Custom DIY diffuser panels... (later covered with custom absorption panels)

[Sonnie Parker]

I had ordered some smaller diffuser panels from GIK Acoustics, but after a couple of weeks I learned they were backordered from Asia and they were hoping to have them in by the end of April, so I canceled that order. After looking around, I decided I'd just build my own. I'll get much more coverage and spend a lot less money. I took me about 2 hours to build each panel... then I suspect when I finish painting them (prime, fill holes, and two finish coats)... I'll have about 4 hours in each panel.

This is built from a DIY pattern offered here: https://bettersoundproofing.com/diy-sound-diffuser/ ... and ... https://www.diyaudio.com/forums/roo...iy-depot-sound-diffuser-panels-step-step.html

This is a 3’x8’ quadratic13 diffuser that ended up costing me about $300 for both panels, including the paint. Construction uses larger dimension pieces laminated to create the correct well depths which diffuse a wide bandwidth from approximately 400Hz to 8000Hz.

The highlights:

These will be mounted directly behind my MartinLogan 15A speakers in the corner area of each front wall. This area is about 40" wide and the panels are about 34" wide.... the area is 87" high, so they won't be quite 8ft tall (7'3")

Here is a primed unit and one that I have the first finish coat to match the wall finish in my room.

 

[ddude003]

Very nice work @Sonnie... Are we going to get to see a before and after REW scan of your room?

By the way, I have been thinking of building a pair these very same Argen fractal defusers my self...

So, I am very interested in your experience and thoughts about these, coming from an ML ESL enthusiast...

 

[Sonnie Parker]

Very nice work @Sonnie... Are we going to get to see a before and after REW scan of your room?

By the way, I have been thinking of building a pair these very same Argen fractal defusers my self...

So, I am very interested in your experience and thoughts about these, coming from an ML ESL enthusiast...

That would be a good idea. I believe I have some raw measurements already for when I had all the absorption panels in place on the front wall. I'll take some more measurements with the bare wall before I install the diffuser panels. Then of course afterwards as well.

 

[Todd Anderson]

Looking good! How much does it weigh?

 

[Sonnie Parker]

Looking good! How much does it weigh?

Probably around 100lbs or so. It can't be too terribly heavy since I can pick it up and move it around.

 

[Todd Anderson]

I think we need a video...

You picking it up and pressing it over your head.

 

[Sonnie Parker]

Uh ... oh yeah... the part with me falling on the ground and it landing on top of me would be the funniest part.

 

[ddude003]

Hey, @Sonnie don't do that... We want to hear what you think about the diffusers first...

I think your next DIY project would be to build yourself some Klipsch Jubilees...

 

[phillihp23]

This is diffusers on a industrial scale

 

[jmorris644]

I have 6 foot maggies. They are bi-radial like your martin Logans but I never thought of diffusing behind them. Being as I know very little about acoustics these may be really dumb questions but I wish to ask anyway.

Can I ask why you considered this? Will this not send frequencies back toward the listening position? And at different time-based arrivals?

Thanks

 

[Sonnie Parker]

I have 6 foot maggies. They are bi-radial like your martin Logans but I never thought of diffusing behind them. Being as I know very little about acoustics these may be really dumb questions but I wish to ask anyway.

Can I ask why you considered this? Will this not send frequencies back toward the listening position? And at different time-based arrivals?

Thanks

Not dumb questions by any means... thanks for asking. The best answer I can give you right now is that this is what

Floyd Toole recommends it in his Sound Reproduction book for dipole speakers. Furthermore, in the blind testing that Toole elaborates on in his book, more people preferred no side wall treatments. There are other prominent individuals in the industry speaking the same or similar things... that diffusion is better than absorption.

Linkwitz wrote in his theory paper on Room Acoustics:

The wall behind the speakers should be diffusive. The rear radiation from a dipole must not be absorbed or it is no longer a dipole. Similarly, the side walls should not absorb sound at the reflection points but diffuse it.

Here's an interesting article by Keith Yates: https://keithyates.com/a-matter-of-diffusion/

I've always used absorption on my front wall and side walls. I will be doing some measurements with absorption on the front wall, no treatment, then diffusion, to see the measured differences and what the various reflections are doing (hope to accomplish this today). I've listened for years and years with the absorption, so now I will try the diffusion and see if it seems to improve what I hear. I no longer have side wall absorption on the front half of the room... just decorative non-acoustic panels.

 

[VinceHoffman]

Nice work @Sonnie! I think your really gonna' like what this does for the back-wave of your Martin Logans. I would gather this was built based upon Tim Parry's Arqen Leanfusor design? I've read good things about that particular DIY diffusor being both simple to build and effective in use. I was seriously considering a rear wall diffusor DIY project based upon Arquen's Fractal Leanfusor variant until I discovered the cost-effective diffusor products from SevenAudio (in Poland!).

For those of you that would rather have someone else do the work Lukasz at SevenAudio builds the product to order quick but economy shipping over the Xmas holidays was a long wait. Order to arrival here in Canada was about 3 months. I suspect shipping would be quicker at this point.

 

[Sonnie Parker]

Thanks and nice looking room. How much are those panels?

 

[VinceHoffman]

Thanks and nice looking room. How much are those panels?

The five N7x7 fractal 1D units which make up the modulation were under $1500 CAD ($1150-ish USD) shipped and all import costs included. Of note though is the fact that all my units were built in a custom furniture board frame color and that the three central units included much more significant customizations. The center unit is 2" deeper while the flanking pair were 4" deeper than stock and all three were built in a custom height to suit my needs. The resulting air cavity behind each was filled with 2" semi-rigid polyester wool insulation boards. I used a french cleat mounting with all units spaced an inch of the wall. The extruded polystyrene diffusor material becomes acoustically transparent right around the bottom of it's scattering pass-band 400-500Hz. The polyester wool absorbent behind the three deeper hybrid diffusors then offers some some useful mid-range and upper bass absorption to take over below the diffusion.

Lukasz charged very little extra for these changes and was awesome to deal with and very collaborative throughout.The end-result exceeded expectation in all regards except shipping time (which in retrospect really wasn't that surprising either- Doooh!). Lukasz is a packaging super hero. His clever light weight packaging added little to the shipping cost and protected all 5 units perfectly during 2-1/2 months in transit! The product is very high-quality in both appearance and function. Fabricating the diffuser wells from extruded polystyrene rather than the typical expanded polystyrene makes for a far more durable product. Acoustically the end result of replacing my 10 year old 9sq ft DIY 2D diffusor with the 30sq ft of 1D fractal diffuser was jaw dropping. Any stereo recording (played back in stereo using L&R mains and subs) which features a real or synthesized acoustic space now blows past the walls and ceiling and fully occupies the front half of my 20.3x14x11' room.

 

[Sonnie Parker]

Very nice... I'd have to build them though... a bit rich for me.

So I finished and mounted the panels. They ended up being about 71lbs each... not really bad at all, although they felt like 150lbs to me.

 

[pratul]

Eagerly waiting for your before and after tests with this diffuser
All my room treatment efforts are on hold.

 

[pratul]

Very nice... I'd have to build them though... a bit rich for me.

So I finished and mounted the panels. They ended up being about 71lbs each... not really bad at all, although they felt like 150lbs to me.

View attachment 40355 View attachment 40356

Looks really nice! Glad to see a Pink Floyd fan! Must sound amazing on those speakers.

 

[tesseract]

@Sonnie , We discussed this years ago, glad you are getting around to trying it. Hopefully this proves better than simply absorbing/deflecting the backwave. Looking forward to your impressions.

I suspect the elimination of side wall treatments will have a negligible effect on the SS&I, as these are dipoles. Cool Pink Floyd tapestry!

 

[jmorris644]

The wall behind the speakers should be diffusive. The rear radiation from a dipole must not be absorbed or it is no longer a dipole. Similarly, the side walls should not absorb sound at the reflection points but diffuse it.

I loved the article. I have attached a pic of the front of my theater/listening room. I am in the middle of construction.

I have 2 completely separate systems. One for the theater and the other for listening. The maggies are on a hybrid tube system. The screen is acoustically transparent so the false wall that is behind the maggies is currently not treated at all and the sheetrock wall of the room itself is 3 feet behind that one.

Based on the article that you just told me about, at this stage, I plan to build diffusers to go behind the baggies. The side walls are sheetrock with batting behind them. I should leave them as is, correct?

Also, am I thinking correctly in putting diffusers behind the maggies now? I had originally planned on putting absorption panels behind them.

 

[Sonnie Parker]

I have started a new thread with some measurements. I listened for a good bit last night and everything sounds good. I can't say it's any better or worse, still sound very good... lol.

MartinLogan Renaissance 15A Speaker Measurements and Room Influence

We hope to fully review these speakers (MartinLogan Renaissance 15A) at my home during our July GTG (with Wayne and Dennis present). These measurements may be something we use at that time to help with the review. I also have a pair of Revel F328Be speakers, which are considered by many in the...

www.avnirvana.com

I loved the article. I have attached a pic of the front of my theater/listening room. I am in the middle of construction.

I have 2 completely separate systems. One for the theater and the other for listening. The maggies are on a hybrid tube system. The screen is acoustically transparent so the false wall that is behind the maggies is currently not treated at all and the sheetrock wall of the room itself is 3 feet behind that one.

Based on the article that you just told me about, at this stage, I plan to build diffusers to go behind the baggies. The side walls are sheetrock with batting behind them. I should leave them as is, correct?

Also, am I thinking correctly in putting diffusers behind the maggies now? I had originally planned on putting absorption panels behind them.

That is what I would do based on all of the research I've done. If it don't work for you, you can always hang absorption panels on top of the diffuser panels. The side walls really comes down to preference. Some liked absorption, some liked diffusion, but most like nothing.

 

[what bass]

Sonnie, in the O.P., if what I read translated with my limited knowledge holds true, these are prime 13 diffusors?

I'm at a loss as to how you arrive at the need for prime 13? I need a better understanding of diffusors. I've read that the well depth is based on 1/4 wavelength and well width is based on 1/2 wavelength. Ok. Now, how do we get to prime number?
I'm sure there is a thread, article or paper somewhere that explains all this along with a program that calculates order of the well arrangement.
Could you or someone please post a link?

Beautiful room btw

 

[pratul]

Inspired by this post, I started doing some research on diffusers and came across this site. It explains the different types and includes calculators and examples. I actually even bought the book he references but it is too complicated for me to follow.
https://www.subwoofer-builder.com/qrd.htm

 

[Sonnie Parker]

Sonnie, in the O.P., if what I read translated with my limited knowledge holds true, these are prime 13 diffusors?

I'm at a loss as to how you arrive at the need for prime 13? I need a better understanding of diffusors. I've read that the well depth is based on 1/4 wavelength and well width is based on 1/2 wavelength. Ok. Now, how do we get to prime number?
I'm sure there is a thread, article or paper somewhere that explains all this along with a program that calculates order of the well arrangement.
Could you or someone please post a link?

Beautiful room btw

Really... just from reading Toole's book, and several other articles scattered about, which most are linked in post 1 and 11, although there were a couple I did not link that basically repeated a lot of the same information. The reason I chose what I did was to get more consistent and uniform diffusion, rather than random diffusion. I chose these panels because they are large, cover from floor to ceiling, and diffuse the majority of my direct backwave from the speaker. As far as measurements, impulse response, and ETC overlays, it doesn't appear that absorption was doing anything at all vs no treatment, and diffusion is affecting it only slightly, but apparently per the measurements in a slightly good way. I think this has to do with the fact my speakers are pulled a good distance out into the room, and the distance to the primary position is only 2.5 meters from the speakers. I'm certainly not an expert on any of this, so it's a lot of trial and error.

Inspired by this post, I started doing some research on diffusers and came across this site. It explains the different types and includes calculators and examples. I actually even bought the book he references but it is too complicated for me to follow.
https://www.subwoofer-builder.com/qrd.htm

That's Bill Collison... we actually host his website. Smart guy and very informative.

 

[ddude003]

Sonnie, in the O.P., if what I read translated with my limited knowledge holds true, these are prime 13 diffusors?

I'm at a loss as to how you arrive at the need for prime 13? I need a better understanding of diffusors. I've read that the well depth is based on 1/4 wavelength and well width is based on 1/2 wavelength. Ok. Now, how do we get to prime number?
I'm sure there is a thread, article or paper somewhere that explains all this along with a program that calculates order of the well arrangement.
Could you or someone please post a link?

Beautiful room btw

@what bass, You may also want to review the information and design theory behind these types of diffusers at http://arqen.com/sound-diffusers/

 

[NBPK402]

Uh ... oh yeah... the part with me falling on the ground and it landing on top of me would be the funniest part.

Then you would truly be diffused.