Skip to main content
Avatar
Please consider registering
Guest
Search
Forum Scope


Match



Forum Options



Minimum search word length is 3 characters - maximum search word length is 84 characters
Register Lost password?
sp_Feed sp_TopicIcon
Diffusion distances
Avatar
Member
Members
Forum Posts: 2
Member Since:
August 16, 2017
sp_UserOfflineSmall Offline
1
December 6, 2017 - 12:20 pm
sp_Permalink sp_Print

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.

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
2
December 7, 2017 - 7:20 am
sp_Permalink sp_Print

K, You can use the QD – 11. Start the diffuser at 24″ from the floor and extend across the total rear wall surface.

Avatar
Member
Members
Forum Posts: 3
Member Since:
May 18, 2018
sp_UserOfflineSmall Offline
3
June 18, 2018 - 6:49 am
sp_Permalink sp_Print

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!

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
4
June 18, 2018 - 7:53 am
sp_Permalink sp_Print

C, Yes, it also depends on room width and length.

Avatar
Member
Members
Forum Posts: 3
Member Since:
May 18, 2018
sp_UserOfflineSmall Offline
5
June 18, 2018 - 7:56 am
sp_Permalink sp_Print sp_EditHistory

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 !

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
6
June 18, 2018 - 8:08 am
sp_Permalink sp_Print

C, It will work. Follow up and let us know what you are hearing.

Avatar
Member
Members
Forum Posts: 3
Member Since:
May 18, 2018
sp_UserOfflineSmall Offline
7
June 18, 2018 - 8:13 am
sp_Permalink sp_Print

Yes sir will do! Thank you!

Avatar
Member
Members
Forum Posts: 5
Member Since:
September 23, 2016
sp_UserOfflineSmall Offline
8
November 16, 2018 - 12:42 pm
sp_Permalink sp_Print

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.

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
9
November 16, 2018 - 1:00 pm
sp_Permalink sp_Print

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″

Avatar
Member
Members
Forum Posts: 5
Member Since:
September 23, 2016
sp_UserOfflineSmall Offline
10
November 16, 2018 - 3:23 pm
sp_Permalink sp_Print

Hey Dennis when you said 2 dimensional are you meaning running both vertical and horizontal say in a 14.5 by 24 inch rectangles

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
11
November 16, 2018 - 3:42 pm
sp_Permalink sp_Print

B, yes. build them 24″ x 24′

Avatar
Member
Members
Forum Posts: 5
Member Since:
August 19, 2018
sp_UserOfflineSmall Offline
12
November 18, 2018 - 3:39 pm
sp_Permalink sp_Print

Hi Dennis,

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

Avatar
Member
Members
Forum Posts: 5
Member Since:
August 19, 2018
sp_UserOfflineSmall Offline
13
November 19, 2018 - 7:21 am
sp_Permalink sp_Print

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.

Avatar
Member
Members
Forum Posts: 5
Member Since:
January 18, 2019
sp_UserOfflineSmall Offline
14
January 26, 2019 - 5:22 pm
sp_Permalink sp_Print

I’m planning to add diffusion also in my room. But I have question.
I’m thinking, what is happening to the frequencies above diffusor frequency range? For example QD-7 diffusion frequency response is 850 Hz. – 3,400 Hz. As I understand frequencies below 850Hz passes through the diffusor. But what is happening with frequencies above 3400Hz? Are there any diffusors that diffuse above 3400HZ?

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
15
January 26, 2019 - 6:23 pm
sp_Permalink sp_Print

T, Yes, our mini wood diffusers go to 8 K. Here is link: https://acousticfields.com/pro…..usor-wood/

Avatar
Member
Members
Forum Posts: 4
Member Since:
February 24, 2020
sp_UserOfflineSmall Offline
16
February 24, 2020 - 3:27 pm
sp_Permalink sp_Print

Hi my back wall is about 2 meters behind my listening position and i would like to ask if i should go with foam or diffusers.

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
17
February 24, 2020 - 6:02 pm
sp_Permalink sp_Print

G, What is the room size and usage?

Avatar
Member
Members
Forum Posts: 4
Member Since:
February 24, 2020
sp_UserOfflineSmall Offline
18
February 26, 2020 - 6:53 am
sp_Permalink sp_Print

Hi Dennis, my room dimensions are length 3.30m , width 2.88m and height 2.68m. My listening position is toughly at 2 meters in front of the back wall. Usage of the room is mostly dialogue editing and mixing for films and sometimes foley recording. I have treated the front wall (much foam in the center, bass traps(2+2 bass traps1m each in the 2 front corners) and the side wall ( mirror trick, foam in refllection points) and i would like to know if now i should go for the ceiling or for the back wall and what material to use. Thanks!

Avatar
Chief Acoustics Engineer
Forum Posts: 629
Member Since:
August 12, 2013
sp_UserOfflineSmall Offline
19
February 27, 2020 - 10:04 am
sp_Permalink sp_Print

G, You do not have enough low-frequency management for your room size and volume. Treating the corners is just a partial solution when the whole wall surface is producing the unwanted pressure issues. You will need the entire front and rear walls along with both sidewalls.

Avatar
Member
Members
Forum Posts: 4
Member Since:
February 24, 2020
sp_UserOfflineSmall Offline
20
February 27, 2020 - 11:26 am
sp_Permalink sp_Print

the back wall with diffusors or foam ? in the front wall i have placed 8 foams 30x30cm. Behind speakers i have basstraps. Can i send you an picture?

Forum Timezone: America/Los_Angeles
Most Users Ever Online: 158
Currently Online:
Guest(s) 8
Currently Browsing this Page:
1 Guest(s)
Forum Stats:
Groups: 4
Forums: 10
Topics: 610
Posts: 1647

 

Member Stats:
Guest Posters: 31
Members: 18743
Moderators: 0
Admins: 2
Administrators: admin, Dennis Foley