Hi everyone, I was browsing around and I stumbled upon a picture of a Binary Amplitude diffuser, does anyone know how to make these, what are the calculations? Something similar to the GIK slotted scatter plate, I think it might be a solution for my small home studio room. thanks. Your help will be highly appreciated...

https://gearspace.com/board/studio-building-acoustics/646084-calculating-slat-slot-width-binary-diffuser.html

On 30/11/2021 at 9:59 PM, frankn said:

https://gearspace.com/board/studio-building-acoustics/646084-calculating-slat-slot-width-binary-diffuser.html

I've spent a bunch of time on Gearslutz/Gearspace over the years but hadn't come across this thread relating to BAD panels - thanks 👍

 

On 20/11/2021 at 1:19 AM, SLS Sound said:

what are the calculations?

there's not much that I've found for the design of BAD panels like there is for Quadratic Residue Diffusers (QRDs).

For QRDs there's the free tool QRDude https://www.subwoofer-builder.com/qrdude.htm

Amazing tool - hats off to Collo for creating it !

 

I started this thread ages ago on BAD panels searching for design criteria/calculations:

It didn't result in any firm design guidelines

 

@frankn's Gearspace link above had a nugget on BAD panels I hadn't come across before in post #51:

https://gearspace.com/board/studio-building-acoustics/646084-calculating-slat-slot-width-binary-diffuser-2.html

"In AES paper:
"Two Decades of Sound Diffusor Design and Development, Part 1: Applications and Design" by Peter D'Antonio and Trevor Cox, JAES Volume 46 Issue 11 pp. 955-976; November 1998
you can find information that strips (slats) for 1D amplitude grating diffuser needs to have a maximum width of half of wavelength of maximum working diffuser frequency."

So for 100mm slat width, that implies a maximum working diffuser freq of 1.7kHz - above that freq I'm assuming there's still scattering going on.

 

My summary of BAD panels is:

• BAD panels provide "some amount" of diffusion which is less than diffusers such as QRDs.
• The lesser amount of diffusion provided by BAD panels has pros and cons over say QRDs
• The obvious con is that BAD panels don't diffuse as much as QRDs, 
• A pro is that because BAD panels provide less diffusion, their minimum listening distance is less than QRDs (Cox and D'Antonio recommend QRDs have a minimum listening distance of 3 x the lowest wavelength diffused) - how much that distance can be relaxed with BAD panels is not defined 
• BAD panels are an excellent way to bring treble back into the room if during the process of adding enough absorption to the room to manage bass you've made the room "too dead" - you just add slats over your absorption in a BAD pattern
• 1D BAD panels are easy to DIY - just choose your slat width and flip a coin a bunch of times or use an MLS sequence (I sort of like the "flipping a coin" approach - it's your sequence)
• It's very easy to convert a 1D BAD panel with 50% absorption to a 2D BAD panel with 25% absorption by laying more slats at 90 degrees - 2D BAD panels with 50% absorption (the masks with lots of holes) are loads of work to DIY

Post #53 in the linked Gearspace thread says:

"binary diffusers are a balance between highly reflective (possibly resonant!) and totally absorptive surface. Binary diffusers aren't a best diffusers that is invented until today. They are needed when we make room (too) dead because room modes, to bring back some liveliness in room together with some level of diffusion, nothing "spectacular".... There are much better diffusers than binary types, but they are more expensive."

 

I agree with this.

My approach to room treatment is to target bass frequencies first - get the room's bass under control as the primary focus.

Targeting bass frequencies with absorption means placing absorption straddling corners - large and deep and gapped (straddling corners), and avoid placing absorption at lateral 1st reflection points.

With this approach you could still easily make the room "too dead" - adding slats in a 1D or 2D BAD pattern over the absorption will bring back the treble with "some amount" of diffusion without reducing bass absorption.

 

IMHO this is the key benefit of BAD panels - bringing treble back into the room "with some level of diffusion" after you've made the room "too dead" with absorption whilst getting the room's bass under control.

 

On 20/11/2021 at 1:19 AM, SLS Sound said:

I think it might be a solution for my small home studio room.

 

Is your room's bass under control?

What are your room reverb times like? - it's normal for RT times to increase at lower frequencies.

This is a great reference for the metrics you could aspire to (my room doesn't come close to this ):

http://www.acousticfrontiers.com/wp-content/uploads/2011/10/acoustic_measurement_standards.pdf

 

cheers

Mike