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Diffusion distances
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December 6, 2017 - 12:20 pm
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Hi everyone,
i plan to use some diffusion on the rear wall but have limited space between my listening position and the rear wall,probably about 3 feet.
Which prime number QD would be most suitable,are the QD7 and QD11 considered near field diffusers or is that something entirely different?
Once decided which prime is best could i ask would two of these on the rear wall be adequate for good diffusion?
Any tips or advice appreciated.

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December 7, 2017 - 7:20 am
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K, You can use the QD – 11. Start the diffuser at 24″ from the floor and extend across the total rear wall surface.

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June 18, 2018 - 6:49 am
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Dennis Foley said
K, You can use the QD – 11. Start the diffuser at 24″ from the floor and extend across the total rear wall surface.  

HI Dennis, if K only has 3 feet from back wall to listening position, the QD-11 required calculations are 1132/375 = 3ft, but you mentioned to add another 50% (+1.5) totaling 4.5 ft to develop correctly… has your calculations changed? could it be actually possible to have a QD-11 with only 3 feet apart from listening position and do we need to compensate another 9.5″ for the depth of the actual diffuse box? Thank you in advance!

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June 18, 2018 - 7:53 am
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C, Yes, it also depends on room width and length.

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June 18, 2018 - 7:56 am
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Thank you for the response Dennis, I also have 3 feet from listening position to wall in a small room… I was debating wether to build a QD-7 but after reading this I think I will build a QD-11, and hope it works! :) any further insight or recommendation will be greatly appreciated !

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June 18, 2018 - 8:08 am
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C, It will work. Follow up and let us know what you are hearing.

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June 18, 2018 - 8:13 am
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Yes sir will do! Thank you!

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November 16, 2018 - 12:42 pm
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I have maybe 18 inches behind me in a 140 inches long by 128 inches wide room, listening to Magnapans that are 53 inches out from the front wall….which prime # for diffusion on the front and which prime # for the back wall.

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November 16, 2018 - 1:00 pm
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B, Use two dimensional QD-7 for rear wall and QD-13 for front wall. The QD-7 is 4″ deep and the QD-13 is 12″

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November 16, 2018 - 3:23 pm
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Hey Dennis when you said 2 dimensional are you meaning running both vertical and horizontal say in a 14.5 by 24 inch rectangles

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November 16, 2018 - 3:42 pm
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B, yes. build them 24″ x 24′

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November 18, 2018 - 3:39 pm
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Hi Dennis,

I got about 2M listening position to the rear wall can I use the Prime 23 QD diffuser?

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November 19, 2018 - 7:21 am
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got it now Dennis after watching almost all your videos on acoustic diffuser placement, i have finally understood what prime qd difffuser to use… the quarter wavelength rule.. thanks a lot dennis. looking forward in building my first ever p23 diffuser which the plans i bought from your website.

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