Diffusers - 7-root vs 23-root?

[tony22]

Anyone have comparative experience between these two types of diffusers? The 23-root types that I’ve seen look like the “random block height” type of panel, where the 7-root typically looks like the “parallel trough” style of panel. Are there scenarios where one is better over the other?

 

[GroovySauce]

Is "root" the same as "prime" diffuser? I have prime 23 and prime 7 they are based off a formula. The 23 is much deeper and diffuses lower than the prime 7. I'm not that knowledgeable about the differences.

 

[tony22]

Thanks Groovy. Yes, I think the terms are to the same reference. I‘d heard that a prime 7, given the sort of curved nature of its design, can produce a kind of “seashell” sound if sitting to close to them (within three feet or so).

 

[GroovySauce]

Seems we are talking about different technologies. QRD (Quadratic Residue Diffuser) uses prime numbers and a formula to calculate well depth. They are flat not curved.

The depth of well determines the lowest frequency that is diffused. The lowest frequency diffused determines minimum distance to listening position.

16” well depth 242hz is ~4.7' depending on who you talk to you want 50% on top of that for the waves to blend. In this example you want to be around 7' away from the diffuser.

7" well depth ~550hz you want a 3' distance.

I have not experimented sitting close to mine. My 23 are 16" deep and 7 are 10" deep. I'm 9' 8" from the diffusers on the rear wall, measured from the closer side of the diffuser.

http://www.digitalaudiorock.com/cgi-bin/qrd.cgi <- diffuser calculator

http://mcsquared.com/wavelength.htm <- calculates wave size.

Edit: changed ‘ to “

 

[tony22]

Thanks Groovy! This will help a lot.