Login / Register
 
D. I. Y. Polys
New Reply
Subscribe
johndykstra
Thread Starter
#1
23rd February 2010
Old 23rd February 2010
  #1
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
D. I. Y. Polys

Hey guys,

Thought I would share the build process of my poly diffusers with you. i've gotten two of them completely built so far, here are a few "money" shots:

1.) A close up of the material. The ply face of the polys is an 1/8" thick, 2' x 4'. I wish I could tell you the wood type, but I didn't buy it for this purpose. These panels were the back side of absorption panels I bought from an "out of business" studio sale. I removed the backs of the absorbers to make them more efficient, and had all this beautiful pre-stained ply. It was Andre (avare), who suggested using it for polys. Thank you again.

2.) Here is a shot of a finished poly waiting to be mounted.

3.) And a miniture battery powered "puck" light placed on the upper rim of the frame makes a nice up light. I want to find something with a little warmer color, I just ripped this one down from inside my broom closet.
Attached Thumbnails
D. I. Y. Polys-close-up.jpg   D. I. Y. Polys-lamp.jpg   D. I. Y. Polys-illumination.jpg  
__________________
phantom power doesn't make your voice sound spooky

Here's what I do. Free if you like, pay if you REALLY like:

http://midwestdeathrattle.bandcamp.com/
johndykstra
Thread Starter
#2
23rd February 2010
Old 23rd February 2010
  #2
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Let's get started.

What tools you will need:

Circular/table saw- for cutting the back of the frames, ribs, clapping jig, and front panels to size.

Jig saw- for cutting the rib profiles

Screw gun/drill- duh

Carpenter's hand saw- for sculpting insulation

String & speed square- for translating the radius to the rib

Caulk gun - seal the edges

(4) good sized cabinet clamps- to bend the face

Drum sander- I didn't have one, but it would have been nice to rough cut all the ribs with the jig saw, then stack them and bring them to exact profile uniformly. Not necessary enough for me to convince my wife I needed to buy one.


Materials:

1x4" boards for the ribs
3/4" mdf or ply for frame backs
1/8" ply for faces... make it pretty
2" #8 course thread drywall screws
#8 nickel finish washers
rockwool- ideally as thick as the deepest apex of the rib, but if it's short you can just stuff the extra gap with your trimmings. There's going to be a lot.
Caulk to seal the edges. One tube will seal roughly two traps.
"L" brackets, to mount the polys to the wall
#3
23rd February 2010
Old 23rd February 2010
  #3
Gear addict
 
99zulu's Avatar
 
Joined: May 2009
Location: central ND
Posts: 351

99zulu is offline
That looks really nice! Are you able to measure any difference in the sound now that it's up?

EDIT - sorry, didn't realize you were still posting, I'll hold off on questions until you have the complete project posted.
#4
23rd February 2010
Old 23rd February 2010
  #4
Lives for gear
 
avare's Avatar
 
Joined: May 2004
Location: Hamilton, On Canada
Posts: 4,725

avare is offline
Fantastic! Thanks for sharing with us the construction method also.

Impressed,
Andre
johndykstra
Thread Starter
#5
23rd February 2010
Old 23rd February 2010
  #5
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) My ribs measure 21 3/4" long, by 2 7/8" at the apex. Again it was Andre who gave me the actual circle radius needed to translate how much arc would be appropriate to achieve this design. I forgot to write down the radius to get these dimensions, so hopefully he will pop in with a formula.

[EDIT] here's an online calculator to determine an arc's radius:

Calculator for Radius of an Arc

2.) I screwed a "T" support to the table, with a screw centered at the end of the string to represent the full circle radius. The top of the "T" is to support the rib blank. The middle piece of wood is the actual blank, and the next piece is just there to support my speed square. The pen is duct taped to the speed square to maintain a nice vertical axis. It should be noted, that using string without a lot of "spring" is good, so you can maintain a constant distance. Mine had a little play in it, so I had to redo this step several times.

3.) Close up of the rib in the jig.

4.) Preparing to cut my first rib with the jig saw. IMPORTANT! You will be using several of the "negatives" from the leftover rib stock later to build a clamping jig. Try to salvage a number of convex pieces that are whole. Meaning, don't start cutting the rib out from the apex in one direction, then come back at it from the other way (as I'm about to do in this photo)... this will cut your negatives in half. Ideally, I'd liked to have 5 or so, but I only ended up with two, as this concept eluded me until I was almost done cutting the ribs.
Attached Thumbnails
D. I. Y. Polys-measures.jpg   D. I. Y. Polys-compass.jpg   D. I. Y. Polys-compass-support.jpg   D. I. Y. Polys-rib-cut.jpg  

Last edited by johndykstra; 23rd February 2010 at 09:21 PM.. Reason: awesome calculator!
johndykstra
Thread Starter
#6
23rd February 2010
Old 23rd February 2010
  #6
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) This string represents the width of my face stock

2.) When placed along the arc of the rib line, I am confident that I will be cutting usable ribs. I should note, that I intentional have the string a touch longer than the actual circumfrence of the rib. This will allow my 1/8" ply face to extend past the outer edges of the frame, nearly touching the wall. This will conceal the vertical edges of the frame. I did this by eyeballing, so I can't say exactly how much the over shot is. This was a process. The radius Andre originally gave me was for edge of face to edge of face. Because the back frame is 3/4" thick, I had to adjust the radius on the tracing jig above until I achieved a slightly smaller radius for the frame... again to allow the face panel to extend past it.

3.) You need only to use the tracing jig one time. After you get a rib that is cut, label it as the jig and use it to trace the measurements on to your stock. IMPORTANT. It will be tempting to stagger the ribs, in order to minimize the amount of 1x4"'s needed. (sort of over under... if that makes sense) This is fine, but again, only after you have a number of complete negatives in order to build your clamping jig.
Attached Thumbnails
D. I. Y. Polys-material-1.jpg   D. I. Y. Polys-material-2.jpg   D. I. Y. Polys-jig.jpg  
johndykstra
Thread Starter
#7
23rd February 2010
Old 23rd February 2010
  #7
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) Here is a finished frame, complete with three ribs. The back panel of the frame measures 21 3/4" wide... the same as the ribs, by 42" tall. THe height of the frame will leave 3" top and bottom exposed face panel. (illustrated later). This will allow me to use "L" brackets to mount these to the wall, as well as leave a gap behind the front panel to place those l.e.d. puck lights you saw earlier. This 3" band of poly at the top and bottom of the unit that isn't backed by insulation may adversely affect the acoustic performance of the unit. Again, perhaps Andre will shed his light. IMPORTANT. In an effort to stream line your build, it is crucial to make sure that all of your frames are EXACT in their height, and center placement of ribs. Reason will be illustrated in the next post.

2.) The finished frame with insulation inserted. I cut two rectangles of rockwool that will fit snugly between each rib. Then, using a hand saw, I carved out the profile. You will notice, that my rockwool is 2.5" deep, while the rib measures 2 7/8". I simply filled the tiny gap at the apex with scraps from the trimming process.
Attached Thumbnails
D. I. Y. Polys-frame.jpg   D. I. Y. Polys-frame-stuffed.jpg  
johndykstra
Thread Starter
#8
23rd February 2010
Old 23rd February 2010
  #8
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) Take your time with this, as again, you will be using these measurements from your first piece, and using it as a jig. Because we were already so careful to make sure all of our frames were identical, we can predrill the front panels before they go on. ON THE BACK SIDE OF THE FACE PANEL.. Find your center, and measure in to where your top and bottom ribs are, (where the top and bottom of the frame meet the front ply...roughly 3" in from top and bottom edge). Mark this line... but this is just for centering it later...DO NOT DRILL. Now, measure in from there, the center of the rib stock. Draw that line. Along this line is where you will mark your drill holes. You want one dead center, and move out from there, every 2". If your panels are the same as mine, this will leave you with your last hole 2" from the outer edge of the panel. Then vertically... I'm just gonna draw a sketchup in the next post... this is ridiculous.

2.) steaming the panels to make sure they don't crack. I just used the shower, but if I had my way, we would get one of those garment steamers.
Attached Thumbnails
D. I. Y. Polys-layout.jpg   D. I. Y. Polys-steam.jpg  
johndykstra
Thread Starter
#9
23rd February 2010
Old 23rd February 2010
  #9
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Here is sketch of how I did my predrills. Note, hole size is not actual, but bigger to better illustrate. My predrills were merely pilot holes to prevent splitting. The solid lines on the face are what you will use to center the panel to the frame. The dotted lines represent your lines for drilling. It's good to get your panel predrilled, as it will allow for a straighter line... better aesthetic.
Attached Thumbnails
D. I. Y. Polys-layout.jpg  
johndykstra
Thread Starter
#10
23rd February 2010
Old 23rd February 2010
  #10
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) Place your ply on top of the finished frame. Use your guidelines from the previous step to be sure it is centered. You also need to draw a center line on the rib... in order to center it left to right. Once it is centered, predrill through your center pilot hole on the panel into the rib, and screw it down, THIS SCREW on top and bottom ONLY at this point. I'm using #8 2" drywall screws, with a #8 finish washer. Finish washer isn't just for looks, it provides more surface area for the screw to clamp down on the ply. Put some towels down, and place your clamping jig on top.

IMPORTANT NOTES regarding the clamping jig. Again, I'd have liked a few more negatives to beef this up a bit. Edges would be doubled, and a middle brace wouldn't hurt. It is VERY important to have the overall length of your jig be shorter than the distance between your drill lines... by enough to allow you to drill and screw vertically without interfering with the jig... but not so much shorter that you are distorting the ply as it clamps down. The negative braces need to be somewhat close to the ribs of the actual panel.

The rest of these photos are an attempt to illustrate a slow and even clamping process.

Once the ply is fully touching the rib, predrill through all of your mounting holes, and fasten it down with the screws and washers. Top and bottom ribs only, we'll worry about the vertical mounts in the next step.

[EDIT] You want to drill straight into the ribs on the vertical plane, but follow the arc to determine that you are screwing straight into the rib along the curve. This will allow your screw heads to remain flush and pretty on the face.

[EDIT 2] It's a good idea to not fully snug the screws at this point. Allow the ply to adjust to it's curvature. Come back later and tighten them by hand with a screw driver.

[EDIT 3] We've been saturating the face of the ply with furniture wax, in an effort to keep it from splitting. Dose it before you lay the towels down, and rub it in lightly.
Attached Thumbnails
D. I. Y. Polys-bend-prep.jpg   D. I. Y. Polys-bend-1.jpg   D. I. Y. Polys-bend-2.jpg   D. I. Y. Polys-bend-3.jpg  

Last edited by johndykstra; 2nd March 2010 at 02:22 AM.. Reason: new tips
johndykstra
Thread Starter
#11
23rd February 2010
Old 23rd February 2010
  #11
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) Once your clamping jig is removed, you will see the sides bow up. Don't be alarmed, we ain't done yet. You've already predrilled a number of holes vertically along the sides of the face. Starting at the center rib, push the ply down to make contact, predrill, and screw. The rest of the holes will not be going into ribs, rather, into the back of the frame. Not to worry, there isn't much tension, so the little bite they have is plenty. Get them in, and eyeball the screws depth until you have a nice uniform bend.

2.) here is a shot of the first one I did, next to the newest. I refined the design to allow the screws along the top and bottom rib to extend out further, better spacing (now 2" from the edge, the first one was 3" from the edge). Also, I added more vertical screws. The difference is nominal in the photo, but in real life the consistancy of the curve is much better with more screws, and it puts less tension on each one individually. I will be adding more screws to version 1.
Attached Thumbnails
D. I. Y. Polys-side-raise.jpg   D. I. Y. Polys-old-new.jpg  
johndykstra
Thread Starter
#12
23rd February 2010
Old 23rd February 2010
  #12
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
1.) flip the unit over and prepare it for caulking. Push any loose insulation back in through the crack along the side.

2.) apply caulk to all edges of the frame.

3.) we're reaching some limitations. keep in mind my steaming method isn't quite to ship building or luthier standards. I'd imagine if you live in Houston you could bend this wood into a flute, but up here in wintery Wisconsin, the air is quite dry.
Attached Thumbnails
D. I. Y. Polys-back-no-caulk.jpg   D. I. Y. Polys-back-caulk.jpg   D. I. Y. Polys-crack.jpg  
johndykstra
Thread Starter
#13
23rd February 2010
Old 23rd February 2010
  #13
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Quote:
Originally Posted by 99zulu View Post
That looks really nice! Are you able to measure any difference in the sound now that it's up?

EDIT - sorry, didn't realize you were still posting, I'll hold off on questions until you have the complete project posted.
thanks buddy,

None of them are actually in place yet. I will be posting more as I get them actually installed. As with any single acoustic product, the difference isn't appreciable yet. The plan is to have no fewer than 8 of these in the room.

I've really only looked into using measurement software for a control room setting, where there is a definate target, i.e. mix position. I'd guess ETC measurements at various locations in the room before and after would give a scientific glimpse at what they are doing, but I'm thinking of playing a very dry and sparce drum machine through a speaker, and record it with out the polys, then play the same part at the same volume and re-record it (with the mic in the same place) after the polys are up. After all, many here can attest to my aversion to math and science It's likely I will use a number of mics, all at various unmoved locations, as the differences in before and after will likely be <,> depending on where in the room we are talking.
johndykstra
Thread Starter
#14
23rd February 2010
Old 23rd February 2010
  #14
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Quote:
Originally Posted by avare View Post
Fantastic! Thanks for sharing with us the construction method also.

Impressed,
Andre
Thankyou!

You've been a tremendous help.

Would you mind terribly posting an equation or two for those who are more keen on x's and y's?
#15
23rd February 2010
Old 23rd February 2010
  #15
Gear addict
 
99zulu's Avatar
 
Joined: May 2009
Location: central ND
Posts: 351

99zulu is offline
I for one am very interested in the radius used, and the math involved getting there.
johndykstra
Thread Starter
#16
23rd February 2010
Old 23rd February 2010
  #16
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Here is a sketch of an improved clamping jig. With a sturdy center spine, as apposed to sides, you could screw in your vertical supports while the jig is still in place. I would double up on the end pieces, as it will allow for more area for the clamp to rest on.
Attached Thumbnails
D. I. Y. Polys-spine-jig.jpg  
johndykstra
Thread Starter
#17
23rd February 2010
Old 23rd February 2010
  #17
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
#18
23rd February 2010
Old 23rd February 2010
  #18
Gear addict
 
Magickman's Avatar
 
Joined: Jun 2004
Location: Seattle, WA
Posts: 389

Magickman is offline
Nice write-up.

Thanks!

-MM
#19
23rd February 2010
Old 23rd February 2010
  #19
Lives for gear
 
vespiz's Avatar
 
Joined: Feb 2005
Location: Tampere, Finland
Posts: 594

vespiz is offline
__________________
Cheers,
Jussi Kulomaa
jussi (dot) kulomaa (at) gmail (dot) com
www.masterstroke.info | "Broken" - new album out now!
johndykstra
Thread Starter
#20
23rd February 2010
Old 23rd February 2010
  #20
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Quote:
Originally Posted by vespiz View Post
Looks great!

I found this nifty tool for calculating a radius of an arc! Calculator for Radius of an Arc
fantastic!

using my rib measurements that gives us a

radius of: 1.83379'

while the surface of the arc face spans: 1.89580'

the last .1042' is the amount left over that spans past the frame. (.62" per side)

brilliant.

see, I have been using Andre as my human calculator
#21
23rd February 2010
Old 23rd February 2010
  #21
Gear Guru
 
Glenn Kuras's Avatar
 
Joined: Jul 2005
Location: Atlanta, GA
Posts: 16,174

Glenn Kuras is offline
wow you are a mad man!! Those look GREAT!!
#22
23rd February 2010
Old 23rd February 2010
  #22
Lives for gear
 
vespiz's Avatar
 
Joined: Feb 2005
Location: Tampere, Finland
Posts: 594

vespiz is offline
Quote:
Originally Posted by dykstraster@gmai View Post
fantastic!

see, I have been using Andre as my human calculator
I need calculators

I wanted to know what sized panels I would need to make a poly inside a given frame and this calculator helps.
johndykstra
Thread Starter
#23
23rd February 2010
Old 23rd February 2010
  #23
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
There's far more math to these than just knowing the radius. For example an entire half circle would not do as efficient a job as a smaller slice, and knowing resonant properties of the wood along with the depth of the arc can determine a resonant frequency that your HF diffuser will actually also behave as a panel absorber. Two aspects that Andre took into consideration along with the size of my room to reverse engineer these based on my 2'x4' ply limitation. He's truly an incredible person.
#24
23rd February 2010
Old 23rd February 2010
  #24
Gear maniac
 
mikahanau's Avatar
 
Joined: Aug 2006
Location: Germany /Frankfurt
Posts: 230

mikahanau is offline
Wow
i build my Polys 2 days ago, and they don`t look half as nice as yours

I love the idea with the screws, looks realy cool

cheers
Mika
johndykstra
Thread Starter
#25
23rd February 2010
Old 23rd February 2010
  #25
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Oh, and thank you everyone for the kind words. I'd love to say I'm taking orders to start shipping these out, but they are incredibly labor intensive. Yesterday for example,

clamp jig is already built
frame is already built

I filled and carved insulation

made a new drill template (this was a time soaker)

clamped it down (always a time soaker)

screwed it down

caulked two polys

this all took me 3 hours. keep in mind I'm a heavy smoker, and it's an outdoor only policy in these parts.

oh, and I often step back and look at projects multiple times through the process as well as photos.
#26
23rd February 2010
Old 23rd February 2010
  #26
Lives for gear
 
vespiz's Avatar
 
Joined: Feb 2005
Location: Tampere, Finland
Posts: 594

vespiz is offline
Quote:
Originally Posted by dykstraster@gmai View Post
There's far more math to these than just knowing the radius. For example an entire half circle would not do as efficient a job as a smaller slice, and knowing resonant properties of the wood along with the depth of the arc can determine a resonant frequency that your HF diffuser will actually also behave as a panel absorber. Two aspects that Andre took into consideration along with the size of my room to reverse engineer these based on my 2'x4' ply limitation. He's truly an incredible person.
Bugger! Well, as long as it looks like it works, right?

Seriously, though, good job on these!
johndykstra
Thread Starter
#27
23rd February 2010
Old 23rd February 2010
  #27
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Quote:
Originally Posted by vespiz View Post
Bugger! Well, as long as it looks like it works, right?

Seriously, though, good job on these!
That's not to say someone shouldn't build them without the depth of knowledge, I just so happened to get lucky enough that someone calculated the panels resonance to hit at one of my room modes. Kinda icing on the cake if you will. Granted, he calculated that assuming the frame would be the entire height of the panel, so I may be the one who's buggered it all up.

In terms of the half a circle vs. smaller slice thing, I think you don't want anymore than a third of the circles circumference. Someone smarter will come along shortly I'm sure.
#28
24th February 2010
Old 24th February 2010
  #28
Gear Guru
 
Glenn Kuras's Avatar
 
Joined: Jul 2005
Location: Atlanta, GA
Posts: 16,174

Glenn Kuras is offline
Quote:
Originally Posted by mikahanau View Post
Wow
i build my Polys 2 days ago, and they don`t look half as nice as yours

I love the idea with the screws, looks realy cool

cheers
Mika
Pictures??
johndykstra
Thread Starter
#29
25th February 2010
Old 25th February 2010
  #29
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Hoping to get the bulk of the rest of the polys built this weekend.

I'd like to bounce a test idea off you guys, it's a slight variation of my previous example.

I plan to place my four floor wedges where I would usually record drums, upright & side by side tight in an array... in an effort to get as wide a dispersion of a sound source as I can replicate. I will play through these a drum machine part, again something with some free space to it, and free of reverb.

I will record this with mics placed at various locations throughout the room. SDCs, LDCs, & ribbons... a few in omni, some cardioid, and figure 8. Along with these, I also want to record a di signal.

The di signal is for time alignment.

I want to record the signal twice without diffusion, line them up and do a null test. I'm not sure how well a null test will work in an open air environment, what with atmospheric differences and what not, but this will be sort of my "control". The di is there to confirm that the null is as accurate as possible.

I will then install the polys, and re-record the signal. Without having moved any mic, speaker, or trim knob.

If the null test during the control is promising, than the actual null test could then be viewed as "the sound of the polys" so to speak. What's audible in the null test will have to be looked at suggestively, as some sound will be what the poly adds, and some what the poly subtracts.

If the null test is ineffective, at the very least we have the treated and untreated versions to a/b.

Any thoughts as to how to improve this?
johndykstra
Thread Starter
#30
26th February 2010
Old 26th February 2010
  #30
Lives for gear
 
johndykstra's Avatar
 
Joined: Jan 2008
Location: Midwest
Posts: 4,767

Thread Starter
johndykstra is offline
Here's a screen shot to illustrate the test set-up. For those of you unfamiliar with my live room thread, the framed areas you see on the ceiling represent clouds. The lower breaks in the ceiling line are framed in HVAC soffits.

All room treatment you see (besides polys) is already in place, and will be for both before and after tests. Should give us a very good representation of how these change the behavior of an already well treated room.

I'm going to figure out a way to get all four speakers up off the ground for the test, though it likely won't be a large wood box like you see in the picture.
Attached Thumbnails
D. I. Y. Polys-poly-null-test.jpg  
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
johndykstra / Bass traps, acoustic panels, foam etc
82
jrasia / Bass traps, acoustic panels, foam etc
5
soultrane / Electronic Music Instruments & Electronic Music Production
23

Forum Jump

SEO by vBSEO ©2011, Crawlability, Inc.