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Originally Posted by terry j  So I get on a 'scientific/pro' type forum and ask 'which qrd should I use?' *I know qrds are the rolls royce, all the studios and all the scientific literature say so yeah??* and some guys get on and reply 'not really better'....threw me into a spin as it rocked my stable datum! |
Do believe the hype!
Polys are great for what they do but they're crude and simple devices compared to number theoretical diffusers.
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Originally Posted by terry j In the cox book when they give the example of the -1 of the barker code, well I guess a good enough word would be 'the inverse'..and stangely enough it starts behind the normal ones, ie goes deeper. Heck, may as well make all of them deeper and diffuse lower! if you follow. |
The reason is that the prime 7 QRD have a nice "free depth" bonus. The calculator says the sequence is 1422410, while the numbers in the math actually goes from zero to seven. So you get the performance of a seven deep diffusor with only 4 as the real depth limit. When you invert it, you'll have to invert it with respect to the real performance depth - the number seven.
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Originally Posted by terry j Me? meh, just build a single diffusor of a longer length (greater base number, dunno 29 instead of four sevens or whatever) and no repetition problem. Maybe it will be slightly more work doing 'one 29' than 'four sevens', but better results. |
That's the way to go!
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Originally Posted by terry j So my confusion?? It was only last night that I finally printed off the patent for the skylines and went thru it.
There is NO mention in it at all about well dividers! (will double check tonight), no mention that for ease of manufacture 'we leave them out' or anything.
So is the BBC paper talking about something different yet 'we' have comingled them? |
PRD's are much less sensitive to the lack of well dividers than the QRD's. Having dividers gives better performance of the PRD array, but then again, you'd need to have a bigger distance between the array and the sweet spot. Well-less also represents less of a reflective side area on the array, which may be an issue in some rooms.