How I built my bass traps...

[apadua]

I'll bite.. I posted this on another site.. but I thought I would share here too.

The company that I work for moved buildings and were throwing out their cubicle partitions (3 floors worth)..I opened one up and it was OC703.. I felt like I won the lottery...

This is just one truck load.. I loaded up for almost 2 weeks and there was still some left over

Another angle

With the metal frame.. which I had to remove (Hammer)


Exposed OC 703.. Had to cut alot of fiberglass with an exacta blade.. Itchy stuff. I used a dust mask and a long sleeve shirt and pants (no shorts!!!) .. Did I mention that that stuff is itchy....

Wood from Home Depot.. They cut it to my specs for 81 cents a cut

Approx 6 inches deep.. to be filled with 4 inches of OC 703 and then 2 inch gap to space it off the wall

Dry wall screws..

[apadua]

Screws in place

Frame

Frame is done

Frames are done.. Sizes (6X2, and 5X2.5)

It's wrapping time.. (Burlap, got this for free too)

Measure and cut fabric & Fill with OC 703

Just to make sure I still have my precious "air-gap"

L bracket to secure panel

"Like a glove"....

[apadua]

Corner Cut

Fold in.. then wrap

Tuck fabric in with flathead screwdriver

Staple

Trim Top & Bottom Edges

Febreeeze those Mutha's !!!!!!!!!! And bake in the beautiful San Diego Sunshine!!! 75 degrees in February....

All done..........

[embrionic]

Originally Posted by apadua

L bracket to secure panel

how did you do your "invisible mount" system with the L bracket inside/behind... i mean how did you access it once the panel is built, to screw it to the wall?

thnx

[SaSi_SiDi]

I don't think that's an invisible mount. It's just a bracket to keep the fiberglass block from falling off.

I would employ that screw hole in the L brackets (at least four of them) to thread some string in X fashion and retain the block better.

[embrionic]

Originally Posted by SaSi_SiDi

I don't think that's an invisible mount. It's just a bracket to keep the fiberglass block from falling off.

hmm... you might be right, he says "secure the panel" but he might mean the fiberglass panel.

[Lemonsqueezer]

Its mounted in the middle of the depth of the wood. If it was for mounting I am sure it would be flush with the back.

[poshook]

Bass frequencies are omnidirectional. Standard room has 4/12 corners with potencial bass problems. Most of people use basstraps only for 4 of them...

[JBaptista68]

Here are some photos of the bass trap and broadband absorbers we are building. We used a thinner MDF for the surround. Almost impossible to find any 24" insulation around here so we went with 16" x 48", but we will have to build more of them.

In order to build a whole bunch of these we decided to build a template and then build a prototype to make sure we didn't have any bugs. This is what a whole bunch of traps looks like in pieces. It took us almost half a day to cut all of the pieces.



Here is the template for the traps. Each piece slides in and is held up so that it is easy to nail it all together. Each piece gets nailed together.



Once nailed together, you've got a nice neat box.



The material is held together with a small border piece that gets nailed one inch inside of the frame.



Once the unit is done we decided to paint it black. The material gets tightly stretched and stapled to the inside of the border. The insulation then snugs in nice and tight and it really looks clean. Here is a picture of the first trap up on the wall. We took all of our paint swatches into the fabric store and we were able to find this really nice sheer fabric in a huge pile of colours.

[apadua]

Originally Posted by embrionic

how did you do your "invisible mount" system with the L bracket inside/behind... i mean how did you access it once the panel is built, to screw it to the wall?

thnx

I screwed in (not pictured) eye hooks about 1 foot down from the top then strung picture wire through the eye hooks. Hung/ mounted the panel using the wire and "ooks"

[JBaptista68]

Here are some more pictures from tonight. We got most of the front wall done. Still more to come...

[JouCalle]

First post, great forum!

If I build my own porous absorber, what materials can I use to deflect high frequences?

[666666]

Wow, great info / pics in this thread! Neat!

I just finished my frames so I figured I'd throw up some pics too.

I used standard 1"X6" pine strips from Home Depot. They're 5.5" wide. I wanted to make this work because it would have been a real pain (plus a lot of extra work) to have to "rip" a bunch of strips on a table saw to yield a specific size. I was determined to make a standard size work... and as it turns out, 5.5" is going to be perfect.

The goal is to stuff the frames with two 2" thick sheets of OC 703 (4" of 703 total per trap). But then there's an extra 1.5" left over inside the frame.

Then, you'll notice I used some extra pine strips as frame "supports"... these strips not only keep the frames rigid, but act as a support also for the 703 (so the 703 doesn't pop out the back)... these "supports" are standard 1"X3"s from Home Depot and are 0.75" thick. Since the 703 will sit "on-top" of these supports, there will be an effective air gap of 0.75" behind the 703. So the supports provide a helpful 0.75" air gap while also supporting both the frame and the 703. I've now accounted for 4.75" of my trap guts.

For the last 0.75", I will be adding a layer of 0.75" thick (10oz per yard) polyester batting on top of the 703. This is because I plan on wrapping my 703 in thin plastic sheeting to hold in any dust or vapors (I have bad allergies and am very sensitive to this stuff). I do not want to have any reflections off the plastic, so the 0.75" layer of batting on top will eat up anything that would have reflected off the thin plastic. And that takes care of the 5.5".

So, to recap, from back to front: 0.75" of air space, 4" of 703, and then 0.75" of batting... and this all fits perfectly in a 5.5" (standard 1"X6") frame.

Plan is to then cover it all with black felt. Thick felt would have been nice, but the local fabric store had a good price on fairly thin felt, it passes air quite nicely so I'm not complaining. The felt over the thick batting should be more than enough to stifle any potential high-frequency reflections off the 1-mil plastic sheeting that will be covering the 703.

First pic below is of the three sizes I decided to make. My room has obstacles so having these three sizes allows me to get trapping where I need it. Shown here is a 2'X2', 4'X2' and 6'X2'. The way I designed them, there was not even one inch of scrap wood left over. I used every last inch of wood I purchased. For the 2'X2's and 4'X2's, I used 8' long pieces (they fit in my truck easy). For the 6'X2's, I split 12' long pieces (those had to go on the roof rack). It's important to conserve material if you wish to keep the cost down because "waste" can really add up. Need to plan carefully.

Oh yeah, in order to make these frame sizes and not waste any wood, the INNER dimensions of the frames have to be a bit smaller than the standard dimensions of the 703 (which is 4'X2'). So this brought about another challenge. But my solution was to make the "long" side of the frames slightly smaller than standard 703 and keep the "short" side at a full 2' (on all frame sizes). This way, I only need to trim the 703 down on the "short" side, meaning less 703 scrap per 703 sheet than if the "long" side had to be trimmed. But ALSO, the 703 "scraps" that are cut off, if you cut everything neatly, these scraps can be lined up nicely inside a trap frame and USED, put together as one "full sheet"... thus not really "scraps" at all. I suspect I will use 99% of all my 703 if not 100%. If things go as planned, I will have used 100% of every bit of material I've purchased, including wood, 703, batting, felt, etc.




Below is a view of the rear side of the trap frames. They are held together solely by drywall screws, 1-5/8" long. No brackets are used or needed. Brackets can be expensive, I made sure to avoid them. Plus brackets alone are not nearly as strong as good bracing / supports (which can be made from wood much cheaper). The 1"X3" "support strips" I used do more than enough in terms of strengthening the frames, the frames are are 100% solid, zero flexing, stronger than they ever need to be. Drywall screws are not that strong alone, and pine is soft, but when supports are used like this, drywall screws into pine are more than adequate. It's all about design.

But I must mention, and this is important, all strips of wood here were cut with a good quality chop / miter saw for perfect right angle cuts. Good cuts allows things to fit together properly and tightly. If you were to cut these strips with any type of hand held saw, power or otherwise, the slight lack of precision with the cuts would mean the frames would likely not go together very well and you might be struggling, frames would want to sit off-kilter, would be loose and floppy in general, etc. If you do not have a good power chop saw (miter saw), and if you will be doing ANY type of carpentry work again, ever, just invest in one now, you'll be glad you did. I could not LIVE without my power chop / miter saw.




Quick shot of almost all the frames together, waiting for painting, stuffing, etc. There are over 30 frames in all. I actually hired a friend to help me screw all the pieces together because I figured it would take days, but surprisingly, one friend plus a few bottles of beer plus some good tunes in the boom box allowed me to get all these frames screwed together in under 3 hours... and yes, we had cordless screw guns, but we did pre-drill and counter-sink all holes for a neat look and to reduce splitting.

[666666]

Originally Posted by apadua

...The company that I work for moved buildings and were throwing out their cubicle partitions (3 floors worth)..I opened one up and it was OC703.. This is just one truck load.. I loaded up for almost 2 weeks and there was still some left over...

Holy CRAP! You DID win the lottery!!! Two weeks worth of full truckloads of 703?!?!?! Dude, just sell off that 703 and go buy a pre-built pre-treated state of the art recording studio and stop wasting time trying to build bass traps! Seriously, you must have collected quite a few thousand dollars worth of 703. That was a VERY lucky break! And I'm sure the people who let you take it had no idea of the value. Wow. It's always fun to hear stories like this. A friend of mine was once called to remove an old musty rug from an apartment, I think they paid him a few bucks to just take it away, turns out it was some ultra rare super special rug worth many thousands of dollars. I wonder when it will be MY TURN????!!!! (And no, please don't call me to remove your old musty rug for free.)

[apadua]

Originally Posted by 666666

Holy CRAP! You DID win the lottery!!! Two weeks worth of full truckloads of 703?!?!?! Dude, just sell off that 703 and go buy a pre-built pre-treated state of the art recording studio and stop wasting time trying to build bass traps! Seriously, you must have collected quite a few thousand dollars worth of 703. That was a VERY lucky break! And I'm sure the people who let you take it had no idea of the value. Wow. It's always fun to hear stories like this. A friend of mine was once called to remove an old musty rug from an apartment, I think they paid him a few bucks to just take it away, turns out it was some ultra rare super special rug worth many thousands of dollars. I wonder when it will be MY TURN????!!!! (And no, please don't call me to remove your old musty rug for free.)

Ha!... I actually sold a bunch locally and used the proceeds to picked up 6 GIK Tri-traps and 2 244's... I also hooked up one a couple of my friends... so I didn't make to much $$.. but Enough to pickup some a pair of SM81's, and upgrade my convertors (MOTU 828 to Lucid AD 9624 and DA9624)...

Sometimes I get lucky like that.. It is kinda of wierd... Have you ever heard or read that book the secret??? My girlfriend "made" me watch that movie with her right around the time I was looking into treating the room... So natrually I was obessing about how to build my traps color schemes etc... Then later that week I saw all those partions in the garage at my work... Kinda kweel....

[R_O]

Originally Posted by JouCalle

First post, great forum!
If I build my own porous absorber, what materials can I use to deflect high frequences?

On basstraps it's wise to install a low-end filter so it doesn't suck out all the high frequencies out of ye room. Add a sheet of plastic or a thin board of wood to accomplish such a filter.

[R_O]

Wow, 666666, thaz a lotta frames there!
I agree with you 100% on the mitersaw, buy a good quality saw and you'll be cutting great frames. I'm totally in love with mine

btw, why not leave an airgap behind the wool on purpose. It'll improve your low end trapping slightly

keep us posted, it sure looks promising!

[666666]

Originally Posted by R_O

Wow, 666666, thaz a lotta frames there! I agree with you 100% on the mitersaw, buy a good quality saw and you'll be cutting great frames. I'm totally in love with mine .... keep us posted, it sure looks promising!

Thanks!

btw, why not leave an airgap behind the wool on purpose. It'll improve your low end trapping slightly

Not sure if I fully understand your thought here but I'll just mention a few things:

The design of my trap includes a 0.75" air gap behind the 703 fiberglass. And I'm adding polyester batting to the top 0.75" to kill any reflections that might bounce off the plastic sheeting that will be wrapped around the 703.

In the room I'd space the traps away from the wall as opposed to screwing them directly to the wall, but the room is so small that I simply do not have the space to be able to do this. As it is, with the traps being 5.5" deep, placing them directly on the walls, I am losing a full 11" of width and length from the room, and losing 5.5" of ceiling height. I wish I had the room to hang them several inches out in front of the walls etc, but then I wouldn't be able to fit my gear in there! Yes, it's a SMALL room.

What I find interesting here, because small rooms can have such serious close-reflection issues, it seems that one needs the same amount or maybe even more bass trapping per square foot with a small room than with a larger room. Close-reflections can cause BIG problems (as I have observed first-hand) and MUST be eliminated in my opinion.

A friend of mine stopped by and saw all my trap frames and commented that my new room must be really huge for me to need all those traps... but in fact, the room is very small.

I plan to pretty much cover the entire ceiling with traps because the ceiling is low and the floor is a solid concrete slab. Bad enough I will have heavy reflections off the floor, but the last thing I want is standing waves between the floor and ceiling and general close reflections off the ceiling, etc. I want the ceiling to disappear... so I will cover it about 85% with my 5.5" traps. If I had more ceiling height I would have made them even thicker.

Walls too... will probably cover easily 80% of all wall surfaces with the traps. It's not that I specifically want a "dead" room, but close reflections cannot be tolerated. So it's gotta be "dead". I'd much rather have a dead room than one with wacky reflections and a horrible "small room sound". Once a "small room sound" gets on your tracks, it's there to stay no matter what you do, it's so critical in my opinion to make sure that when tracking, you're either in a good room or one that is well "trapped"... that is if you want to have any chance of yielding a pro-level production.

Considering my small room situation, it wasn't necessary for me to make all these frames. I could have maybe just screwed the 703 right to the walls and just hung blankets or curtains in front of it all, etc, would have saved a lot of time and work, but my feeling is that I hope to not be confined to this small room forever, hopefully things progress and I'll be able to get myself into a larger room in the not so distant future... thus by having my traps built nicely with frames etc, I will be able to move them very easily and quickly... and even now, if need be I could always just pull a few off the wall to bring to a remote location for recording, etc... makes the whole situation a lot more flexible.

Plus, the frames will ultimately allow me to mount the traps with very few holes into the walls. I will explain my ideas and post pics once I've hung the traps... but, in sum, my plan is to add three long "beams" to the ceiling, two brackets on each beam (total of nine bracket on ceiling and thus a total of hopefully just 9 holes in ceiling), from these three "beams" I will hang a whopping TEN of my 5.5" deep, 4'X2' traps. Nine small holes to hang ten huge traps, not bad I'd say... but the trap frames make this possible and reliable. I really don't want a lot of holes in my nice new sheetrock.

[Bouldy]

Hi all, fantastic thread!
I will hopefully be making some traps for my room from the designs here, but I am unable to get oc703 in my part of the world. I am trying to find a suitable alternative, so I have a question... Does OC703 have a facing (paper / wire mesh / foil) on one side?

Thanks Dave.

[embrionic]

Originally Posted by Bouldy

Does OC703 have a facing (paper / wire mesh / foil) on one side?

you can get OC703 faced or unfaced in my experience. You can also get products by other manufacturers (mansville etc) that are similar densities in faced or unfaced, and are often cheaper.

comes with paper or foil, never seen wire mesh.

[Bouldy]

Originally Posted by embrionic

you can get OC703 faced or unfaced in my experience. You can also get products by other manufacturers (mansville etc) that are similar densities in faced or unfaced, and are often cheaper.

comes with paper or foil, never seen wire mesh.

Thanks, have investigated further and found a product from the same supplier without mesh, which is supplied faced or unfaced which should do the trick!

[embrionic]

Originally Posted by Bouldy

found a product from the same supplier without mesh, which is supplied faced or unfaced which should do the trick!

check the density from the manufacturers specs. The density of the substance is a key component in its ability to absorb specific frequencies and work effectively in whatever DIY design you choose. You can go with less density, but you may need more depth to achieve the same results (thicker traps) . The reason you have seen "mesh" in some designs is it is often a less dense insulation (the pink stuff) packed into a frame with mesh to contain the fluffy stuff.

703 is 3 pcf and 705 is 6 pcf.

good luck.

[Bouldy]

I think the one with mesh was meant for wrapping around pipes, but the one I am looking at now has a density of 100Kg/m3
Not sure exactly how that equates non metrically but thought it was in the ballpark.

Dave

[JouCalle]

Originally Posted by R_O

On basstraps it's wise to install a low-end filter so it doesn't suck out all the high frequencies out of ye room. Add a sheet of plastic or a thin board of wood to accomplish such a filter.

OK, but are you SURE? Doesn't a porous absorber work by braking the air-molecules that go through? With plastic in front, do anything really go through or does it work like a membrane?

Could anyone explain the physics? Thanks!

[666666]

Originally Posted by JouCalle

OK, but are you SURE? Doesn't a porous absorber work by braking the air-molecules that go through? With plastic in front, do anything really go through or does it work like a membrane?
Could anyone explain the physics? Thanks!

I believe Ethan Winer explained this not too long ago within another thread. I'll look around for it and link it here if I can find it.

I was concerned about the same issue, wasn't sure if the entire thickness of the trap would need to be "free-flowing" with respect to AIR movement in order to be effective, but I was assured this is not the case. OF course if you have a sheet of plastic as your final finished layer, you are going to get a lot of upper frequency reflection off that, but if you have some degree of absorption in front of the plastic, then the plastic should not have any adverse effect on the trap... at least how I understand it based on what the knowledgeable people of this forum have explained.

In my opinion, you do not really need to worry about building reflection into your bass traps, if you need a little extra reflection, just leave a certain degree of the already reflective surfaces in the room uncovered. Or add some separate diffusors, etc.

As I may have mentioned in another post somewhere, since my room is so small, I AM pretty much covering almost all surfaces with bass traps because I do not want ANY close reflections happening. Will the room sound too dead? Maybe. But too dead is better than nasty ugly close reflections with resulting phase gremlins and other weirdness.

BUT, if I do find it way too dead to the point of ridiculousness, I may just try nailing some thin wood strips on the front of the traps, at different angles, etc... this will add a bit of reflectivity and a theoretical tiny bit of diffusion (if I have a bunch of different angles happening). What I like about this idea, you can add wood strips little by little until you gain just the right amount of reflectivity. And adding scattered strips also will yield a scattered reflectivity which is likely better than having one huge flat reflective surface in one spot... with a scattered "grid" of reflectors, I'd think the chance of having a nasty close refection issue in a given spot would be way less than otherwise.

[666666]

Originally Posted by 666666

I believe Ethan Winer explained this not too long ago within another thread. I'll look around for it and link it here if I can find it....

Ok, here:

http://www.gearslutz.com/board/4007791-post3.html

[JouCalle]

Thanks! And having wood slats sounds brilliant!

Maybe this is how it works:

The plastic (reflector) moves along with lower frequences but cannot move as fast as high f so they bounce of, maybe?

I need to understand this! :P

[R_O]

It's just a matter of Mass, if you will. Mass will isolate sound. The denser the mass (heavier) the more it'll isolate in the low frequency range. So basically, by adding a sheet of plastic (not too much mass) you'll isolate higher frequencies a bit from the absorbing material. Adding more mass will isolate it better and even lower in frequency. The energy gets reflected back into the room. Low frequency, as you should know by know, is harder to "isolate", so plastic will do squad in that case; resulting in a bass-only-absorber (well, sorta)

[666666]

Originally Posted by JouCalle

The plastic (reflector) moves along with lower frequences but cannot move as fast as high f so they bounce of, maybe?

I need to understand this! :P

I'm no scientist, but...

Just imagine a large sheet of super thin plastic only (like plastic food wrap), hanging in front of a door opening. Regardless of how it may vibrate, I don't see how it could effectively absorb low-end. If it does, it would be such a minimal amount that it would not be audibly detectable.

But since the plastic does have a bit of mass technically (very small amount), it does reflect something... the very highest of highs... whatever super short frequency wave-length it's small mass / thickness is able to interrupt. This is something that CAN be detected by ear... I know because I've tried it. If you cover an open room frame with plastic only and step inside, you WILL hear very high frequency reflections.

As far as using plastic in a bass trap where the plastic is covered with at least 3/4" of fluffy batting material, I don't see how the plastic will reflect anything because, let's say the plastic would have reflected 10kHz and up, the 3/4" batting would absorb the 10kHz and up before it even hit the plastic, and everything below 10kHz will just go right through the batting and plastic like it wasn't even there... the ultra thin low mass plastic cannot interrupt longer waves.

Then just make sure to have some good dense absorption material behind the batting and plastic to eat up the longer waves / lower frequencies.

Anyway, this is all just per my understanding, I am not a scientist and am not proclaiming that any of this is 100% correct. I am however building some custom traps based on these ideas that I will soon be putting to the test and will report back. I may not do any scientific measuring, but will test musically... and if it SOUNDS good, it IS good.

[Classic]

On building SuperChunk style bass traps in the corners with the triangles floor to ceiling, are these triangles flush against the wall?