How to make Binary Amplitude Diffusers without a CNC

Short answer: drill a ton of holes.
The holes size, number of holes and sequence are what defines a true binary amplitude diffuser. But if all you really want is a simple perforated panel to provide some hard surface in front of a broadband absorber that looks neat, this is for you.
I started on one end of the panel and just randomly drew a sequence that was mirrored on the other end. For example the sequence for the first line is:
11100110101110101100111
the next is:
01101111010001011110110
and so on. Each is a palindrome, the same from both ends, so really you are just making the pattern on 1/4 of the panel. Very much like making a paper snowflake by folding the sheet twice and cutting the pattern.
My mistake was not making a master template panel to begin with that was accurately laid out and drilled with 1/8" pilot holes. I could then use that panel to layout the other 5 drilling the pilot holes through those to begin with before drilling the 3/4" holes. My final results would have been more accurate and I think I would have saved time overall.
These panels go on the front of broadband absorber panels and stop some of the higher frequency sound from being absorbed. Rooms with too much absorption can sound "dead", and this can fix that while still absorbing the lower frequency content. Most of the lower frequency sound just passes right through these panels and into the trap behind.
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[@IBuildIt]

Short answer: drill a ton of holes. The holes size, number of holes and sequence are what defines a true binary amplitude diffuser. But if all you really want is a simple perforated panel to provide some hard surface in front of a broadband absorber that looks neat, this is for you. I started on one end of the panel and just randomly drew a sequence that was mirrored on the other end. For example the sequence for the first line is: 11100110101110101100111 the next is: 01101111010001011110110 and so on. Each is a palindrome, the same from both ends, so really you are just making the pattern on 1/4 of the panel. Very much like making a paper snowflake by folding the sheet twice and cutting the pattern. My mistake was not making a master template panel to begin with that was accurately laid out and drilled with 1/8" pilot holes. I could then use that panel to layout the other 5 drilling the pilot holes through those to begin with before drilling the 3/4" holes. My final results would have been more accurate and I think I would have saved time overall. These panels go on the front of broadband absorber panels and stop some of the higher frequency sound from being absorbed. Rooms with too much absorption can sound "dead", and this can fix that while still absorbing the lower frequency content. Most of the lower frequency sound just passes right through these panels and into the trap behind.

[@kynyc1]

You have a bass trap with some reflection. To provide diffusion over a range of frequencies the math matters. So it's weird that the title is diffusers that you ignore the actual diffusion.

[@christianjacquet4095]

Bonjour , ancien tuto , mais j' essaye !!! Je comprend pas pourquoi faire des trous , il reste beaucoup du panneau qui va diffuser et peu de place par les trous pour l'absorption !!! Un tissus acoustique doit être bien plus efficace ... non ? Peut être même faire des panneaux moins grands pour le même résultat ... ? Désolé je parle pas anglais et essaye de comprendre en regardant les commentaires , mais n'ai pas trouvé de réponse au pourquoi du comment ! Merci .

[@Traqr]

​@@christianjacquet4095If you look at the room measurements, you'll see that the bass is ringing longer in this room than the higher frequencies. The goal is to balance the sound better, meaning you need a treatment that absorbs bass energy while scattering shorter wavelengths - diffusion is about keeping the sound energy without creating coherent reflections that cause comb filtering and other negative side effects. Simple cloth facing will absorb more of the higher frequencies that are already well managed. This causes the dense "old library" kind of room sound. A carefully perforated panel acts like a single large damper when wavelengths are very long (bass waves), but more like an orange-peel reflector as the wavelengths get shorter. The hole sizes, panel properties, and pattern control how the system manages sound.

[@Wordsnwood]

I just clicked because it was a beautifully intriguing thumbnail... 👍

[@IBuildIt]

Thanks :)

[@wolfgollnitz899]

Yip, same here

[@BillHantzopoulos]

Wow! Incredible patience. Good for you John.

[@IBuildIt]

Thanks 👍

[@_NatBailey_]

Nice job - always great to see people spread awareness about acoustics. At 2:13, In regards to creating an actual BAD panel, if you follow the sequence you optimise absorption at a given frequency range (spacing between holes and hole width/depth are tuned to work at a certain bandwidth). This will likely have more of an overall effect on the phase diffusion you'd get from a BAD than absorption coefficient.

[@rchavez5056]

John you have the patience of a Saint. That's a crap load of holes. Great job.

[@michaeltablet8577]

That's a lot of drilling! Looking forward to the end product. I bet it really helps the room.

[@swaffy101]

Simply amazing! Great work as always.

[@luiscinacio]

Huge work, John. Excellent. Regards from Portugal

[@GregsGarage]

I love the look of the panels!

[@mmmmmmm8706]

Great result, really impressive design you came up with. Would love to hear more about how you came up with the pattern, whether sketchup helped there, or how you iterated to the final design. Gotta be proud of that!

[@horatioswrld]

I only now noticed this is an Audiophile channel and I FREAKING LOVE IT!!! I agree, woodworking is dead (not dead just too many doing it) and seeing what one can do with woodworking skills is so much better! LOVE IT!!!

[@sameoldmphymel]

Holy cow I converted that pattern of holes to ASCII text and it says "Matthias is King"

[@MandoFettOG]

🤣🤣🤣🤣🤣

[@inthefade]

I converted it to Unicode and it says "Help! I'm stuck behind these acoustic diffusers!"

[@gregmize01]

YOU JUST BROKE THE INTERNET GOOD SIR!

[@draztiqmeshaz6226]

Thanks for answering my questions, incidentally or otherwise! That's looking like it's gonna sound as good as it looks, really great! I hope it's ok that I've selected you as my discipline sensei. I'd have a lot more projects done if I could hold my attention to the robotic parts for longer. Cheers!

[@negotiableaffections]

1980's and I dipped a toe into high fidelity listening. A glass turntable mat, all the jiggery-pokery setting up the tone arm. Setting up a listening triangle to maximise bass to treble response and of course shopping to buy the best cost/fidelity I could afford. Found myself listening to the surface of the vinyl groove rather than the music! I suppose these days with all the digital stuff it makes fidelity more of an issue, but HEY! I'm sixty, just hearing the tunes I love is enough. But, shit! I'd love to hear your room when its finished!

[@vicmiramontes5403]

Another amazing project.

[@peterjames2580]

I've always call it "split the difference" Thanks for the Video.

[@TommieG63]

That looks so cool!!!!

[@Wolfdings]

I really love the outcome! I'll definitely put something like this to my music room! Thanks! One advice tho for the absorption material: If you're using rockwool or similar, pack it airtight in large garbage bags and wrap them with some tape. For the low frequency energies these plastic bags have no impact, but you ensure to not having any fibers flying around eventually. I did this to 5 cubic meters in my acoustic ceiling :)

[@lassalade]

the pilot hole trick is gold.. way more precise..

[@michaelm9871]

Been watching your woodworking videos forever. I was not aware you were also into audio. I wonder how many of us are also into audio.

[@nattyphysicist]

I built a theatre room with this idea but could not decide on the covering. This helps, thanks!

[@donaldmumaw]

Excellent video John!

[@IBuildIt]

Thanks :)

[@clintbartenstein6876]

It has a really cool look to it! I am not familiar with how this will help the sound but hope it helps because that looked like a ton of work

[@TurboLoveTrain]

I love that Chipotle has these installed on their walls in most restaurants and most people think it's a decoration.

[@davedarling6512]

I wish that more commercial spaces made efforts to make their spaces sound nicer. There are some local restaurants and other spaces that I would love to provide some acoustic treatments to.

[@asailijhijr]

John: It doesn't matter because you can't see it. Us: But the sound can see it!

[@BrentDarlington]

Looks great. It seems like all diffusers are a ton of work

[@jaydee9953]

thumbs up just for the effort...dont even care if it works.....it just looks great!!!!

[@hernangarciamonteavaro]

Great job! Congrats

[@dijpdepijp2154]

Very nice, I love it

[@iwantosavemoney]

This is so awesome I have to say.

[@pauljohn5584]

Man… absolutely beautiful job. Craftsmanship is unreal. I just do not see the point in going thru all this trouble to do it right… and then throw caution to the wind with the math of the hole spacing. You are clearly a skilled woodworker- would it not bother you to see a KZbin video of someone doing something VERY wrong in terms of woodworking? I mean, it’s beautiful yes- but that’s all it is. It’s not predictable in its reflective/absorptive behavior so you can’t know if things are better or just.. different. If all you want is a perforated surface- just use peg board and save the time. But such a good job on execution. especially without CNC machine. Looks great. I cross my fingers for you that it helps your room handle pressure and level better.

[@IBuildIt]

The proof is in the pudding, guy. If the hole math made that much difference, my measurements and listening would have shown that. For your information the point of the math is to prevent just one possible problem: specular reflections. And the plain old walls that 99.999% of people listen in are nothing but specular reflections. So lay of the drama and learn what's important. And I see guys doing woodworking "wrong" all the time. Until they ask me my opinion, I keep my mouth shut. It's none of my business, even though I do have a lot of knowledge and expertise to back up views.

[@inthefade]

This is a cool idea. I'm building a rehearsal space / demo recording studio with my band and looking for sound treatment ideas. Bass traps are important because we're something like a rock band with electronic beats (70s/80s post-punk kinda stuff), but it would be nice to build diffusers like this... I just need to find a friend who has a plywood CNC, or make a simpler pattern I can cut with a jigsaw (like you said, there are only diminishing returns to do it in a specific pattern).

[@3D_Blu-ray_Bunker]

Awesome work, fantastic video. Now they know how many holes it takes to fill the Albert Hall...

[@tjacksonwoodworker3726]

A very cool look..reminds me of the punch cards from the 60s.

[@MerwinMusic]

Awesome!

[@cillyede]

Sehr gut, dankeschön! 🇩🇪

[@drgopta2180]

Props to that drill and your hand haha. CHeers.

[@cynickicksass]

Nice! Thank you!

[@tollakf]

Hi John! Amazing videos! I've just finished drilling 8 BAD panels, 4 sq metres with 2x2" skyline, and 30 sq metres of qrd. And NOW I found your channel... I guess we have some patience in common 😂😂

[@delvalle9256]

Hi, is there any resources in the internet on how to make a template for a particular size ie 24 x 48, 24 x 60 and so on. Thanks

[@MrMarkRoads]

The pattern of the holes will be different for what part of the frequency you're trying to defuse. Not only will a random pattern not work as well, you could be defusing the wrong frequencies and making the problem in your particular room worse. When i built my recording studio I did a pink noise test analysis of my room. This gave me a picture I could see with my eyes of what the room looks like for sound. At that point you can start making your plan of how to craft your room. Your walls look cool and I think that's what you were going for. For sound, every little thing matters.

[@dingdong2103]

There are a lot of half truths or plain old wrong information on this channel, which is a shame.

[@peta1001]

You are right...BINARY anything is not related to sound manipulation in any other way than digitizing analog waveform samples. Just stick to any uniform holes distribution with carefully chosen hole-diameters and surface/hole ratio. I wish you could repeat and film the experiment with suggested panel with binary code illustration holes and compare the effects with your initial product.

[@truman4956]

If you had partially drilled a few of the holes, you could have used it for the screws and painted the bottom of the hole black to match. Great work and thanks for sharing

[@mdbohica]

John, 2 things. 1. Love the videos, they're all great! 2. Your Forstner bit hates you.

[@chrismaughan8029]

John ... You say a CNC machine would be faster ... I'd LOVE to see you build a CNC !

[@llee4225]

You can use a peg board as grid drill guide and mark off the pattern.

[@MaucTopa]

I'm here for John's dark humor

[@luigidaniellmusic]

amazing

[@nraynaud]

"The Wiener-Khinchin theorem states that the squared Fourier transform magnitude of a sequence is equal to the Fourier transform of its autocovariance or autocorrelation function. Thus a sequence of reflection coefficients whose autocovariance is a Kronecker delta function will form a good diffuser, because the autospectrum will be uniform." I don't know man.

[@Rich-on6fe]

Sounds reasonable. I think what it amounts to is that your drill bit needs to be good and sharp, and you might want to have the second battery on charge before you begin.

[@normanbott]

And to think I actually understood some of that once ...haven't touched Fourier transforms in decades; can't even find the book.

[@AquaPeet]

I exhaled through my nose so sharply, that a booger shot out.

[@thecarl168]

it is like the turboencabulator explanation

[@cmdreffietrinket]

@@thecarl168 one of the cross-beams has gone askew at the treadle.

[@hagaimann5515]

Looks really cool! I'm planning on hanging 2 birch plywood 1/2 panels CNC curved of just 1/8 in deep. will it reduce echo in a living room with a high ceiling?

[@JamesManCave]

Wow, that's one sharp Forster bit

[@MandoFettOG]

I was just wondering how many bits he went through

[@TheRainHarvester]

@@MandoFettOG I asked elsewhere and he said he sharpened it.

[@edwardprowell3659]

thank - you

[@sgsax]

Binary pattern, huh? Seems like you missed an opportunity to encode a message in there. Or did you... Now I want to run it through a binary/ascii translator to check. Thanks for sharing!

[@rebbel67]

If a plank falls in that room, and John's there to hear it, will it make a different sound to him than it would to a commenter who's gonna say that the blow-out after drilling the holes in the boards will affect the listening experience?

[@vileguile4]

And here i thought Ron Paulk was crazy drilling all those holes for his workbenches..

[@Jules_73]

It made me crazy after building his bench. I’m still seeing crosseyed! 🤣

[@RambozoClown]

I expected "water based polyurethane", but I wasn't sure how you were going to integrate "polyurethane construction adhesive". You did not disappoint. Are you going to do a back to back comparison with 1mm larger holes? 1mm smaller? ;)

[@PandorasFolly]

I wonder if different types of wood finishes could affect the noise? For example a hard artificial shell like finish vs some oil that leaves the wood exposed

[@CrimeVid]

Backer board, ask your timber merchant to save a couple of cover boards for you, it’s usually rough 3/4” MDF here, (I’ve used them for all sorts)

[@mckenziekeith7434]

How does paulk drill those 20mm holes in his workbenches. I think he uses some kind of guide. Not sure if that would work here.

[@srupp9271]

Man that's a lot of work but nicely done! Now I guess that you did your research before you built these. And when I look at it a slat diffuser would be a lot simpler to build. Is there a significant advantage of using these over a slat diffuser? My only guess would be that these absorbers a lot less high and mid frequency? And do you have a west with a calculator that you could reccomend?

[@KarissaBoBissa]

How many charged batteries did you go through on the drill gun?

[@afriedli]

Wow! I would have seriously considered using laser cut MDF. Certainly worth pricing it up and weighing the money cost against the value of your time.

[@cliveclapham6451]

Holey John holey looks good to me😉😎👍

[@DrinksInHighPlaces]

Will the sound be scared of the wrinkles in the fabric?

[@TheRainHarvester]

I understand your predrill recommendation, but just curious why, at the beginning of the video, did you use the forstner bit to only drill a mm for each hole. (Was it to keep your bit sharp during initial drilling of each hole?)

[@IBuildIt]

Exactly - that was my thinking, to keep the bit sharp long enough to cleanly drill the start of each hole, then hog out the rest after it gets dull. I quickly abandoned that idea, though.

[@TheRainHarvester]

@@IBuildIt Thanks! Is it easier to sharpen the bit? Or do they ever return to their original sharpness?

[@IBuildIt]

I made a video on my main channel on sharpening forstner bits a few years ago. I sharpened this one at least 6 times while drilling the nearly 4000 holes.

[@MandoFettOG]

@@IBuildIt how many battery charges did you go through?

[@IBuildIt]

Surprisingly few, but these are the big 60V ones.

[@RBallarddesigns]

Neat project John. Looks like Morris Code

[@3maisons]

Is that a combination of Morse Code and Morris Dancing?

[@RBallarddesigns]

@@3maisons it’s a case of fat thumbs, autocorrect, and not looking. Hahaha

[@3maisons]

@@RBallarddesigns I thought you made a pretty good pun; I guess it was accidental.

[@Cannybiz]

Wow

[@trainsplanes6517]

So a 30 Hz tone has a wavelength of 30 ft; what do a bunch of 1 inch holes do?

[@latifmunjaini3243]

what size of plywood do you use?

[@williamtomkiel8215]

How would I know if my HT needed this?

[@wemel007]

Hey John, don't you have the equipment to measure sound reflection? I would suggest a small-scale experiment to measure if the random pattern differs in absorption / reflection characteristics from the special pattern you spoke about. Although it might be challenging to measure bass absorption on a smaller sized panel

[@IBuildIt]

My ears :) I'm making room measurements using REW in ten locations throughout the room as I progress through the build. Mostly concentrating on reverb time in the lower frequencies to get those down without killing the high end in the room.

[@r.b.fraunhofer1655]

This can a lot of work for a home studio. You can see the procedure in the book Acoustic Absorbers and Diffusers, Peter D'Antonio and Trevor Cox. You will get diffusion from an arbitrary pattern, just not as uniform as the BAD design.

[@JOSEPH-vs2gc]

One of those times an Audio Book or a Podcast series is worth listening to as you drill all those holes... what did you listen to john?

[@garywilkinson8605]

super cool but how do I get your manuals? Your link basically links to more links and so on. Seems like it would be nice to just buy a pdf of it. You about lost me on this.

[@ryanshoemaker]

You will be recreating the Maxell "blown away" picture when this room is complete, right?

[@IBuildIt]

I'd need a pair of L100's

[@todd_halfacre]

This might be silly, but I have to ask as I’m very interested in this Could you use a pegboard panel for your initial layout panel as far as the 1/8” pre drill layout? I started this vid and looked over at some random pegboard in my shop and thought, hey......

[@IBuildIt]

As long as the pegboard hole spacing is what you want, sure.

[@yzmoto80]

“And to fasten that, I’m using polyurethane construction adhesive, because it’s polyurethane construction adhesive compatible, and it’s most in line with the polyurethane construction adhesive compatible type projects, that I usually use polyurethane construction adhesive on. 😎

[@wingnutbert9685]

I know this is an older vid, but could you not do as you said and grid the first panel, drill your pilots, use that panel as a pilot drilling template for each panel. But instead of using a backer board that gets chewed up and gradually less effective, why not use the next panel as the backer for successive panels. Requires good panel to panel alignment, of course. But starts the holes in the next panel and might help with tear-out too. Just a thought. :)

[@frankrizzo7781]

A big hole saw and fewer holes works well. Sound being not to intelligent goes into larger holes even if there are fewer of them.

[@drivingmenots]

So my question is: is this a listening room, or a performance room, or a combination? You may have answered that already, but I have no idea where.

[@JimDockrellWatertone]

Holey holes Batman!

[@IBuildIt]

Hold the whole holes, Robin!

[@mediocreman2]

Well does this accomplish?

[@heyimamaker]

Is the idea of a bass trap to prevent the walls from vibrating and feeding other frequencies back into the room?

[@IBuildIt]

Your comment inspired me to make a video talking about bass traps and what they do, and that'll be out later today.

[@heyimamaker]

@@IBuildIt I look forward to it!

[@Welshcampercreations]

What are you doing with your basement. New workspace

[@scottspropertyservices6877]

So if you drill these holes into ply it makes it a binary patterned sheet. Does that make a standard ply sheet non-binary?

[@nelsondbarrera4697]

hi! what is the mathematical sequence to draw the holes in the wood, thanks

[@LeonPhythian69]

I too would like to find some sequence documentation, if you managed to find a link to any in the last 8 months can you post a link to any?

[@ratherbecampin]

I would love to see a full detail build of this room as it goes. Also a question if you find time to answer. What will be the first thing you listen to when the room is finished??

[@IBuildIt]

More coming, for sure.

[@extramedium3920]

Just doing some quick calcs here, I am thinking that driling out a 4x8 ply would take about 90 min. ea. on avg.

[@extramedium3920]

so basically a full day of drilling to do a 20ft wall. hmm. I might have to rethink this.

[@strandedpirate6346]

Watched and I still don't know what you're making or why.

[@PeterBestel]

Man, that's a mind numbing amount of drilling. QRDs for the centre?

[@IBuildIt]

Unfortunately, the room must have a TV screen (monitor) so that will be on that front wall with a quadratic diffuser on each side to fill the space. You can actually see some of one of those diffusers in the picture of the wall in the video.

[@jrmintz1]

How are you making the decisions about acoustics? Are you working from a book or using software?

[@IBuildIt]

Past experience and online research, mainly. It's time consuming because there's a lot of less than accurate information floating around and then you only recognize it as inaccurate after you've learned quite a lot. The basics are: the lower the frequency, the harder it will be to treat and to effectively treat it requires space. 2" of foam glued onto the walls won't do much, in other words.

[@jrmintz1]

@@IBuildIt Yes, I know some of the recording studios I work in have bass traps that are three feet thick, depending on the frequencies they're trying to absorb. The best of the guys who design those spaces make a lot of money, and for an engineer the great sounding rooms are worth every penny!

[@bazwillrun]

I have the time...I dont have the patience !...if i was that bothered about audio quality I'd buy them...

[@dilbyjones]

How does this actually work?

[@josheppley2767]

John, could you have gotten away with a thinner plywood?

[@IBuildIt]

Yes, or even use MDF instead.

[@Yonatan24]

Could you have used foam instead? Insulation foam, if it exists? To save a ton of time drilling.

[@IBuildIt]

Foam absorbs sound, it doesn't reflect.

[@Yonatan24]

@@IBuildIt I thought you wanted it to absorb sound. How does reflecting the sound back help?

[@IBuildIt]

Sound is made up of different frequencies. So you don't want over-absorb some, like higher frequencies, while trying to absorb the lower frequencies. Lower frequencies are much harder to absorb because the waves are much longer and they have more energy. Notice how you can hear bass thumping in another room, but you can't hear much high frequency stuff? Bass is very difficult to absorb and you need a lot of treatment to do it.

[@carenclemmons5002]

@@IBuildIt nice explanation. Thx. Still is there anything as sweet as the pre-digital sound? Me thinks not so much. I’d bet the sound in your room gets the sound way closer to that sweetest sound. Good work. Amazing focus and execution.

[@Simjedi]

Time to invest in a CNC machine for this type of project....lol

[@andonizulaikaerrasti6525]

Curioso

[@arlenesauder1913]

You could’ve stacked three panels at a time drilling

[@kennethnielsen3864]

60ed.

[@nils1953]

Audiophiles are funny. I look at this and think it's completely overkill for anything I could ever listen to. Then there are people looking at this and thinking, it doesn't have the right sequence and it's not good enough.

[@ryanmccue8180]

I think audiophiles are full of shit I've worked on studios in la they think they know so much lol "Professing themselves wise they became fools"

[@vicoilsteems9764]

Still dont understand what you are doing and why, what are you going to make your basement sound better for are you making theater room, a band practice space, recording studio ?

[@sarreqteryx]

that's not OSB, it's plywood.