DIY Sound Diffusers - Page 14 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 64Likes
Reply
 
Thread Tools
post #391 of 406 Old 01-21-2017, 06:30 AM
AVS Forum Special Member
 
jkhome's Avatar
 
Join Date: Jun 2003
Location: Virginia Beach, Va., USA
Posts: 1,570
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked: 65
Quote:
Originally Posted by aackthpt View Post
Actually latex paint does this. Jens Eklund (from Gearslutz) sells an EPS diffuser (QRD-ish but without fins, designed with AFMG Reflex, made on a CNC hot wire machine) and he's tested the amount of absorption reduction based on painting. It was not small, but I don't have the reference handy nor the will to find it... should be easy to Google.
I've read Jens Eklund's comments, totally agree. Although not completely diy, I made up some QRD diffusers using 2 x 2 pre-made unfinished EPS panels, from SRL acoustics. Used them for a while un-painted, and they did absorb sound much more (not what I wanted). Mostly in the treble range.

Even with starting with premade panels, the finish work still was very time consuming. I had to machine plum the panels to fit the boxes that held them, seal the edges and centers with caulk and paint. One coat of latex primer and three coats of latex flat wall paint (same color as the walls and ceiling of room). Used foam brushes to get into the inside surface, then regular brush to even things out. Got it down to two hours per coat per panel. Mounted in 1 x 8 diy oak boxes, on modified Sound Anchor stands (for Maggie MMGs) and casters.







Cudos to you guys who are making these from scatch.
ellisr63 likes this.
jkhome is offline  
Sponsored Links
Advertisement
 
post #392 of 406 Old 01-21-2017, 04:49 PM
Advanced Member
 
12B4A's Avatar
 
Join Date: Mar 2014
Location: CR Iowa
Posts: 614
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 367 Post(s)
Liked: 260
Quote:
Originally Posted by gworrel View Post
That looks amazing. So more details please about how you managed to get this done. I assume this was done with some sort of expensive CNC water jet. Who typically has these things and how much might they charge?
Thanks! It ended up being about $50 per panel for 8 panels shipped. Basically, I sent the .dxf of the 2D cut pattern to Foam Factory (Macomb, MI) that does water jet, hot wire, etc. They were willing to do the job. I did try to get someone locally but they were not willing to do it because the pattern in my file "was all wrong" and they were estimating a 20% material waste. I think if I had pinged more shops in the country I may have gotten a significantly better price on the material line item but Foam Factory seemed like a sure bet. With specialty jobs like this, looking for the lowest bidder often is more expensive down the road unless you know a guy who knows a guy.

That craiglist ad probably does charge $1 for the cutting but $200/hour for knowing where to cut.
ellisr63, dgage and gworrel like this.

Life is Lambertian
12B4A is offline  
post #393 of 406 Old 01-21-2017, 07:30 PM
Advanced Member
 
gworrel's Avatar
 
Join Date: Dec 2005
Location: Detroit
Posts: 683
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 368 Post(s)
Liked: 321
Quote:
Originally Posted by 12B4A View Post
Thanks! It ended up being about $50 per panel for 8 panels shipped. Basically, I sent the .dxf of the 2D cut pattern to Foam Factory (Macomb, MI) that does water jet, hot wire, etc. They were willing to do the job. I did try to get someone locally but they were not willing to do it because the pattern in my file "was all wrong" and they were estimating a 20% material waste. I think if I had pinged more shops in the country I may have gotten a significantly better price on the material line item but Foam Factory seemed like a sure bet. With specialty jobs like this, looking for the lowest bidder often is more expensive down the road unless you know a guy who knows a guy.

That craiglist ad probably does charge $1 for the cutting but $200/hour for knowing where to cut.
The Foam Factory is about a 45 minute drive away from me. Looks like they did a great job. There are a lot of small machine shops around here, but a place that specializes in foam seems like a wise choice. Did you come up with the dxf file yourself? Would you be willing to share it? I don't know exactly where I would use these but the idea is intriguing. Even with the 3lb density, I calculate your total weight at about 31lbs. Seems much better than the ones made of wood.

Off topic, but just last week I went to go pick up some mail that had been delivered to a former business location and the new tenant was a small machine shop. They had a number of large machines with windows and you could see streams of water and some kind of cutting going on. The owner showed me some prototype aluminum pieces they were making for the auto industry including what looked like a valve cover with a cobra symbol on it. Cool stuff.
ellisr63, dgage and mtbdudex like this.
gworrel is online now  
 
post #394 of 406 Old 01-21-2017, 07:46 PM
Deep Sea Sound
 
dgage's Avatar
 
Join Date: Dec 2003
Location: Knoxville, TN
Posts: 3,431
Mentioned: 183 Post(s)
Tagged: 0 Thread(s)
Quoted: 1662 Post(s)
Liked: 1480
I looked up what a water jet machine would cost and though there MAY(?) be a cheaper version for foam, the ones for metal start at $80,000 and go WAY up. So looks like a great deal for a really nice diffuser.

David Gage
Deep Sea Sound
"You don't listen to our subs, you EXPERIENCE them!"
dgage is offline  
post #395 of 406 Old 01-21-2017, 07:53 PM
Advanced Member
 
12B4A's Avatar
 
Join Date: Mar 2014
Location: CR Iowa
Posts: 614
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 367 Post(s)
Liked: 260
Yeah, I can share it. Sometimes at my job I use a laser cutter and need to generate my own cutting files so this wasn't too much trouble. If someone else can take this and get it done for a more competitive price, please let me know. I may want to do more in the future.
Attached Files
File Type: zip 2inch diffuser.dxf.zip (10.1 KB, 92 views)
ellisr63 and mtbdudex like this.

Life is Lambertian
12B4A is offline  
post #396 of 406 Old 01-23-2017, 10:10 PM
AVS Forum Addicted Member
 
noah katz's Avatar
 
Join Date: Apr 1999
Location: Mountain View, CA USA
Posts: 21,562
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1095 Post(s)
Liked: 380
12B4A - very nice!


Quote:
Originally Posted by gworrel View Post
This guy on craigslist only charges $1: http://detroit.craigslist.org/okl/hvo/5952780109.html
The $1 price is a common craigslist tactic to not be eliminated from a search filtered by max price
noah katz is offline  
post #397 of 406 Old 02-26-2017, 10:48 AM
Advanced Member
 
12B4A's Avatar
 
Join Date: Mar 2014
Location: CR Iowa
Posts: 614
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 367 Post(s)
Liked: 260
Just a little update on the outcome of the EPS 2D diffuser project:

Everything seemed to work out well. After a testing Camie 373 as the adhesive, I went with Glidden Gripper primer instead. The Camie does eat EPS while the Glidden goes on easy, dries in 30 minutes, fully cures after 24 hours, and just plain works as an adhesive. Since I had black fuzzy squares up on the ceiling already, I just adhered the hook side of velcro to the diffusers and then pressed them against the ceiling. Nothing has fallen down in the last few weeks so I'm calling it good.

Getting treatment up on the ceiling really makes a difference and made the whole effort worthwhile. Using a portable speaker while walking between rooms is a nice "this is what happens when you reduce slap echo" demo. I can only describe it as becoming cleaner without making it duller.

Attached Thumbnails
Click image for larger version

Name:	2d skyline.jpg
Views:	686
Size:	245.5 KB
ID:	1994121  
ellisr63, dgage, Eyleron and 4 others like this.

Life is Lambertian
12B4A is offline  
post #398 of 406 Old 04-03-2017, 05:25 PM
Advanced Member
 
12B4A's Avatar
 
Join Date: Mar 2014
Location: CR Iowa
Posts: 614
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 367 Post(s)
Liked: 260
Got a lot of panels to BAD....

Attached Thumbnails
Click image for larger version

Name:	BAD panels.jpg
Views:	506
Size:	151.2 KB
ID:	2066505  

Life is Lambertian
12B4A is offline  
post #399 of 406 Old 04-03-2017, 05:39 PM
AVS Forum Special Member
 
jkhome's Avatar
 
Join Date: Jun 2003
Location: Virginia Beach, Va., USA
Posts: 1,570
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked: 65
More BADness, just added the curved panels this weekend.


Last edited by jkhome; 04-04-2017 at 05:54 AM.
jkhome is offline  
post #400 of 406 Old 04-04-2017, 01:51 PM
AVS Forum Special Member
 
asarose247's Avatar
 
Join Date: Mar 2010
Location: DIY enabled in SoCal / OC
Posts: 3,140
Mentioned: 56 Post(s)
Tagged: 2 Thread(s)
Quoted: 823 Post(s)
Liked: 635
^

looks wonderful . .

makes me think the vertical slots could be easier for the non-CNC crowd

DIY FAN Denon X5200 , ATI A 2000 for 7.4.6 SCATMOS/DSU/SHARP 80" LED/LCD
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x Inuke6000DSP
www.avsforum.com/forum/155-diy-speakers-subs/1485120-submaximus-large-front-loaded-horn
http://www.avsforum.com/forum/155-di...orn-build.html
asarose247 is online now  
post #401 of 406 Old 04-04-2017, 05:43 PM
AVS Forum Special Member
 
jkhome's Avatar
 
Join Date: Jun 2003
Location: Virginia Beach, Va., USA
Posts: 1,570
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked: 65
Quote:
Originally Posted by asarose247 View Post
^

looks wonderful . .

makes me think the vertical slots could be easier for the non-CNC crowd
They have 1/2" holes, drilled with a forstner bit. Used a hand drill, drill guide, and about 6-7 hours labor (plus breaks). That's not counting the time first drilling the HDF template, which was a false start because it couldn't handle the bend. So used it as a guide on the panels shown, which are a thin birch material. Then mounted those on an existing diy absorber, with aluminum mirror channel and metal L shelf pins as stops.





First tried the combo on the speaker's first reflection locations, but later decided to mount them on the bass traps on the rear wall. Very happy with the results now.
OJ Bartley likes this.

Last edited by jkhome; 04-07-2017 at 08:18 AM.
jkhome is offline  
post #402 of 406 Old 04-04-2017, 07:10 PM
AVS Forum Special Member
 
asarose247's Avatar
 
Join Date: Mar 2010
Location: DIY enabled in SoCal / OC
Posts: 3,140
Mentioned: 56 Post(s)
Tagged: 2 Thread(s)
Quoted: 823 Post(s)
Liked: 635
^
OMG!

A 6 or 7 hour job, with some breaks, all by hand . . .

glad it had the happy ending . .

DIY FAN Denon X5200 , ATI A 2000 for 7.4.6 SCATMOS/DSU/SHARP 80" LED/LCD
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x Inuke6000DSP
www.avsforum.com/forum/155-diy-speakers-subs/1485120-submaximus-large-front-loaded-horn
http://www.avsforum.com/forum/155-di...orn-build.html
asarose247 is online now  
post #403 of 406 Old 04-05-2017, 10:08 AM
Member
 
Adhoc1's Avatar
 
Join Date: Apr 2009
Posts: 91
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 38
Good and nice work jkhome! If you are considering making more BADs, and use them as broadband helmholtz absorbers for ”lower frequencies”, make the holes smaller. Like Ø 10 mm / 3/8” instead of 12,7 mm / ½”, to get around 9% open area (or lower) if you use a 24”x 24” module as surface area. (With ½” holes the open area gets a bit too large I think, if one wants to keep the energy in midrange and treble more intact that is and concentrate more on absorbing the lower range.)

I think you kept about the same tempo as I did, 3-4 rows of holes in 15 minutes then a break. Darn tedious and boring work but not hard really. I have 2x4 modules curved BADs on each side wall and another 5 BADs at the backwall in my room. My opinion is that they work well. Good absorbtion, and some diffusion even if a 1D QRD would be more effective than BADs.





jkhome and OJ Bartley like this.
Adhoc1 is offline  
post #404 of 406 Old 04-05-2017, 12:35 PM
Advanced Member
 
OJ Bartley's Avatar
 
Join Date: Apr 2009
Location: Toronto, ON
Posts: 743
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 259 Post(s)
Liked: 347
hmmm, BAD panels over bass traps... why have I never thought about that before? It seems that lately the gurus are saying that bass traps in the front corners aren't optimal. I wonder if BAD panels placed over bass traps in front, and combined with either "linacoustic/poly layer/linacoustic" or strategic panel placement on the rest of the front wall would be a good option.
ellisr63 likes this.
OJ Bartley is offline  
post #405 of 406 Old 04-05-2017, 03:58 PM
Member
 
Adhoc1's Avatar
 
Join Date: Apr 2009
Posts: 91
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 38
Remember, if you want to have a broadband helmholtz absorber for lower frequencies in combination with the somewhat diffusing BAD panel front, you have to secure the panel over an air tight ”box” behind the panel. Open area percentage + thickness of the panel + box depth and gasflow resistivity of the insulation filling will determine over which frequency range it will be effective (alfa > 0,8). I think the Linacoustic has too high gasflow resistivity to be best possible choice, unless you are bound to have a very thin / narrow box depth. A curved panel show better performance for scattering / diffusion compared to a flat panel.

The diagram show a simulation of the BADs at my back wall corners. Blue line is with ”low” gas flow resistivity 6000 Pa x s / m² (like common light weight wall insulation). The red line with ”high density” insulation with about 33 000 Pa x s / m². In both cases with 4 mm thick plywood panel, about 9,2% open area and 260 mm depth. I actually managed to make them 300 mm / 12” thick, so absorbtion should be a bit better in the very low frequencies.



Some links on gas flow resistivity for various insulation: http://prorecordingworkshop.lefora.c...62eeadd7e7.pdf and http://www.gearslutz.com/board/bass-...er-sweden.html The Isover info in: https://www.gearslutz.com/board/12493263-post34.html (disregard DanDans ramblings)

A usable calculator for modeling: http://www.acousticmodelling.com/multi.php

In general: use ”low” density / gas flow resisitivity for larger insulation depth, > 8” or so, use ”higher” density / gas flow resisitivity for narrow insulation depth, < 8” or so.
ellisr63 and dgage like this.
Adhoc1 is offline  
post #406 of 406 Old 04-05-2017, 06:07 PM
AVS Forum Special Member
 
jkhome's Avatar
 
Join Date: Jun 2003
Location: Virginia Beach, Va., USA
Posts: 1,570
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked: 65
Quote:
Originally Posted by Adhoc1 View Post
...I think you kept about the same tempo as I did, 3-4 rows of holes in 15 minutes then a break. Darn tedious and boring work but not hard really. I have 2x4 modules curved BADs on each side wall and another 5 BADs at the backwall in my room. My opinion is that they work well. Good absorbtion, and some diffusion even if a 1D QRD would be more effective than BADs.
Your panels look awesome, and thanks for the additional info. Yeah, after a few rows I would stop and vacuum up the mess, to keep things cleared out. After a while I could tell when it was time to change out the drill bit. Bought three bits so just divided the panel holes into three sections and changed the bit after each section was done. With also a beer break between bits

From what I have read the 1/8" HDF (aka masonite) is usually recommended as the panel material to be used, but I found that stuff hard to get clean cuts on the backsides, and even harder on the bits. For me it will be plywood for any other BADs moving forward.
ellisr63 and dgage like this.
jkhome is offline  
Sponsored Links
Advertisement
 
Reply DIY Speakers and Subs

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off