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[joeq]

I see many commercially made diffusion products that come in a 24" x 24" squares,  often sold 2 or 4 to a package.     I also found  some DIY plans for units 24 x 24.

Let's presuppose a small to medium room with good bass trapping and proper absorbtion and so on.   Now we add 2 of these 24" diffusors on some flat wall.  

Would anyone even be able to hear the difference?  

It strikes me that diffusors are such passive devices that two  2 foot squares are just a drop in the bucket.    Am I wrong about this?     Does a little diffusion go a long way?   Is it a more-the merrier kind of thing?   can you overdo it?

How would you go about determining what percentage of the room's surface area should be actual dedicated diffusion devices?    What do those numbers turn out to be in good sounding  rooms?



   

[franman]

This is a great question... To measure it, you really need something like a TEF that does Energy/Time/Frequency tests... If you can see the return from the rear (diffuse) wall, you can start to quantify what levels we are looking for in relation to the direct signal.. I don't have the software with me right now, but I'll ask Lars to make some suggestions as to the level of the Return after the Intitial Time Gap... Relating that to a percentage of surface area is a bit of the design experience that I do more intuitively than mathematically. I've done it so many times that I look at the size of the room, the distances (and times) involved and I come up with a reasonable area for the main diffusor bank...Let me see if I can quantify this better and get back to this thread..

Lars... chime in please!!

ps: I do see way too much diffusion sometimes, and you certainly can hear it (IMHO)... yes, 8 SF of diffusors is probably a little light for a "small to medium" sized room.. Remember the affect of properly used diffusors is "envelopment" and it's supposed to be subtle.. It's not supposed to be an in your face return... That's always the way I've approached it.

Man.. you guys are getting good with the questions!!!

btw.. the 24x24 module is SOOOO popular because it fits into a tegular ceiling grid system... many of the products are meant to drop into such ceiling grids...

[joeq]

franman wrote on Tue, 12 September 2006 19:10

This is a great question...  Relating that to a percentage of surface area is a bit of the design experience that I do more intuitively than mathematically. I've done it so many times that I look at the size of the room, the distances (and times) involved and I come up with a reasonable area for the main diffusor bank...Let me see if I can quantify this better and get back to this thread.. ...yes, 8 SF of diffusors is probably a little light for a "small to medium" sized room..

Intuitive is fine with me,  all I am trying to do right now is get just the crudest grasp of the percentages required in the "ballpark" sense.  

If  8 SF (2 x 24" squares) is "a little light"  would 16 be plenty or are you jocularly understating?   In my mind I am trying to picture those little scale-model water tanks where you could watch the ripples propagate across the room.  I try to imagine what a scale model diffusor would do to the waves, but I am having a hard time visualizing how just a few of these make any difference.

 
I often see small studios with 2 or 3 lonely-looking diffusors pasted on the back wall and wonder if they aren't really in the "why bother?" category.   When I ask people about them they shrug and say 'they're expensive' as if the price was the limiting factor.  

I think there is a lot of good information out there about absorbers and where to put them, plus a lot of reasonably priced options for dealing with it.   It seems as if diffusion is more 'mysterious'  and the products commercially available are quite expensive per sq. ft.