A super easy, super cheap, DIY, wooden, decent looking, sound diffuser design.

Discussion in 'DIY Speakers and Subwoofers' started by BillWaslo, Jan 11, 2015.

  1. I've been setting up a listening room in the basement of our new 104-year old house. After stuffing the low ceiling beams with insulation and hanging a rug (to make a makeshift bass corner trap), the sound in the room was kind of lifeless. Not bad, but not exciting. So I went in search of some sound diffusers. And found that they are WAY expensive, and/or usually difficult to build, particularly the QRD types that usually come to mind.

    But then I ran across some forum posts by Tim Perry, leading to his web pages at Arqen Sonic (http://arqen.com/sound-diffusers/). In the course of his thesis at U. Victoria, he devised and optimized a simple to build, low cost, low profile, diffuser design called the "A1 Leanfuser". This looked like just the thing, but there were two problems. First, Tim's designs were based on 10mm thick lumber, and I'm in USA which is stuck on the imperial inches standards. Second, I'm lazy, and also my table saw is near unusable in a shed across a stretch of Portland rainy-season mud in our back yard. Three problems, actually -- I'm also not wanting to spend a lot (i.e., cheap), at least not until I know more about what I'm doing.

    But nonetheless, I went to the local Home Depot and got some inexpensive furring lumber and some plywood that seemed not horribly off from the pieces in Tim's design. Not terribly close, though, either. I had HD cut the boards to the length (corresponding to diffuser height) I had in mind at the time, 20 inches, and the plywood corresponding to the boards.

    When I found time over the holidays, I finally downloaded the eval version of the diffuser performance simulator software "AFMG Reflex" (http://reflex.afmg.eu/) as Tim suggested and modeled (pretty easy to do) the version of the A1 Leanfuser based on my lumber. It didn't look too bad, actually. But in the meantime I had a change of game plan in where I wanted to use the diffuser -- there was a spectral reflection (shows as a second impulse in the time domain response) off the opposite side of the corner I was setting up the listening area in. Instead of a 5-module 20" high diffuser array, I needed taller arrays, but only about two of those modules wide (about 3 feet total). When using more modules, Tim recommends (and AFMG Reflex concurs) that the modules should be modulated in height to preserve performance. But with two modules, you can't do that and remain symmetric (which I had thought was important for some reason, at the time). So I started playing (in AFMG Reflex) with different arrangement of the same lumber to come up with a ~36" wide diffuser design. The diffuser I came up with is predicted to have quite good performance (see below), though not as optimized as Tim's A1 Leanfuser in depth (the A1 is only about 2" deep, mine are about 4.5" deep).

    Anyway, here is the cross-section design for the Depot Diffuser
    (oops, I accidently hit the Post button too early.... will continue in a reply on this subject!)
  2. ok, here's the Depot Diffuser design:

    The Home Depot part numbers for each wood type are given. These are very cheap furring wood, the 1"x3" (0.71"x2.45" actual) are $2 each for 8 foot lengths, the 1"x2" (0.71"x1.5" actual) are $1 each for 8 foot pieces! Home Depot will make two cuts free per piece of wood, so you can make these diffusers with nothing but a hammer and some nails if you want to. I used a 1.25" electric brad nailer gun, so it only took about an hour to assemble a set of these!

    Here are some links to the wood pieces. You'll want to pick these out in person, since some of the furring lumber will look pretty raunchy, but you can go through the pile and pick out nicer looking ones for the exposed top boards if appearance is a priority.

    Here are some shots of the diffusers set up for test listening in my basement:

    You've probably read about a million times how room treatment will do more for the sound than choice of amplifier, cables, source, etc. Maybe even speakers. Well, I think it's true. These diffusers make a huge positive difference in how the system sounds. Stop messing with the small peanuts expensive stuff and knock up some cheap effective diffusers first!

  3. I like the look of these diffusers more than the conventional end blocks. Cool project Bill.
  4. Thanks Tux,

    Yeah, they certainly look better than the rest of my gnarley basement listening area! I like the shadows and highlight pattern they make when lights hit them.

    I was moving them around last night to see what the effects are. I also have a big roll of cotton felt insulation I'm using as a portable absorber. With the diffusers back more to the side of the seats, the size of the image increases to include some neat ambience from larger area of the room. Cymbal crashes now are really nice.

    I like the sound of diffuser in both locations (where they are in the photos, and where I moved them last night), so I'm heading up to HD this week to get parts for a set of tall diffusers. Debating between floor-to-ceiling or just 4ft tall. Both would be about equally easy to make, the difference is cost of materials. And difficulty in finding enough good looking pieces of the furring lumber. And weight of moving the diffusers - 4ft should be easy, 8ft would start to kick in the procrastination effect.
  5. Those look great Bill, you inspired me to build a set of diffusers.

    Unfortunately I could not use your design due to space constraints from existing treatments, so I decided to adapt/redesign one to fit my space requirements. I hope you don't mind me sharing it here in your thread.

    The spot I intended to place them on my walls is where I had some movie posters residing. I have two posters mounted on each of the side walls in my theater, you can see them in the photo below. The posters towards the front are just far enough forward (with clear plastic being bowed slightly) that they reflect light from the screen when seated in the rear row which I find distracting. So I began searching for something to stick there that was not as visually reflective. Bill starts this thread soon after and I know what I want to do. Here is side wall photo for reference, front poster slightly obscured by beam:


    I looked through Tim Perry's Arqen Sonic website and using the space I had available 28"w x 40"h figured that I could adapt the 5 panel A1-LF stepped diffuser array to use standard 0.75" board thickness as the individual segments. I modeled it using the trial version of AFMG reflex the best I could as the trial limits number of diffuser segments (unfortunately I don't have that data saved and my trial has run out) the model looked quite decent considering the change in aspect ratio of the steps.

    My final design comes out to be 28" wide x 40" tall, using standard 1x4's ripped to three different widths to make up the diffuser segments, it is mounted to 1/2" plywood. Each of the five 7-segment "panels" is 5.25" wide, 7 x 0.75" (nominal 1" board thickness). Now the 5 of those panels comes out to 26.25" so I added a bit of space to the outsides of the overall diffuser and some caps at the ends to make it 28".

    Each of the 5 repeating panels are made up of 7 segments (0", 1.5", 1.9375", 1.125", 1.9375", 1.5", 0"). Those 5 repeating panels are also mounted a different heights (0", 1.5", 2", 1.5", 0").

    In total there are only three different sizes that need to be set on a table saw to cut the 1x4's (1", 1.125" and 1.5". The 1.9375" is the remaining stock from the 1.5" cut). Also only two different sized panels to cut from the plywood (one 28"x40" and three 5.25"x40").

    For each panel the list of components is as follows,

    4'x4' 1/2" plywood:
    (1x) 28"x40"
    (3x) 5.25"x40"

    1x4x8' (x8 - extra board may be needed if you get a crappy board that does not cut well or a piece breaks)
    (all cut to 40" length before hand):
    (10x) 1.5" (Can cut one at this width and one at 1.9375" from in a single pass from a 1x4" with the fence set at 1.5")
    (10x) 1.9375"
    (5x) 1.125" (three per 1x4 section (x2), cut remainder as 1")
    (4x) 1" (three per 1x4 section (x1), with remainder of 1.125" cut to make up the 4 needed)
    (2x) 1.5" (cut both from single 1x4"x40" section)

    I figured it cost me under $30 to build one of these panels.
    I used two of these sheets of plywood:

    and 15 of these 1x4's:

    Now to the fun part, pictures! This may help those who are having a hard time deciphering the numbers above:


    Here is how they look mounted, I may end up finishing them with a stain or an oil or wax, have not decided yet:



    They are quite hefty, I figured about 40lbs. I mounted them using OOK Hangman 6" wide French Cleats (the speaker mounting set, PE sells this but so did Menards so I grabbed it there). They appear to hold the weight just fine (rated to 60lbs) one cleat is mounted to the wall only with drywall screws and it also appears fine.

    Finally the big question how do they sound? I have not listened with them in place for too long (only finished and hung them today) but in running through some familiar demo tracks I felt they made a noticeable impact on the ambiance of the sound. I do notice some sounds tend to reach out wider the front speakers while listening in stereo and to some extent start to wrap around you. This is most noticeable in the rear row where the diffusers are in front of you, unfortunately the front row is lower and you sit below them so I don't expect much change there. No negative effects on imaging, if anything that has also improved but I'll have to listen more to get a better feel for things.
  6. Nice looking diffusers, mtg90. Looks like a fair bit of cutting though, I still don't have my table saw set up at the new place.

  7. What a great topic for this section!!

    I was wondering, could a rigid foam such as urethane or blue polystyrene be used instead of the wood furring strips. It would result in a much lighter construction and you could either paint the foam with a water-based acrylic or hide the panels behind acoustically transparent material such as miliskin spandex.

    Also, does the wood need to be solid all the way to the plywood base panel? Could you use similar size pieces that protrude different heights above the plywood with hollow space behind?

    I'm always looking for a cheaper, lighter, easier solution, although cleaning up foam bits from a table saw and garage is no fun (I have first hand experience....).

  8. This looks great. Do you remember what the effective frequency range is for the resulting panel?
  9. I want to say they worked well down to 700-1000hz, I can't really remember the exact number and unfortunately I never took screen shots while I had the trial of AFMG.

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