D. I. Y. Polys

[mikahanau]

Originally Posted by Glenn Kuras

Pictures??

Sorry Glen
Since my Polys are implented into the wall structure, i will not post pics until i finished the whole room.
I don`t want to show the details behind the fabric to all people, since i work at some complex treatmets, not just some rigid insulation in the corners, and some traps at other surfaces.

You will see pics of the room, when all important things are in place.
cheers
Mika

[johndykstra]

bumping this for opinions on my testing methodology...

[PaulP]

Originally Posted by dykstraster@gmai

bumping this for opinions on my testing methodology...

Without commenting on the methodology I suggest you go ahead and do what
you think makes sense. Then, by doing, you'll get a good idea if it's good or not.

There appears to be very little in the way of testing expertise in this forum,
at least of the kind that would be shared, so you're kind of on your own. Us
others will certainly benefit if you keep us informed on your progress.

Paul P

[johndykstra]

Got 4 more built yesterday, two to go.

Will likely finish them tomorrow, and perhaps do the testing. I would really like to get some feedback, as to whether or not it is paramount to get some impulses along with the null tests. Problem is, I haven't yet mastered REW, and if impulses are crucial, I'll have to wait to do the testing. Can independently created audio, say a machine produced "hand clap" be later analyzied by REW to determine the differences with and without treatment, or can it only analyze tones it produces?

Here's some tips I haven't mentioned until now in regards to construction.

- it's a good idea when screwing in the fasteners to only barely have them make contact with the face, and let the ply adjust slowly to the curvature. Only later should you go back and snug the screws with a manual screw driver.

- we've had far more success with less tiny cracks when we saturate the face of the ply with furniture wax. We've been using this stuff called "cabinet magic", and lay it on thick to a haze... just working it into the surface.

[johndykstra]

Here's some shots from yesterday's progress:

1. waste not want not. I averaged about 3 traps before I had a sufficient amount of scraps to fill a trap.

2. what's rockwool made of anyway? I kept finding tiny little shards of black metal as I carved, then I hit the mother load...

3. here's the 4 fresh ones (we ran out of finish washers)

4. and two propped up roughly in place with their lighting effects. Hey, who left that jar there?

[avare]

In case you have not been told lately, fantastic thread!

Depending on the plant rockwool (actually a trademark, like kleenex, sharpie or big mac) the solid material are various forms of rock, or slag.

Andre

[johndykstra]

Thanks Andre!

Do you have any opinions on my testing plans?

It's likely it will happen tonight, so I'm at the zero hour here for input.

[johndykstra]

Here's a few photos of the testing process. Unfortunately, I neglected to take photos of the "before", however, mics were in the exact same place.

The test.

Well....

The null idea was an utter failure. The two passes I did without the polys, after lining up the di signals on sample level zoom, there was still audible sound. You could hear a VERY thin and digital sounding drum beat. Variations due to the creation of the beat by the drum machine I presume. If I was thinking straight, I would have recorded one pass of the drum machine, and replayed that recording...as it was, I simply replayed the drum machine separately every time...thus the "performance" differences on each take. When attempting to null each individual mic of the no poly tests, not only was there the same difference audible from the di null, but even more so from other little air pressure anomalies... nulling, given my testing methodology, is simply not going to be useful.

I do however, have tracks of before and after that are A/B-able. There is a difference, albeit subtle. These subtle differences on recording are hugely compounded when actually being in the room. I don't want to divulge too much synopsis until after I'm able to get something up here to have everyone draw their own conclusions without any coaxing.

What I can tell you, and isn't possible to reflect in the tracks, is that the room is FAR more even in response from place to place. And not just in high frequencies. We practiced a song or two after getting everything cleaned up, and I felt enveloped in sound. I could hear everyone there far more articulately.

I will be posting some more "money" shots of the room through out the day, as I get some time.

[johndykstra]

I should explain the mounting method. My initial plan was to use "L" brackets attached to the frame and wall. I was planning on securing them to the wall first, get the poly in place, then attach from the top and bottom. As you can see in some pictures, my VERY LOW ceiling height won't allow that to happen.

As an alternative, we simply removed the 4 corner screws from the front plate, and replaced them with 4" screws while the poly was held in place. Normally, with a simple drywall constructed wall, I would be concerned that it would hold. Our walls, however, have 5/8" mdf layer behind the drywall, so there's plenty of "bite" back there to keep these things up.

[johndykstra]

here's more:

[johndykstra]

And some more...

[terry j]

they look very nice indeed.

give yourself a big pat on the back from me yeah??

thanks very much for the thread.

[johndykstra]

Originally Posted by dykstraster@gmai

I do however, have tracks of before and after that are A/B-able. There is a difference, albeit subtle. These subtle differences on recording are hugely compounded when actually being in the room. I don't want to divulge too much synopsis until after I'm able to get something up here to have everyone draw their own conclusions without any coaxing.

update.

I'm growing more and more confident that the introduction of these polys are more significant than I originally stated. I think the problem is, that my control room lacks the ISD to truly hear what is happening after the initial transient. Recordings that have come out of here post poly installation are of a completely different sonic, with a lot less mixing manipulation.

I'm hoping I can track down the original a/b files. Hopefully someone here with a more suitable mixing environment can make better sense of the distinction.

[creativeoutlet]

Hey John, creativeoutlet here. Thanks for the input on the room I'm working on for my son. I am considering a large poly in the back corner of the room. After reading the article by Malcolm that was suggested by Andre, I wanted to run a construction idea past you. In that article, Malcolm suggested that placing them in the corner provided superior results than on the wall, and that hanging them is also valuable as is keeping them as light as possible and open in the back.
I'm considering using a 4' x8' sheet of 1/8th inch plywood. My thought is to screw a piece of aluminum angle, say 1"x1", top to bottom on the two long sides. Then, drill four holes spaced evenly top to bottom in the legs of the two angles that are sticking up from the side attached to the wood. Then, attach the the corresponding holes side to side with cable and a long turnbuckle. Then "simply" tighten the turnbuckles and draw the plywood into an arc. If I understood Malcolm, you only need to draw the edges together 1.5" to get the 6" of arc in the center. If this makes sense, what do you think?
Thanks,
Eric

[johndykstra]

Hey Eric.

The thing is, Glenn is working out a complete room system design for you. To attempt to add or subtract from the design would be foolish without at least some input and go ahead from Glenn.

In terms of your construction method, it certainly seems reasonable. I can tell you that with my build I ran into a lot more problems than I expected... but a decent amount of problem solving abilities should see you through. I like the turn buckle idea.

[tonio]

Great idea. With a turnbuckle you can make an ajustable arc at any time- uh as long as you like getting on a ladder.
Though for a 1/8" luan, you probably won't even need a turnbuckle. You can prolly make a jig for the arc spec or some human help, then just use cable and cable crimps.

[creativeoutlet]

John, you know, that is totally true on the complete room design that Glenn is doing. It is foolish for me, with near zero education on these things, to start meddling with his expertise. Maybe I'll work on the polys for a ceiling to wall application.
Thanks man,
Eric

[creativeoutlet]

John, I spoke to Glenn on that poly idea and he is cool with it. Do you mind if I post my poly building experience on this thread as an addition or should I keep it over on my other thread?
Thanks,
Eric

[johndykstra]

More the merrier. Post away friend.

[RonT]

I don't know exactly what these do....I am sure they do some diffussing but I see that rockwool is added so that makes me think there is some absorption going on as well?

How does these stand up against other forms of diffusers? I am curious becuase I could build these in my sleep and is exactly what I would put in the back of my CR and around my Live Room Walls.

Very well documented and great job. These look kickass! I am down for the Pepsi chanlenge!

How much do you think it would cost for me to build about 30 of them?

[johndykstra]

they provide a good amount of scattering. That's to say, sound that would normally hit it and bounce in one direction is dispersed evenly along the arc. In terms of what it did subjectively for my practice/live room, was that reflections were a lot more even everywhere, and finding room mic locations is a breeze. Because sound is dispersed, no reflections are as strong, and they seem to be coming from nearly everywhere.

what they do not do well is time based diffusion. i'm not really sure how to tell you how this "sounds" because I don't have a lot of experience with qrds, prds, etc... I do know though, that poly "diffusers" are typically not the prescription for back walls of control rooms, because they lack this temporal (time) element.

there is some amount of bass trapping going on here. again, that rockwool fill and the sealed cavity are what's doing the work here. Andre (avare) was instrumental in helping me design these, so he's the one to ask in terms of calculating their performance. What I can tell you is, this is primarily a practice space. With 5 vocal mics set to be heard above a 5 piece rock band (read loud) before the polys were installed, there was a lot of notching going on on the primitive 7 band eq on our Mackie 808s. After the installation, it is running flat, and is crystal clear. It's a bit of a spoiler actually. We've yet to encounter a club that can give us a fraction of quality stage sound compared to our practice space.

Cost? Hmmmm.... the plywood face was "free" as it was salvaged from previous "poor" treatment. I'd imagine a 4x8' sheet of 1/8" luan ply would run you $10 (dependent on grade)? So there's $2.50 a trap. Plus the frame...another $5? You've got an insane insulation deal so what ever 1 sheet of that runs you... some caulk, some screws, some finish washers, sandpaper, varnish, sealer.... Dunno... maybe $15-$20 a trap? Keep in mind the need for cabinet clamps... those ain't cheap.

And time. While you may be able to build these with your eyes closed, the bend time for the face is, or at least should be long. Take your time, and little by little, or else they will crack. If you want to build more than one trap at a time, your going to need 4 more clamps.

In terms of breaking parallel in a live room, and a bit of sound spread without having to get too mathematical or complex, I think these things are great, and I would whole heartedly suggest them to anyone looking for the same!

[Jens Eklund]

More on polys and diffusion here:

QRD and Skyline Well Dividers?

[Glenn Kuras]

Hey John,

Great looking room and also your band sounds pretty darn cool. Do you have a website for your studio??

[johndykstra]

Thanks Glenn!

No website, it's primarily private and close friend use. Who knows, after the control room...

[duff_bdg]

Amazing ... Great work thumbsup thumbsup thumbsup

Duff

[johndykstra]

Here's what I'm thinking, next time I find some free time:



I want to face all of my broadband panels with a binary amplitude grating. Plenty of 1/8" ply left. I figure I can stack them all and drill at once. Deciding if I want to modify a plunge router to hold my drill, or if I should go the drill press route. That would mean buying/renting. Also not sure if a drill press would have the clearance to get into the middle part of the panels. Either way, I think I will have to incorporate a sled/jig to ensure straight lines.

As rendered, the panels are same top and bottom. Even drawing 1/4 of a panel and copy/flipping was tedious. When carried out, I would use the negative for the bottom half, and then I can simply turn ever other trap upside down to avoid repetition.

My reasoning, is that I would like yet a bit more 'life' restored to the room. The polys are great, but the room's decay still feels dry to me.

[Jens Eklund]

I guess you know already, but just like (single) polys, binary amplitude grating panels does not offer any temporal diffusion.

[johndykstra]

Understood.

Given the material is essentially free, and the labor is an extensive set-up...BUT all panels cut at once. Not to mention the face plate is very easily installed given the trap's current construction. Seems a nifty solution. The cost and labor of equal square footage of qrds would be considerably more involved.

Plus, I'll get plenty of qrd experience with the control room.

[johndykstra]

I'm not too happy with how much the top of the panels look like a Chicago Bears logo if you squint. Stupid Bears.

[Jens Eklund]

Originally Posted by johndykstra

Understood.
Plus, I'll get plenty of qrd experience with the control room.