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Which diffuser design for my room
Old 5th May 2020
  #1
Which diffuser design for my room

Hello gents!

I’m getting diffusers built for my tracking room, it’s 15x15 w 8ft ceilings. The absorption is covered with Gik panels. What I want is diffusion to get rid of the boxy sound. Which is recommended for this size room? I record Lots of percussion in this room. I ready somewhere that round half moon diffusers work best, is this so? Here is the link

https://www.acousticgeometry.com/diffusion-confusion/

Would any of these attached designs work?
Thanks!!
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Which diffuser design for my room-053c4fc8-f14a-4888-af36-0606a19e8d42.jpg   Which diffuser design for my room-0908495e-051f-4f42-962b-6e539eae3052.jpg   Which diffuser design for my room-3aaa5702-0af7-43a2-b22f-de9ca24042be.jpeg  
Old 5th May 2020
  #2
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Jens Eklund's Avatar
 

Unless very deep, diffusers (especially if 2D) will not do anything in the range normally associated with boxiness.

Use proper absorbers, pressure based if you want better low frequency performance and also avoid absorbing the upper range (that you might want to keep in a tracking room unless early reflection surfaces related to recording sweet spot), to tame issues in the lower frequency range.

Before even thinking about diffusers, please educate yourself on what they do and what they don’t, and how to use them properly in a room design. Here’s a start:

QRD Diffuser for Tracking AC Guitar
Old 5th May 2020
  #3
Hi Jens!
Thank you for your reply. My room is well treated like mentioned with Gik panels. I have bass traps in all corners, 2 super bass traps and 4 inch panels as well. I would like to liven up the room but I’m confused on which diffusers to use in my room. I’ll read your article to see if it helps.
Thanks
Quote:
Originally Posted by Jens Eklund View Post
Unless very deep, diffusers (especially if 2D) will not do anything in the range normally associated with boxiness.

Use proper absorbers, pressure based if you want better low frequency performance and also avoid absorbing the upper range (that you might want to keep in a tracking room unless early reflection surfaces related to recording sweet spot), to tame issues in the lower frequency range.

Before even thinking about diffusers, please educate yourself on what they do and what they don’t, and how to use them properly in a room design. Here’s a start:

QRD Diffuser for Tracking AC Guitar
Old 5th May 2020
  #4
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by vsthalion View Post
Hi Jens!
Thank you for your reply. My room is well treated like mentioned with Gik panels. I have bass traps in all corners, 2 super bass traps and 4 inch panels as well. I would like to liven up the room but I’m confused on which diffusers to use in my room. I’ll read your article to see if it helps.
Thanks
If your room sounds “boxy”, it´s presumably not well treated and need more treatment in this range (about 100-300 Hz or so if you ask me where the boxiness range is) and probably down lower as well based on your description regarding treatment. Minimum recommended depth for broadband panels is usually 8” among most acoustic designers, but porous alone (especially if recording space) is not a very well thought out treatment option. You should use primarily some sort of pressure-based absorber on most of the surface area in order to combat issues below the modal range whilst not overdamp the upper range. Also; you need to treat a lot of area in order to achieve good results, especially in the lower modal range.

More here:

Advice Wanted: Best Option(s) for Additional Bass-Trapping


About adding diffusion to “liven up a space”:

This is an extremely common unfortunate misconception. Unless replacing (or covering) existing broadband absorption treatment; simply adding diffusers to an untreated wall/ceiling will never ever make a space more “lively” since it will reduce the gain of possible reflections by partly absorption (yes; all diffusers absorb more or less, regardless of design and material used) and partly scattering the energy in one or more planes. A passive devise can never “add” energy to a space. It´s the total design (that might use diffusers if appropriate depending on room size etc.) that makes a room sound more or less “lively”. Again, check my links to learn more about this (ITD/ISD-gap).
Old 6th May 2020
  #5
Deleted 56021e5
Guest
In fact adding diffusers to a live space with flat reflective walls/ceiling will actually LOWER the RT60, not increase it !

This is not perceptible in small room acoustics but it is in large room acoustics.

The explanation is quite simple

a) Diffuse reflection spreads reflections to more surfaces

b) Most diffusers have some sort of absorption when compared to a flat wall.

As a reading I would suggest

https://www.catt.se/diffseries/index.htm

That is why using typical Sabine equations or other numerical approaches fails to predict RT60 in most spaces, particularly with uneven absorption and the main reason we use CATT as a modelling tool at our office.
Old 6th May 2020
  #6
Moderator
 
Northward's Avatar
Most people don't realise diffusion is a form of band limited absorption.
Old 6th May 2020
  #7
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by Deleted 56021e5 View Post
In fact adding diffusers to a live space with flat reflective walls/ceiling will actually LOWER the RT60, not increase it !
Yes, this was the point I was trying to get across. Thanks for clarifying.

Quote:
Originally Posted by Deleted 56021e5 View Post
That is why using typical Sabine equations or other numerical approaches fails to predict RT60 in most spaces, particularly with uneven absorption and the main reason we use CATT as a modelling tool at our office.
Yes, I find it unfortunate that RT is still a metric for evaluating the performance of critical listening rooms in AES/EBU papers (maybe they removed it now, haven’t checked in a few years), when it in reality says pretty much nothing about how a room “sounds” even if the values could be trusted (which they obviously can´t if “small” room). It´s been many years since I last payed any attention to RT values but instead focus on the ETC and waterfall plots (below the modal range).

Even if large recording room, I would still pay more attention to the ETC than RT values since even a large recording room is generally still too small for RT calculations to be applicable.

I actually tried CATT back in the days, but I couldn’t really see the benefits when designing studio sized rooms. Larger concert halls are another story, but I´m staying clear from that kind of work.
Old 6th May 2020
  #8
Deleted 56021e5
Guest
I only use CATT in live small rooms like large tracking rooms OR home theatres and basically only check for information 500 Hz upwards. I don't use it in control rooms.

You can however extrapolate ETC and tons of information from CATT, not just RT. I totally agree with you that RT is completely misunderstood and given too much importante in studio design.

Last edited by Deleted 56021e5; 7th May 2020 at 09:04 AM..
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