion in the room is, and the room size (volume and dimensions).
