It looks magnificent! Congrats! Great effort!
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3D printing a QRD N53 diffuser
- Thread starter kemmler3D
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kemmler3D
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- #83
Thanks for saying so, much appreciated.
The best news is my wife has deemed it "not as bad as she thought" so it doesn't have to go straight onto craigslist.
I will need to enlist help to hang it properly... right now it's just sitting on top of a cabinet.
theREALdotnet
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Which spot are you planning on treating with the diffuser, the front wall?
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kemmler3D
Master Contributor
- Thread Starter
- #85
For QRDs the distance needs to be 3x the minimum design wavelength, which limits me to the back wall (behind the LP).
I am using it for an office nearfield setup where I sit very close to the front wall. I plan on treating the front wall (and maybe ceiling) with BAD panels at some point in the future...
Cool project! Reminds me of these:
www.acousticmanufacture.com.pl
www.acousticmanufacture.com.pl
Skyscraper 101/101 - acoustic manufacture
www.acousticmanufacture.com.pl
Dyfuzor Skyscraper 73/183 wood - acoustic manufacture
www.acousticmanufacture.com.pl
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kemmler3D
Master Contributor
- Thread Starter
- #87
Totally, it's the same concept / design but probably with a different process of building it. I wonder how much they cost... the wood one is 300Kg LOLCool project! Reminds me of these:
Skyscraper 101/101 - acoustic manufacture
Dyfuzor Skyscraper 73/183 wood - acoustic manufacture
The plastic one is not really large enough according to the theory. It's said that wells smaller than 2.5cm x 2.5cm will cause loss of high frequencies... the 101 unit is only 1cm per well.
Of course a 2.5m x 2.5m panel is not practical in any sense. Which is probably why you don't see them very often. It would be an interesting challenge to build one, but I think it would need to be assembled in sections and hang from a cabinet rail and would have to ship in several pieces...
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Why? High freq require smaller wells. I guess there is a practical limit on well depth to well area.
Famous Blackbird Studio C is a nice example (not very practical nor affordable though). Ceiling panels are partially with additional high freq diffuser.
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kemmler3D
Master Contributor
- Thread Starter
- #89
According to the Cox / D’Antonio book wells with width of less than ~2.5cm suffer from viscous losses which tends to affect high frequencies the most. I think this could be desirable in some rooms, but then you have a less predictable mix of diffusion / absorption... I think above that width you simply get diffusion without significant absoprtion. The measurements in my room seem to show that, roughly.
However, I think that recommendation is for wells with fins, I imagine it's less of a problem for open wells like the diffuser I made.
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kemmler3D
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- #91
I have some measurements that are almost ready to share, but I haven't had a chance to record the "after" pseudo-binaural audio - things are busy around here, but I haven't forgotten! 
Overall I think it makes a subtle but good audible difference, but so far that's just subjective claptrap of course...
It is more or less in place though - I say "more or less" because it's just sitting on top of the cabinet, I need to enlist a sturdy friend to help attach it to the wall properly. Definitely a "measure twice" situation.
I have no idea how people install things like this made of wood. 300 kilos... do you need a forklift to install it?
Overall I think it makes a subtle but good audible difference, but so far that's just subjective claptrap of course...
It is more or less in place though - I say "more or less" because it's just sitting on top of the cabinet, I need to enlist a sturdy friend to help attach it to the wall properly. Definitely a "measure twice" situation.
I have no idea how people install things like this made of wood. 300 kilos... do you need a forklift to install it?
Hey, amazing job! Do you have any news regarding the measurements? I had exactly the same idea, I already did some test prints on my P1S and I just stumbled upon this forum. I'm currently waiting for the delivery of filament, I'll be using rapid PETG instead, since it's cheaper than high speed PLA and acoustically, it should be almost the same. I do have some concerns regarding layer thickness and sound reflectivity, I spoke with one guy who does designs acoustics for big studios, but unfortunately, he wasn't able to help me. I'm sure that your measurements and insight of what to do differently next time would help tremendously.
Thanks!
Thanks!
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kemmler3D
Master Contributor
- Thread Starter
- #94
Yo, thanks for the message and welcome to ASR!
I have not had a chance to actually do the binaural recording of the "after" yet, but I should just post the before / after MDAT so people can have a look, I guess.
Long story short you don't see much change in FR or even overall decay time, but the CSD looks smoother. Subjectively I would not say that putting up one diffuser was night-and-day but I think it helped. My room still needs some absorption.
Overall I do not think the density of the print actually matters that much... the measurements show very little absorption, and so I think I have to assume that the plastic is reflecting the sound about as well as it's expected to.
My big advice on printing something large like this is to use 5KG rolls... I got mine from Sunlu and it worked out to about $11 per KG.
I will also say, design yours with hanging in mind. I added screw holes to attach a metal cleat after printing. However, it turns out the infill is too weak to secure the cylindrical screw-holding part inside the print, and it's definitely too weak to hold the entire weight of the diffuser, so I'm going to have to print some cleats and glue them to the back. Currently it is actually still sitting on top of the cabinet in the photo.
If I were going to do it again, here's what I'd do differently in the design:
1. Add more handles for carrying the thing, two was good but 4 would have been better.
2. Add a cut-out for a french cleat on the back, (i.e. top part of cleat is part of the model) also print the cleat to attach to the wall separately
3. Join pieces using dowels, NOT tabs, can print dowels easily
4. When gluing up, don't use thin boards, use 2x4s, the common boards bent and threw off the glue-up a little.
5. Make sure that adjacent / diagonally arranged columns are merged - the slicer adds a tiny gap by default, but the print would be much stronger if the columns were fused. So I would play with the slicer settings to make sure the columns are attached together.
6. I would (if I could) assemble the diffuser in the room where it was meant to be placed. 30KG+ in this large, awkward shape is not easy to move by yourself.
7. Use a normal spool holder, not rollers, the P1S pulls the roll off the rollers all the time and ruins prints that way
8. I would use an epoxy with a working time longer than 5 minutes. I used that one because it dries clear, but it was really hard to work fast enough.
Lastly, I would say that if you're interested in pure performance rather than the aesthetics of a QRD, you are better off building a BAD diffuser. Cheaper, easier, more effective per unit of area.
Definitely keep us posted on progress if you end up building one! Happy to answer any other questions.
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I would like to spend the time incorporating this into a design, I know you detailed how you got to where you were but would you mind sharing your stl files? If I could take the time to remix them based on the suggestions you made I think many other DIY audiophiles would benefit.
I also just want to point out this is amazing work!
