Calculating the angle of the side walls

There are several instances of control rooms with the standard 60 degree speaker placement that show slat resonator side walls angled at 12 degrees from longitudinal. There are also instances of control rooms with a 90 degree placement that utilize a 22.5 degree angle. (I looked or an example but failed to find the ones I had seen previously.) My control room will be built on a 75 degree placement. How do I calculate the correct angle for my slat resonator side walls?

Soundman2010 said : And the general rule of thumb for Reflection Free Zone, then, is that the angle needs to be calculated for each specific case, based on the speakers, room geometry, etc.

How exactly is this done? ADVthanksANCE -Jack (in Bastrop. Tx)

Is this going to be an RFZ design, Jack? If so, then the angle can only be figured out by "ray-tracing": Just keep on adjsuting the angle until there are no reflections anywhere close to the engineer's head, when seated at the mix position. 12° splay is for flutter echo, not for RFZ. 22.5° might be OK, depending on the size and layout of the room. - Stuart -

Thanks for the update. This is going to be an RFZ design, so the larger angle is what I will be using. I use Bryce 3D for my ray tracing. I put the camera at the listening position (LP) and make the slat wall a mirror surface to determine what reflections will be present there. At 17.5 degrees, the opposite speaker is only visible in the mirrored slat wall about 4 feet behind the LP. Should this angle be increased to make this reflection distance greater?

I just answered my own question, I think. When I tried the angle at 22.5 degrees, the spot where the speaker became visible in the mirrored slat wall was about 2 feet in front of the rear wall. Meesathinkin I have found my angle. Thanks for your input that will certainly help with achieving my RFZ. -Jack (in Bastrop, Tx)

Well, you CAN ray-trace like that, in the 3D animation sense, but that's not what studio designers really mean when talking about "ray-tracing". It is manual, done by hand, since you need to project several angles at once, and check not just the first bounce but also the second bounce in some cases. You need to be able to see the rays inside your model, so you can determine if the reflections are passing far enough away from the mix position. And you need to do it both vertically and horizontally, and for both speakers, going in both directions. Video ray-tracing doesn't reveal all of that, unfortunately, since you can't see the actual rays. Same name, different technique. - Stuart -