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diffusers

4K views 7 replies 5 participants last post by  sleepwalker3 
#1 ·
are 1d diffusers generally considered superior to 2d diffusers for wall placement? and if you have ceiling diffusers?

or is the perceived difference basically insignificant?
 
#2 ·
What do you mean by 1d and 2d? If it's dimensions a diffuser must be 3d or it isn't a diffuser.
 
#4 ·
Any diffusion is better than none.

IMO what you want to do is start with absorption until it just about starts sounding dry, and then add diffusion, starting with the backwall, and then sides.

Diffusion adds ambience without comb-filtering, unlike a flat wall.

You may have to remove a few absorption panels if you ended up going too crazy with the cheesewhiz.
I'd recommend 2 2x2 diffusion panels for every 2x2 absorption panel that is installed. Any more then that and you'll likely end up with too much absorption and not enough diffusion.
 
#7 · (Edited)
Diffusion adds ambience without comb-filtering, unlike a flat wall.
diffusers create more reflections which create more comb-filtering (more dense and closely spaced "comb-filters").

sparse specular reflections (eg, incident off that of a flat, rigid boundary) superpose and yield sparse comb-filtering as evident in the freq-response (wider polar lobing). diffused reflections provide more dense polar lobing which implies the notches and peaks in the frequency response are more closely spaced and thus not as destructive.



add to this reflection phase grating diffusers also provide temporal dispersion - which reduces this interference further by delaying the reflections in time due to the varying depth of the wells.
 
#5 ·
#6 ·
are 1d diffusers generally considered superior to 2d diffusers for wall placement? and if you have ceiling diffusers?
1-dimensional reflection phase grating diffusers (of the QRD or PRD variety) with the wells oriented vertically generate diffraction lobes (spatial dispersion) in the horizontal plane and vice-versa.

2-dimensional RPGs disperse in both planes: horizontally and vertically.



as for selection, it is up to the designer to decide how one wishes to manage the indirect specular energy within the room and reintroduce it back to the listening position over time. the selection and subsequent placement of these devices is dictated by those design requirements.

in the case of 2ch stereo reproduction setups, you will typically see 1d diffusers on the rear wall/sidewalls mounted with the wells oriented vertically to provide horizontal dispersion (reflections) - which reintroduces indirect diffused reflections laterally for passive envelopment. a 2d diffuser would also disperse energy (reflections) to the ceiling and floor and thus lower overall gain (2d diffusers are inherently more lossy than 1d - so the diffused reflections will be lower in gain).

for surround sound setup, active sources (surround speakers) provide the envelopment so the strict criteria for 1d diffusers (to provide passive envelopment) no longer necessarily apply. 2d diffusers can be applied here to diffuse the high-gain sparse specular reflections incident from the active sources - which attenuate the reflections without completely absorbing them. this provides a neutral, controlled environment without being completely dead (and subjectively unconformable).


or is the perceived difference basically insignificant?
depends on the requirements for specular energy mgmt in the time-domain. 2d are much more lossy (higher absorption coefficient) than 1d. for example - blackbird studio C is designed around a fully broadband diffusive sound-field and the 47tons of MDF on the wall (PRDs) attenuate the indirect reflection by -30dB (effectively anechoic - even though the room is entirely reflective).
 
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