Basic diffusor design?

[Eric Desart]

Ethan since you qualify people who think that polys are diffusers, as bozos, I don't think you have any serious experience with polys.

And since you sell a Schroeder/RPG derived one, I don't think your comment is objective.
You also know that only few ever will ever have the possibility to compare representative situations, and then there are numerous other factors involved in a studio.

You hear indeed differences in the close proximity, which are explained by how they work.
Differences is no synonym for quality.
And in function of comb filtering, most related interference problems discussed in groups, situate below the frequency range covered by standard Schroeder like diffusers.

Hence unless you find some (neutral) papers handling this, it remains assuming.
There are lots of papers about psycho-acoustic stuff (that's also a science). I should like to see one investigating this.

[jayfrigo]

Originally Posted by Eric Desart

Ethan since you qualify people who think that polys are diffusers, as bozos, I don't think you have any serious experience with polys.

And since you sell a Schroeder/RPG derived one, I don't think your comment is objective.
You also know that only few ever will ever have the possibility to compare representative situations, and then there are numerous other factors involved in a studio.

You hear indeed differences in the close proximity, which are explained by how they work.
Differences is no synonym for quality.
And in function of comb filtering, most related interference problems discussed in groups, situate below the frequency range covered by standard Schroeder like diffusers.

Hence unless you find some (neutral) papers handling this, it remains assuming.
There are lots of papers about psycho-acoustic stuff (that's also a science). I should like to see one investigating this.

I really don't think Ethan was intending to make a sweeping indictment with the "bozos" thing. Proper poly use does not a bozo make. It seemed to me to be a casual, perhaps even humorously-intended comment in passing, or at least that's how I request it be taken for the sake of civility in the thread (speaking as moderator now). Thank you.

Back to being a participant, I'll accept your comment at face value that RPGs literature could possibly have some unintended bias, not to spend as much time on the drawbacks of QRDs. I certainly agree that there are as many to QRDs as to anything else, though each has different pro and cons. As you observe, different is not a synonym for universal quality, though one or the other may indeed be better or worse in a particular application.

A couple of points occur to me. First, their original QRD is 30 years old at this point, and they are active researchers and have of course made progress and learned much since then. Some drawbacks may have been little understood at the time, but are better understood now. They have also added much of value to the literature in that time, and while far from the only source of value, I still have to count them as one of the best on this subject; not the last word, but to given serious consideration.

I think they first were motivated by what they felt the best solution to a particular problem, and the commercial part came later. They didn't set out to design the worst one they could think of and then try to con the world into using it through marketing. The benefits they write about in their literature were probably what influenced them to make and market a QRD in the first place. But yes, they are unlikely to list the negatives in a cut-sheet.

That said, I still like and use both, but over time have developed opinions about when I prefer one or the other, and I don't use single semi-cylinders. Through experience using both in projects, and listening to them in lots and lots of other rooms, certain applications will bring one solution to mind while other applications bring to mind the alternative. Even so, there is crossover. To generalize examples for a moment, I like polys in larger rooms, often for ceiling diffusion if there is enough height so that they don't encroach too much. QRDs I often like in control room settings where the room is a bit dryer. I think the extra density in the decay can sound smoother sometimes. Of course you can't be right on top of them, and I still don't feel that polys or QRDs are exclusively for the applications above. They are just examples.

I also continue to make my original distinction about awareness of the drawbacks of a single semi-cylinder, and that arrays and more complex polys are good ways to minimize those drawbacks. The single semi-cyl distinction was a point worth making in a DIY oriented group because people I'm sure have considered using one (or used one), and with this knowledge, they can easily minimize some of those factors.

[Ethan Winer]

Originally Posted by jayfrigo

I really don't think Ethan was intending to make a sweeping indictment with the "bozos" thing. Proper poly use does not a bozo make.

Right, and to me, "proper poly use" precludes a control room the size of a bedroom. In a large space a wall of polys can break up flutter echo, and that's the intent of the polys shown in Everest's handbook. But these days a lot of people are recording and mixing in much smaller rooms than 40 years ago, and the treatment strategies are totally different. A poly near to a performer or microphone is no better than a bare sheet rock wall. Versus a QRD that is infinitely better. This is very easy to hear! Which was the point of my post yesterday.

So c'mon folks, get your noses out of the text books and use your ears.

--Ethan

[gullfo]

and then there is my super duper poly quadratic slat panel diffusing absorber.

[Glenn Kuras]

Originally Posted by gullfo

and then there is my super duper poly quadratic slat panel diffusing absorber.

Better known as the SDQSPDA. Now there is a name that will stick in your mind. . Wait just call it the The Duper.

Glenn