Here is an interesting research discovery on diffuser panels that can allow them be 10x thinner with the same bandwidth (or go 10x lower in frequency with the same depth) as current ones. It's not a product yet, but it could be an interesting development to watch:
http://newatlas.com/ultra-thin-sound-diffusers/49942
 

makes interesting reading and probably a very applicable product, especially in home and project studio environments where room height is always an issue and mounting diffusers at the ceiling may not be feasible with currently available Schroeder type diffusers.

Yes agreed, and good point about the ceiling - my home project studio space happens to be vertically challenged.  I could sure use something like this, so I'll be keeping an eye out. Hopefully whoever picks this up will also care about all the other little things that make for a good pro audio product.

the main challenge with this new product is the same we see with shared air space for helmholtz resonators - the actually space behind the face plate is permeated so the actual effectiveness of the device is reduced - i.e. in a well based diffuser the wells are separated and have a specific response which overall provides for the diffusion and frequency range impacted. with the multiple openings the shared air space does not necessarily provide the same effect... that said, with enough math and precision build, it's possible they are useful. would require proper test data to see if its working plus is would be useful to see it in different mounting setups (flush, 4" gap, 16" gap etc) and the responses from those...  meanwhile, best bang for the buck is still semi-rigid insulation (say 3-5lb/ft3 and 4" thick) wrapped with cloth. adding some slats over the face of it can improve HF response and scattering. good overall LF response without a lot of expense...

Interesting insights Glenn - so if I understand correctly, each node is individually a little Helmholz resonator, and it's the way that the nodes couple in space that creates the diffuser effect? That would help to explain why a practical design is so elusive, because the interactions resulting from that coupling would be very complex indeed!
 
For reference, here is a link to the technical paper from the article:
https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.021034
 
On cursory review, it appears that their design is based upon simulations, using numerical sequences that randomize the phases at different frequencies. They do present results from both simulations and actual measurements, both for the (old) Schroeder and (new) Meta-Schroeder, along with those from a flat plate (response plots with line traces and points plotted, respectively.) The measurements seem to roughly agree with simulations, sometimes remarkably well (considering), and sometimes not quite so much. I did not dive too deeply into their measurement setups and methods, but like you say, the next big step would really be to translate these lab experiments into a real-world studio and then compare the results.
 
 
Anyway, Acoustics as a topic is fascinating to me, especially with the amount of engineering that goes into those simple-looking passive control devices like traps, diffusers, resonators, etc. I'm really more of a circuits/algorithms sort of fellow, so I basically have an armchair-distance kind of respect!
 

the RPG folks had created an approach to use a sequenced thin panel backed with absorption to create the phase (and hence diffusion) effect. and many people have used these successfully. the challenge becomes one where want mids to be diffused... depth is still king. http://www.rpgeurope.com/products/product/bad.html
 

Thanks for the link Glenn. That binary approach from RPG looks brilliant - for the highs at least. I wonder if their limitation in the mids arises because their method of distributing the holes leaves large areas without any holes at all, which increases gross reflection. (Just a guess, really.)
 

Hey Carlos, long time no see around these parts. All the best.

Hey thanks Mudgel! Nice to have a little time to drop through here again - and nice to see some familiar folks are still around too.
 
Edit - I mean, "Hi Mike!"