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Just wondering..I don't think you can fit enough periods onto a box..but.
did anyone try this???
Follow Ups:
I think you are right.probably not worth the trouble. a well depth of 6 inches needs a very large box to fit. and then it has to work too.greetings
a friend of mine bought a centre speaker for his surround setup that had a back panel that had all these wierd shaped curves and spikes pointing into the cabinet, obviously to diffuse the rear reflections... the box was pretty small and was made from some hard plastic stuff, so presumably was pretty easy for them to make complex shapes out of it.. it also didn't have any stuffing in it, which would make the shape more significant..
the shape of the curves looked like it was computer optimised, which works for mass production items like that..I don't know that it would be all that effective in better designed boxes with stuffing in them.. but it seemed worth doing for them..
Kye.
IMO a good idea, the Kharma uses something like this.
Some of the posters mention that the small dimensions would make it less effective, this is WRONG, as the problematic frequensys are the same that a diffusor corresponding to.. say.. 1/2-1/8 of the box dept, would be most effective in.However, whatch out so the path from the back of the cone doesnt make two or more diffusor wells the same distance if you know what I mean.
A simply "try" would be to place the driver in the center of the choosen box, and then divide the back side of the box into four rectangular areas. Make "false" bottoms in thoose rectangles, calculated not to have harmonic relationship.
This would help spreding the energy in time, add some absorbtion and it would be effective I believe.
This would be a good idea in a twoway reflex loaded box, as you can have less damping material for the same reduction in ripple from the reflected backwave. Less damping means less losses in the helmholtz region.
Some of my thoughts..
/Peter
I'd actually been thinking the same thing. I am facing a situation where I'm going to have to turn my Carver ribbons into built-in monopole cabinets. The idea of making the back panel a QRD seemed worth investigating. There would be internal absorption as well, but if the reflected wave was also diffused, it 'should' help eliminate any artifacts from internal reflection.
I am leaning towards the same conclusion indicated by others, though - there probably isn't enough space to make it worthwhile. I have a 5-6' high by 2' deep cabinet to play with, though, so I might be wrong. Certainly, just using more internal stuffing/absorbing material would be cheaper and easier.
If you do mean the 'box' of a loudspeaker then I would think that the size of a conventional speaker cabinet would be too small to house an effective diffusor. The depth (front to back) dimension of a diffusor affects the lower frequencies with a deeper well providing diffusion at lower frequencies. The well widths affect higher frequencies with smaller widths diffusing higher frequencies. I would tend to think that with regular sized speakers, the small size of the diffusor inside would not be too effective for a broad range of frequencies.
I have heard from some folks who tried it, and they said that it helped some, but that it did not seem to do any more than just an angled panel inside the box.Most of the commerically available QRD type devices need some space for the diffusion to develop, and are depending to a certain extent on the sound not all coming head-on to the diffusor. Inside a speaker cabinet, there is no room for the diffusion to develop, the sound comes head-on, and the limited well depth will limit the range that it can do anything at all. A lot more cabinet complexity for very little gain.
Jon Risch
Jon Risch
You can build a QRD anywhere but the frequency range might not be useful for your purposes.What is a "box"? What do you have in mind?
Best regards.
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