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QRD29 Build - Finally! (Read 5229 times)
Lonely Raven
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QRD29 Build - Finally!
12/05/16 at 18:20:26
 
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.





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SonicSeeker
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Re: QRD29 Build - Finally!
Reply #1 - 12/05/16 at 19:33:11
 
Nice job
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litefootdan
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Re: QRD29 Build - Finally!
Reply #2 - 12/06/16 at 03:56:19
 
Wow!  Your work looks really, really nice.  It is quite an inspiration.  

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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #3 - 12/06/16 at 08:16:54
 

Thank you both. I have quite a ways to go before *I'm* happy.  So I'm definitely going to sharpen my skills on smaller ones while perfecting the QRD29.

Hell, I tried 6 different glues on the big QRD29 diffusers till I found one I kinda liked. I'm still not 100% happy with how the glue sets up, or how difficult it is to evenly lay out these 48" pieces evenly with the adhesive fighting me the whole time.

I'll figure it out...or I'll just come up with a different method of building them.
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #4 - 12/16/16 at 21:15:55
 
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. Smiley  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)






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« Last Edit: 12/16/16 at 21:16:22 by Lonely Raven »  
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Re: QRD29 Build - Finally!
Reply #5 - 12/28/16 at 01:02:35
 
DAMN, LR!! I haven't been on the forum for a few days, but that's a SERIOUSLY good-looking saw. Even I might be able to cut a straight line with that.
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #6 - 12/28/16 at 07:54:37
 

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.   Grin
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Re: QRD29 Build - Finally!
Reply #7 - 12/28/16 at 15:44:12
 
Looking good.  I like those angle cuts!

Here is a shot of my el presidente inspired QRD 23 via the foam method.



I ended up putting these on the side and reshuffled the front of the room to be inverted fractal, QRD7, QRD13, horizontal QRD13, QRD13, QRD7, inverted fractal.




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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #8 - 12/28/16 at 16:35:06
 
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!
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Re: QRD29 Build - Finally!
Reply #9 - 12/28/16 at 17:18:35
 
What I'm impressed with is your hole with the recess.  How are you cutting them?  I figure a router with a template but how do you make the template?
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Re: QRD29 Build - Finally!
Reply #10 - 12/28/16 at 19:37:40
 
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.
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #11 - 12/29/16 at 02:03:36
 
Quote:
What I'm impressed with is your hole with the recess.  How are you cutting them?  I figure a router with a template but how do you make the template?


I'd take pictures, but I hurt my neck, so I'm not super mobile right now.

You can get a Jasper circle jig, which I had many years ago, but it didn't go bigger than 15". So I just took some scrap 1/4" MDF from my diffuser builds, and screwed it to the base of my plunge router. From there you just measure from the bit out to half the width of the circle, and drive a small nail through the jig and into your workpiece. Fire up the router and spin it around the nail a couple times.

It helps if you can divide fractions so you can eaily figure out 1/2 of an 18 5/8" circle. Metric would certainly have been so much easier! LOL
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Re: QRD29 Build - Finally!
Reply #12 - 12/29/16 at 03:06:33
 
9.3125 or 9 5/16" for carpenters. I'm a decimal kind of guy myself.
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Archie
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Re: QRD29 Build - Finally!
Reply #13 - 12/29/16 at 16:15:16
 
Quote:
9.3125 or 9 5/16" for carpenters. I'm a decimal kind of guy myself.


I can't seem to find my decimal tape measure!   Undecided
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Archie
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Re: QRD29 Build - Finally!
Reply #14 - 12/29/16 at 16:17:34
 
Quote:
I just took some scrap 1/4" MDF from my diffuser builds, and screwed it to the base of my plunge router. From there you just measure from the bit out to half the width of the circle, and drive a small nail through the jig and into your workpiece. Fire up the router and spin it around the nail a couple times.


Brilliant!  So obvious once I see it!   Wink
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Donnie
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Re: QRD29 Build - Finally!
Reply #15 - 01/02/17 at 17:45:16
 
Do the diffusers have to be vertical? Can I do horizontal?
I have "packaging" issues in my room. Namely a 37.5" (notice the decimal, I'm not a carpenter) ledge that runs on both my front and back walls. My room is semi underground.
Some other issues are going to pop up also.
The main thing is that the room is odd shaped and has a lot of built in cabinetry.
There is nothing like a challenge.
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Archie
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Re: QRD29 Build - Finally!
Reply #16 - 01/02/17 at 18:10:45
 
Quote:
Namely a 37.5" (notice the decimal, I'm not a carpenter)


At least you're not a commie metric system user!   Cheesy
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Re: QRD29 Build - Finally!
Reply #17 - 01/02/17 at 18:11:38
 
I know that ledge well.  Had it in my last house.  You can run them horizontal and/or vertical.   I do both but my primary direction is vertical.

El presidente can speak more knowledgeably about this but i would make some at the 37.5 to run vertical and some to run horizontal on the ledge.  To me they don't shrink the size of the room.  Rather they seem to increase the size from a perception point of view.   So you are really not giving up room.

There is a minimum distance at which they are effective so you'll need to keep that in mind.
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« Last Edit: 01/02/17 at 18:15:37 by Palomino »  

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Donnie
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Re: QRD29 Build - Finally!
Reply #18 - 01/02/17 at 18:29:42
 
Quote:
At least you're not a commie metric system user!

Oops, I meant a 952.5 MM ledge!
25.4 is your friend.
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« Last Edit: 01/02/17 at 18:31:10 by Donnie »  

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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #19 - 01/02/17 at 20:52:45
 
Archie - I realized I took these photos and forgot to post them.

Random hunk of 1/4" (or .25" for Donnie) MDF panel screwed to the router base. I knew my base was painstakingly centered, so I didn't want to remove the base and more easily screw this from the bottom of the router...




Here is the jig from the underside. the bigger circle is where the 1/2" (or .5" for Donnie) spiral router bit (a really beautiful/nasty looking thing) cut through the jig.  Then I draw the line and measure out from the outer edge of the bit to exactly HALF the circle I need cut. You can also see two divots to the left and right of the line where the screws I put through the top of the router base into the MDF poked through and scratched up my baffles. I ground them down with a dremel and went on with life.



The first two pin holes are the outer "ledge" that I cut into the Open Baffle for my Betsys (where the frame ring is screwed to the baffle), and the "cut through" circle of the baffle.

The second three pin holes are the rings I cut for the 18" woofer box. If you look closely the outer most one has the 9 and whatever Donnie said so the big woofer could be flush mounted. The inner pin hole is the "cut through" circle, and the middle one is when I went, "Oh crap, the mounting ring on this subwoofer is *way* wider than my bit!", and I went back to clean up a little bit.  :)

So I basically put a strong nail in the center of where I want my circle to be, pop the nail through the appropriate hole, and spin the router around the nail.

Here is a fancy adjustable one that I was too lazy to build since I really only needed these four holes. And mine was accurate to within a 32nd of a inch.

https://www.youtube.com/watch?v=brq3wtKuv0Q&t=473s


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« Last Edit: 01/02/17 at 20:58:06 by Lonely Raven »  
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #20 - 01/02/17 at 21:02:01
 

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!
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Re: QRD29 Build - Finally!
Reply #21 - 01/02/17 at 23:50:26
 
LR,

Thanks for the pictures and explanation.  Just to clarify, you cut all the way through for the smaller circle last since then the waste piece would be loose, correct?
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #22 - 01/04/17 at 06:41:27
 

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

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Reply #23 - 01/04/17 at 15:28:03
 
I made one of these out of Plexiglas and I can attach i to the base of my router.  Its about 5" by 12" with a larger hole on one end for the router bit to go through.  It doesn't look great, but works pretty well.

Like Raven, I measure the width of the flange, divide by two and drill a hole for a pin in the Plexiglas to that length making sure to include the full width of the bit I intend to use in the measurement.  

I also drill a hole for the pin in the center of the baffle.  

I set the depth of my router to match the height of the flange.  

I then insert the pin in the hole in the baffle, fire up the router and rotate it around to route to the depth of the flange.  

I size the bit for the initial cut to equal the width of the flange making sure I have enough room for the screw holes I will use to attach the driver, but also small enough to for the basket to clear when I insert the driver.

I then subtract the bit width from my initial measurement and repeat the process to cut my inner circle all the way through the depth of the wood.

I think this cost $10 compared to the $50 for the Jasper.  Granted, that one has a hole every circumference you'd ever want to cut.  You could do the same for less with a piece of wood, but I like the smoothness of the plexi and the ability to see through it.
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #24 - 01/04/17 at 17:44:34
 

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.
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Re: QRD29 Build - Finally!
Reply #25 - 02/24/17 at 01:16:20
 
Great job on those diffusors, LR.  Do they work really well?  Just curious how they compare to the AQD diffusors you had from PI audio?  I would think not only the added depth of your diffusors but also wood construction should really help in this case?  
I'd been going back and forth if I should pick up some AQD diffusors or try building my own but with my very limited skill and tools, I probably will just ended up buying instead.  
Well, great work, LR!
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Lonely Raven
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Re: QRD29 Build - Finally!
Reply #26 - 02/24/17 at 21:58:35
 

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)
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Re: QRD29 Build - Finally!
Reply #27 - 02/24/17 at 22:23:50
 
+1 on the PI Audio diffusers.  I liked what I heard when you set them up at Aaron's house.  Not as cost effective or as good as building via the foam method, but a ton less hassle.

BTW, Raven, I don't think we ever compared notes on our builds to come up with a best practices for the foam method.  I'd like to build some more of the QRD23s.

I also didn't keep track of my costs, but I think they were less than $50 each.  I will put together a materials list.

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Donnie
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Re: QRD29 Build - Finally!
Reply #28 - 02/24/17 at 22:41:57
 
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?
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Re: QRD29 Build - Finally!
Reply #29 - 02/24/17 at 23:03:21
 
Might be overkill.  Is that stuff pricey?
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Donnie
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Re: QRD29 Build - Finally!
Reply #30 - 02/24/17 at 23:33:41
 
$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...
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Re: QRD29 Build - Finally!
Reply #31 - 02/25/17 at 22:36:39
 

I've tried the spray can version of this on test pieces and it melted the foam. I'm not sure if the roller version would damage the foam or not. I'm pretty sure it's too think for me to spray without an industrial truck bed liner gun. And honestly, I'm done with rolling paint unless it's something really small. It might still work though, and the added mass is good for the diffuser in general.

Only other concern I have would be about smell. Does the rubber offgass a smell for a while? That drives me nuts...I got a smaller, quieter air compressor a couple months back after selling my overlarge one for more than the quiet, little one cost. I can smell the damn rubber wheels on it from across the house! Bleh.

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