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Another DIY Acoustic Panel Build

Discussion in 'Recording Gear and Equipment [BG]' started by kirkdickinson, Jul 31, 2019.


  1. kirkdickinson

    kirkdickinson Supporting Member

    Our church just built a new event center that is basically a gymnasium. The sound is very "echoy". I have been talking to the guy in charge of the building and at some point we are going to have to do some really serious sound treatment. 100's of panels. I told him that I have been watching some youtube videos and I think we could have a work day at the church and build them ourselves. We are in no hurry, this will probably happen a year or so down the road.

    I had all these ideas spinning around in my head so I decided to build some as a proof of concept. Instead of building them to hang on a wall, I wanted to make some portable, modular panels that could be used behind a drum kit or in a studio. I wanted the panels to be able to be quickly set up in different configurations.

    I decided to use the soft Rockwool insulation 3-1/2" thick. It takes up more room, but should absorb a wider frequency range both of highs and lows. I guess from my reading that 3-1/2 Rockwool at this density won't do much for bass below 60HZ but should work well for all other frequencies.

    A panel that is thicker with the higher density rockboard on the back would really handle the lower frequencies better. I may try some other designs.

    Here is what I did:
    [​IMG]
    Those pieces are 4-1/2” x 72” three-quarter plywood with hinges mounted to both sides. There are 10 of them.

    These are the side pieces with the hinges routed in, pre-drilled with a self centering drill bit and attached for fit. I used a master and all the hinges were fit in so that they all attached to the same master.

    [​IMG]
    Here are the end pieces (3/4" plywood) and the top and bottom corner stiffeners. (1x3)

    All of them pocket hole drilled and ready to assemble.

    [​IMG]
    Some of my tools. Didn't plan this shot, but it kinda looks like I did.


    [​IMG]
    Frames assembled except for spacer frame to keep the backing in.

    [​IMG]
    I wasn't sure if I would need to cut away the felt later to make the hinges work correctly, so I painted all the hinge points black if that would possibly show through.

    [​IMG]
    Here is a frame with the frame in for the backing material. I used 1x material and ripped it down to 3/4"x1". Everything is assembled with wood glue and pocket screws and or a brad nails.

    [​IMG]
    The back won't be covered, so I painted it with a few coats of flat black.

    [​IMG]
    Here is a close up of the frame inside for the backing. The little strip on the 1x3 is a 1/4"x3/4" rip to make the boards meet up for the backing.

    [​IMG]
    The backing material is simple landscaping fabric.

    [​IMG]
    Fabric is stapled down to the frame inside.

    [​IMG]
    Trimmed off with my handy switchblade utility knife. That thing is cool.

    [​IMG]
    Frames assembled ready for rockwool.

    [​IMG]
    Rockwool
    Lowes did not stock the 24" wide Rockwool, so I had to special order it.

    [​IMG]
    Had to order 3x as much as I needed to get the minimum order. I have enough left to build 10 more of these panels.

    [​IMG]
    I decided to put a center support in. The frames were bowing in because of the tension of the landscape fabric on the back.

    [​IMG]
    Sprayed contact adhesive on the frame and the felt.

    I started with DAP brand and found that it allowed some positioning after it was attached. Unfortunately, it also didn't stick as well. I have some loose spots on a couple that were done with DAP.

    When I ran out I got some 3M and that stuff sticks instantly. No chance for repositioning, but it won't ever come off either. Will only use 3M if I ever do more.

    More on next post.....
     
    Last edited: Aug 2, 2019
  2. kirkdickinson

    kirkdickinson Supporting Member

    [​IMG]
    Felt stuck to the top
    [​IMG]

    [​IMG]
    Here are all five finished with all the hinges attached.

    [​IMG]


    [​IMG]
    I ordered some amplifier feet to attach to the bottom. I made a template and they should all be exactly attached in the same place. One looks out in this photo though. ???

    I spaced them from the corners in case I want to put corner protectors on.


    [​IMG]
    Here is the whole stack of them standing upright with all the hinges linked up.
    [​IMG]


    [​IMG]
    Here it is set in a semi-circle. Sorry for the bad lighting. 10PM in the garage.
    [​IMG]

    [​IMG]
    Loaded up in the truck for transport. Didn't realize that my 6' bed is not really 6'.

    [​IMG]
    Not how I planned to set it up, but because of the way the hinges are attached. It is very versatile and has many possible setups.

    [​IMG]
    Set up in a friends basement home recording studio. First task, two different amps at one time. Set up in an H pattern.

    Possible setups...
    [​IMG]
    Semi Circle Setup
    [​IMG]
    Accordion Setup
    [​IMG]
    Double "Y" Setup

    Price for 5 panels 24"x72"x4-1/2" thick (figured as close as I can)
    24” rock wool insulation for 2x4 walls $60
    1 sheet of 3/4 plywood $25 (cut in 4-1/2" strips)
    2 1x3x8 pine $4 total (for top & bottom corner reinforcement)
    2 1x2x8 pine $3 total (for front stiffener)
    2 1x6x6 pine $14 total (for ripping down into 1" strips for backing)
    1 box Kreg 1-1/4" Pocket Hole screws $5
    7 yards charcoal craft felt $49 total
    Basic Landscape fabric $13
    Gorilla Glue $3 (used 1/2 bottle from my supplies)
    Brad Nails $2 (used from already purchesed stock)
    Staples $5
    3M super 90 Spray Adhesive $39 (3 cans at $13)
    Black GlideRite hinges $24
    Rubber Feet $10

    ---------------------------------

    $256 / 5 = $51.20
     
  3. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Those are very clean looking panels. Nice job.

    This is a common misconception as confirmed by Rod Gervais, John Sayers and Ethan Winer. There’s also an excellent write-up on the Ready Acoustics website about it, which you can find here: Yes, but I have read that higher density acoustic insulation (like OC705) is better for low-end absorption. Ready Acoustics!. Increased depth and lower density (increased porosity) is the way to handle lower frequencies, but since it requires an ever-increasing amount of floor space the lower you go, the less viable it becomes as a solution for most folks. The reason why OC703 is the commonly used standard is because of its 3pcf density, which offers excellent performance in the upper bass and lower midrange, without too much of a hit to the midrange and high frequency content.

    Rockwool is around 1.4pcf, which should be good for low end absorption provided there’s enough of it in terms of thickness. You can increase performance by placing an air gap behind the panels when you get to mounting them on walls and ceilings.
     
  4. kirkdickinson

    kirkdickinson Supporting Member

    Thanks.

    Mine have a 1" air gap built in on the back if they are placed right up against a wall.

    Since I have enough Rockwool to make 10 more panels, I am thinking of making the next 5 so there isn't a back. Make them look the same on both sides so they are nicer looking on the backside.

    I will have to do some more reading about this. When we actually work on the church building and build a bunch of panels, the rockboard would definitely be easier to frame and hang than the rockwool. Just not sure it will cover the frequency response. In a gymnasium, wood floor, concrete walls, etc.... most of the problem we are seeing now is in the mids and high frequencies.

    I know the less dense material absorbs the highs and can make too dead of a space, but when you have 10's of thousands of square feet of walls to cover, you can only cover a percentage of that. The left over bare walls, and wood floor will still reflect and we won't end up with a dead sounding room... ever.
     
  5. IconBasser

    IconBasser Scuba Viking Supporting Member

    Feb 28, 2007
    Fontana, California
    Those look great, Kirk! You're definitely a more skilled craftsman than I.

    The one concern I'd have with a build like that is the weight - those frames don't look light. Heaving around 5 at a time looks like it could be a bear.
     
  6. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    A 1" gap won't do much for increased performance, but it will definitely help. If you can add rubber stand-offs to increase that gap you'll see improved low end performance. The point of diminishing returns usually hits at about 1.5 times the panel thickness, or so I've read. Most pros advocate for an air gap equal to the thickness of the absorbing material if possible. That's usually a tough pill to swallow when floor space is at a premium, but that doesn't sound like a concern for your space.

    That could be the case, and you'd know better than anyone. That said, I've never seen a room where treating the low end first wasn't the right move. I'd deal with the lows that are feasible (i.e. upper bass and lower midrange), and then step back to see how things end up sounding.

    This is easily remedied by picking a lower pcf material that has a kraft paper backing, but given the specifics of your space it seems unnecessary to ever worry about things being too dead.
     
  7. kirkdickinson

    kirkdickinson Supporting Member

    I am really not much of a craftsman, but I did spend a lot of extra time staring at it and trying to figure out how to make it look better.

    I didn't weigh them. I meant to weigh one before I hauled them over to a friends house. Wrestling all 5 by myself was a little rough. But I carried two at a time easily down rickety basement stairs. I would guess they weigh about 20-25 lbs each.
     
    Last edited: Jul 31, 2019
    mikewalker likes this.
  8. kirkdickinson

    kirkdickinson Supporting Member

    We probably won't do much with this until the church actually hires the system integrator to do the sound system design. Apparently the roof decking is slotted with some type of insulation above it. It is supposed to be some type of sound panel. I do think the gym is a lot less live than others that I have been in.

    Right now, I am having fun with my spare time and tools in my shop.

    Thanks for all the comments. I am woefully uneducated in this area. I found the spreadsheet to calculate for porous absorption. I am completely lost with that. :)
     
  9. higain617

    higain617

    Sep 12, 2013
    WA
    Individual ones would make good bass traps for corners.
     
    kirkdickinson likes this.
  10. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    The Whealy Calculator? Yeah... Me too, haha. I've read enough anecdotally from experts in the field to just go with that. The spreadsheet loses me.
     
    kirkdickinson likes this.
  11. hawk400

    hawk400

    Oct 26, 2013
    Hinging them is straight out of theatre , nice and flexible...long pins with a 90 degree bend makes assembly and breakdown easier. Did some similar panels recently, same framing, only used two thicknesses of sonopan with about 2" of air space between them. Wrapped with cloth, then strategically hung in a music room... the guy is happy

    Home | Exceptional Soundproofing SONOPAN
     
    kirkdickinson likes this.
  12. kirkdickinson

    kirkdickinson Supporting Member

    Never worked in theatre. The hinge pins are not the easiest to remove. I like the idea of long 90 degree pins. I may have to make some.

    Where do you purchase Sonopan and is it similar to rockboard 705?
     
    hawk400 likes this.
  13. hawk400

    hawk400

    Oct 26, 2013
    It's available locally in Canada, just found out it's made here, don't know about distribution stateside.. not familiar with the rockboard, though it looks like compressed fibreglass baton. Sonopan comes in 4' x 8' sheets by 5/8" thick, think it's made of wood fibres like tentest only perforated with 1/16" holes on a 1" grid. There must be an equivalant if they don't ship there.
     
  14. hawk400

    hawk400

    Oct 26, 2013
    these are listed on their site... Firefox_Screenshot_2019-08-01T02-29-29.128Z.
     
  15. Bboopbennie

    Bboopbennie

    Jun 16, 2019
    kirkdickinson likes this.
  16. kirkdickinson

    kirkdickinson Supporting Member

    Hung out with some friends in the late 80’s that spent a month at Amigo Studios in LA. I remember those mobile sound walls. Some were pretty big.
     
  17. The Chuck

    The Chuck

    Dec 11, 2013
    Wilmington, NC
    Very nicely done!

    I also used Roxul. I made 6 single width and 2 double width panels. That was enough to provide the coverage I was looking for in my home studio. -see avitar for old house pics below new house.

    I made the frames out of 1X4 pine (from Lowes) and stained them. The fabric is actually some red burlap that I got cheap at Joann Fabrics.

    EDIT- Don't forget about diffusion. There are lots of DIY options for building those as well and they can bee a very useful tool for taming a room.



    upload_2019-8-1_10-9-26.

    upload_2019-8-1_10-9-37.
     
    Last edited: Aug 1, 2019
    kirkdickinson likes this.
  18. kirkdickinson

    kirkdickinson Supporting Member

    Nice panels. I like the stained wood. That looks like a less labor intensive method than what I used. How did you attach the burlap? Is there a furring strip that you stapled to?

    I love Joanne's Fabrics I spend too much time in there every time I go. I wonder if the employees there think I am some creepy old bearded man? After all, I am usually the only man in the place.

    I have seen some of the diffusion walls made out of varying lengths of wood, even found a calculator where you input the frequency you want and it tells you the lengths and locations to attach them. Looked like another fun project. I have also seen some of the diffusers made from the cardboard concrete forms.
     
    Last edited: Aug 1, 2019
  19. The Chuck

    The Chuck

    Dec 11, 2013
    Wilmington, NC
    Diffuser panels can also be a big help in large spaces. Lots of easy to built DIY stuff on them online.
    Ahhh- it is actually a wood frame inside of a wood frame. The burlap was stapled to the first frame and the the second built around it. Not the best way to do things but it was on the fly and it turned out well.

    I had made some kind of like the ones below for my old studio. That room was much bigger that my current room so I had no more need for them when I moved.

    This types are pretty easy to make-

    upload_2019-8-1_15-28-19. upload_2019-8-1_15-28-27.
    upload_2019-8-1_15-28-39.
     
    Bboopbennie and kirkdickinson like this.

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