I've been working up to this for a while...trying to be low cost, not make things harder on myself, while still being as broadband of a diffuser as I could build in my little garage shop.

I've *finally* completed my first QRD29 diffuser!

The diffuser a Quadratic Residue Diffuser with 29 wells as the name implies. I went for 1" wells with a maximum of 12" depth. The overall device is 30" across and 48" tall, and weighs in around 100# (and is a pain in the ass to move! LOL).  It should affect sound between about 262Hz and 6880Hz.

I'm not 100% happy with the build quality. Keeping the device as light as I could I used 1/8" MDF "fins", which can shift and bow a little. Carrying the big box from the garage shop up stairs to the listening rooms I've knocked a few of the wells a little crooked. I'm working on ways to build these faster, and more accurately with less bow or wells shifting. Overall I'm pretty happy with my first completed QRD29.  After this, I could churn out QRD17 diffusers with ease! LOL I know several people asked if I might have some diffusers for sale soon, and the answer is definitely YES. I'm probably going to be making some easier diffusers that are 6" to 12" deep, and around 24" x 24". I already have one prototype done I'm really happy with. Meanwhile I'll keep improving my build quality on the larger, much more complex diffusers.

Checm em out!















And one of my many (many!) prototypes.

Wow!  Your work looks really, really nice.  It is quite an inspiration.  

Damn, are some of those photos not working anymore?

I really need to find a new online gallery. I liked Zenfolio, I'm just tired of paying for features I don't use. I'm not a semi-pro photographer anymore!

So, I've been working on other projects...leaning towards getting my home theater working better. My living room/Home Theater/ Listening room in a *mess*!  And I have some house repairs to do, so I'm pulled away from diffuser building for a bit.

That said, I've sold off my old table saws and finally upgraded to a 3HP Cabinet saw. It was on sale and I got six months same as cash, with only $99 shipping...so it was worth it.  This inspires me and enables me to work on bigger projects easier, as well as with more accuracy.  So I'm going to make a couple subwoofer boxes for my home theater, and I have a couple more advanced sound diffuser designs I'm working on - both for myself, and those that asked if I could build them some.  :)

(switching back to Zenfolio gallery since Facebook gallery is hit or miss)

I'm so very happy with the saw. I finally got to make some cuts on it. I decided to finally build some boxes for these 18" Home Theater drivers I've been sitting on for like 4 years - so I picked up some MDF and just started building a sealed box. I can't believe how easily this 3HP saw cuts through 3/4" MDF! I was going to jigsaw out some fancy bracing for this box, but just for fun (and to play on the Table Saw more) I cut this open bracing and glued and pinned it all in. I was making cuts so accurately, the whole box pretty much press fit together!





I picked up this little Glu-Bot thing for $8 on Amazon. Absolutely amazing how well this work!












After I get this box finished up and thumping in the Home Theater/Listening Room - I plan on building some jigs for the new Table Saw to help me make the diffusers faster and more accurately, then I'll start on my next batch of complex diffusers. I'm planning a "nested" diffuser - where instead of having tons of 1" wide wells, I'm going to do 3" wide wells, and each well bottom will be a 1" deep by 3" wide) micro -diffuser....basically a diffuser within a diffuser. I'm going to see how this extends my diffusion range a bit, and/or maybe makes building larger diffusers more easily.  

Man those look great!

If I can get up the motivation today, I'm going to do some test cuts on the new diffuser for the back of the room. I took measurements, I'm pretty sure I can go 16" deep on this one!

LR, I really like the fence on your saw.  I think you can make very accurate 1/64" adjustments with it.

Archie, I use a homemade circle cutting jig with the router.  You cut the recess first and then adjust the router position and make the through cut.  You can also use a rabbit bit with a bearing. You don't need a template.

9.3125 or 9 5/16" for carpenters. I'm a decimal kind of guy myself.

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Brilliant!  So obvious once I see it!  

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At least you're not a commie metric system user!  

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Oops, I meant a 952.5 MM ledge!
25.4 is your friend.

Donnie

I can help you design some great diffusers - I think I understand your ledge situation as I live in a raised ranch with said ledge.

Why don't you start your own thread here in the Room Treatment section - and lets start with a description and maybe a drawing of your room. Even if it's just a rough sketch on a napkin with dimensions, and a few photos of what we have to work around. Then we'll work from there.

Tom's right about diffusers *not* making the room smaller...you saw how small of a room he works with, and the diffusers make the walls disappear. If you have free reign over your room, we can make some audio magic happen!

Yes exactly. If you cut the inner (through) circle out first, the jig wouldn't have any support anchor to guide it.

Yeah, lining up those tiny holes with the tiny steel nail in my project is challenging with MDF. It's a lot of feel and sliding around till I find it.

I would buy the PI audio ones.  They work very well (though not as well as a real QRD with wells) - and they are cost effective for what you get. I wouldn't hesitate to recommend them.

Only suggestions would have would be to make sure to paint them with a water based paint of your choice. I just used some off the shelf Flat Black wall paint (with integrated primer) from my local hardware store. It's tedious, and you don't want to glop the paint on - so two or more thin coats is needed. This will fill in the pores and make the styrofoam more solid and reflect like wood. This was tested by a guy in a recording studio forum and he swears by layers of good paint measuring as good as solid wood.

Note: DO NOT USE spray paints, as the propellants and evaporative chemicals will melt the styrofoam and turn it to a globby mess. Water based paints only!

Other suggestion would be to build a wood frame around them as they are fragile. I've snapped off so many fins on four of mine, it's not even funny. They are super-glue repaired and I've even used vinyl spackle to fill in dents and divots where I'm missing the pieces that broke off. I recently purchased an HVLP spray gun so I can more quickly stain or paint the diffusers I'm building....as well as re-finish the PI Audio ones I've damaged and repaired. LOL

Actually, now that I'm thinking about it, it wouldn't be too difficult to glue on some of the dense Pink or Blue EPS foam (insulation styro) from your local home improvement store as a "box frame" instead of wood, just to give the soft styro-diffusers a little more projection from clumsy people like me.  :)

Of course if they will be up off the floor, on a wall where nobody can lean on them or bump into them, or cats claw them up or something...then just paint them and pin them to the wall with a drywall screw. (shrug)

I'm thinking about the painting them to seal up the foam. What about that "Miracle Rubber" stuff? That stuff that seals up the screen door on the bottom of the boat.
Do you think that would work?

$15 a pint. Cheap compared to auto paint. I don't know how much coverage you would get with it.
https://www.amazon.com/Flex-Seal-Liquid-Large-Ounce/dp/B019PFO4KM/ref=sr_1_13?ie...