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In Reply to: RE: Two kinds: posted by BigguyinATL on September 08, 2016 at 14:30:09
Polynomial is a new term to me. Though I KNOW it is a math term.
What I want to build LOOKS similar (but not exactly) and is called a 2D QRD.
I would think that as you DIFFUSE the back wave of the panel, you will also reduce its amplitude as you spread the SAME energy out over TIME.
I'm ok with that.
Too much is never enough
Follow Ups:
more attenuation occurs with w QRD panel because of phase cancellation. one portion of the reflected wave becomes 90 or 180 degrees out of phase with reflecttion from other portions of a signal.
The Drawback of one of these "stepped" QRD like panels when used directly behind a planar dipole that is parallel to the diffuser is that specific integer frequencies get attenuated or theoretically reinforced while other frequencies do not.
In most installations the diffuser is not going to be back wave.
The cheapest way to make non QRD style geometric reflective diffusers to make are plywood or particle board boxes. Vinyl lovers use the crates or boxes behind the speaker or angled against the wall and stacked on each other to the desired height. You can also build some of the cubes as a boxes with a damped tuned port to be a home made "tube Trap" helmholz attenuator.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
Fortunately, the panel and the diffuser are rarely parallel. In my case, they'd be offset by about 11 or 12 degrees. Panels are vertical.
The OTHER kind of diffuser I've seen is the 1D QRD, which is a big box with steps in calculated depths and all the same width. These can be pretty much as LONG (tall) as you wish. I don't have the facilities to construct these, since I'd need a good table saw and MUCH more construction space than currently available.
Calculators I've seen are 'seeded' with a Prime Number which may be key in avoiding 'cogging' frequencies.
How is a 2D QRD behind a panel any WORSE than the bare wall?
Too much is never enough
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