DIY Bass Traps and membrane or diffusion of some sort?

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Lkdog

This is my third post on my remodeled basement setup.
1) The folks here helped with my speaker placement and suggestions about room treatment.
2) The second post was about a soffit that runs across middle of the room and it was suggested that GIK consult.

I did consult with GIK Acoustics and although they have appear to have wonderful products the wait time is about 7-10 weeks right now.
They suggested starting with corner Bass traps and treating first reflections.

I decided to build my own Bass Traps after looking at a lot of different options from the usual suspects.
Basic design is 5.5' X 2.25' rectangle with 6" of compressed mineral wool bat pieces. Will cover in breathable fabric. Will sit across the corners of front of room so there will be an air gap behind them.

In looking at a thread over at Gear Slutz it was suggested using a basic simple reflective material of some sort like brown kraft paper or brown drop cloth paper or plastic dropcloth over the batting and under the Fabric Material covering the traps.
Glen from GIK also chimed in as did others about adding some diffusion of some sort. Glen suggested slats (I guess something in the vein of their scatterplate). Others then talked about the BAD scatterplate design.

The GEar Slutz thread is short. One guy said use any random pattern for 1D diffusion of slats.
https://www.gearslutz.com/board/studio-building-acoustics/469204-frk.html

It did link to another thread that was quite sophisticated about the detailed BAD holed panel design or using random generated sequence for random wood slats.
https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/395773-diy-binary-amplitude-diffuser-anyone.html#post6890286

K
My question is this- Is it of value to add some array of 1/8"thick long hardwood slats down the front under the fabric in some sort of random pattern of varying open and covered areas for 1D diffusion?
I don't have the patience or tools to do the full BAD panel with specifically placed hundreds of 1/2" holes over the face of the unit.

Thanks in advance. I am not a hardcore acoustic analytic person- just looking for a simple approach to get some basics here.
The Bass Traps are a no brainer. Adding some brown paper or thin plastic cover over the batting would be easy, of course.
If adding some array of wood slats would enhance the unit overall effectiveness that would be a bonus.

« Last Edit: 5 Oct 2020, 08:57 am by Lkdog »

JLM

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Re: DIY Bass Traps and membrane or diffusion of some sort?
« Reply #1 on: 5 Oct 2020, 11:52 am »
What problems are you trying to solve?

Random slats (your second link) are a diffusion device, only limited effectiveness at higher frequencies.  Diffusion treatment is based on the laws of physics and the size of sound waves versus half the the crevice depth, so are typically limited to 1,000 Hz and higher (about 6 inch depth).  Wideband diffusion requires a good variety of varying depths, ideally oriented in both horizontal and vertical planes.  Here's a good DIY example of what that link is trying to explain:  prerecords.com/Diffusor.cfm

Going for bass absorption, it's essential to use effective materials.  Owens Corning 703 high density fiberglass is the gold standard, Roxul is reportedly a second option, but all else (like mineral wool) is a crap shoot.  Look at the lab testing numbers, can't go by instinct or appearances.  I own GIK 244 panels, both the "full range" and "range limiter".  Without taking them apart the only difference I can find is that the "range limiter" panels have a solid panel (masonite?) on the front.  Masonite would be much more effective than paper.  The concept is to reflect sound that is "trapped" in the media for a second absorption. 

Lkdog

Re: DIY Bass Traps and membrane or diffusion of some sort?
« Reply #2 on: 5 Oct 2020, 05:56 pm »
JLM-

Thanks as always for your insights.
Using 6" of high quality Owens Corning mineral wool batting. It matches up with the Roxul and Manville stuff.
Got the frames mostly built last night.

Goal is to start with the basics of Room TX to enhance the sound quality and the room needs Bass Trapping in corners and absorption at first reflections.
I think I may go with a very basic front panel of some sort on the Bass Traps to start.
Right now only using 2" thick ATS Acoustic 2'x4' panels in front corners.
I can switch those to use for first reflections.

Mike-48

Re: DIY Bass Traps and membrane or diffusion of some sort?
« Reply #3 on: 5 Oct 2020, 06:09 pm »
You might benefit from watching some of the videos by Jesco Lohan, a German acoustician and studio designer who uses the name "Acoustics Insider."

I find his videos and other materials really informative. He is not selling products, so he has no dog in the race.

Here is a video on bass traps.

Though his videos are aimed at playback studios for mastering or recording, it's easy enough to take what you want from them while thinking about what might not be entirely true for you. (For example, I like my listening room to sound close to a mastering environment -- quiet and revealing -- but many audiophiles prefer a little more room reverb. What that means is a little less damping.)

Hope that's helpful!

jriggy

Re: DIY Bass Traps and membrane or diffusion of some sort?
« Reply #4 on: 5 Oct 2020, 07:16 pm »

 I own GIK 244 panels, both the "full range" and "range limiter".  Without taking them apart the only difference I can find is that the "range limiter" panels have a solid panel (masonite?) on the front. 


It’s actually a piece of mass loaded rubber or vinyl. I opened up and removed the range limiter from a panel just a few weeks ago, although the panel is 5+ years old, so maybe GIK use something different now. But I pulled it out, rolled it up and put it away for another day...

Lkdog

Re: DIY Bass Traps and membrane or diffusion of some sort?
« Reply #5 on: 5 Oct 2020, 08:47 pm »
You might benefit from watching some of the videos by Jesco Lohan, a German acoustician and studio designer who uses the name "Acoustics Insider."

I find his videos and other materials really informative. He is not selling products, so he has no dog in the race.

Here is a video on bass traps.

Though his videos are aimed at playback studios for mastering or recording, it's easy enough to take what you want from them while thinking about what might not be entirely true for you. (For example, I like my listening room to sound close to a mastering environment -- quiet and revealing -- but many audiophiles prefer a little more room reverb. What that means is a little less damping.)

Hope that's helpful!

Thank you. The video was really good. I think I am on the right track with the build.
« Last Edit: 6 Oct 2020, 03:48 am by Lkdog »