How I built my bass traps...

[PaulP]

We've had two members build some in the last month or so. Searching on
panel traps should find them. There hasn't been much in the way of feedback
from them though, which I'd be interested in.

Paul P

[Lonely Raven]

How are that style of trap different? Just the frame, or what?

[takman]

Raven....good work man....looks really nice thumbsup

[Lonely Raven]

Originally Posted by takman

Raven....good work man....looks really nice thumbsup

Thanks! More to come!

I fixed the second photo. I didn't realize I copied the first one twice.

After talking with Ron Sauro about acoustics, I might be changing my designs a little bit. Instead of 4' X 4' panels, I think I'm going to be making 1' X 5' strips as they are more effective.

[ajbianco]

Originally Posted by Glenn Kuras

Well on a 4x2 4" panel it would give you 50% more exposed area if the sides are open.. 6"? well, check my numbers but that would be 75% more exposed would it not?

Nice DYI dude! ... You may want to think about putting some FRK on the fronts. This will help with a little more low end and also keep the room from going "DEAD" on the high end.

Glenn

for this statement to be correct, your are implying that a thin strip of aluminium will somehow increase low end absorption and decrease high end absorption.

what happens..... does the soft insulation allow the metal face to deflect low end, thus absorbing it in the process, but not do this at the high end?

to be honest i'm not convinced about this whole claim yet....

[johndykstra]

Originally Posted by ajbianco

for this statement to be correct, your are implying that a thin strip of aluminium will somehow increase low end absorption and decrease high end absorption.

what happens..... does the soft insulation allow the metal face to deflect low end, thus absorbing it in the process, but not do this at the high end?

to be honest i'm not convinced about this whole claim yet....

The theory is that high frequencies will be reflected by the non-porous surface of the foil. Being that the foil, when struck by lower frequencies, will vibrate as a solid "mass"; it effects the insulation on a grander scale.

Someone will be along shortly with a link to proven test results I'm sure.

[JR1125]

Inspiring thread, really is

[mobilemozart]

Originally Posted by Pretension

For all of you that are reading this forum and wondering whether to build your own acoustic treatment whether it be bass traps or otherwise you should check out this video that I made.



Hopefully you should be able to hear the difference that it has made to my studio. Enjoy!

Great DIY work, great video, thanks for posting this!

[Obitheincredible]

Great thread!

[rashman]

Hi guys. Here is a quick report of building my traps – 15 units total. The wooden boxes were designed by me but built by local carpenter. The rest was my work :-)

[drumphil]

Rashman, is that a clay Tombak resting on the floor in the last picture? The Tombak is one of my favorite percussion instruments, I wish I could play it like the Iranian masters!
all the best.

[rashman]

Originally Posted by drumphil

Rashman, is that a clay Tombak resting on the floor in the last picture? The Tombak is one of my favorite percussion instruments, I wish I could play it like the Iranian masters!
all the best.

Yes drumphil. That’s a giant clay tombak played in the Iranian traditional sport arenas. I also love Tombak. It’s a very unique Persian instrument. I’m recording an album right now using tumbak as the main percussion :-)

[pkarpiozo]

Here is my bass trap and they are up for sale as well.

http://www.gearslutz.com/board/gearslutz-secondhand-gear-classifieds/462296-eu-bass-traps-wideband-abs-bought-never-used.html

[rashman]

Hi guys. I built four more traps, chunk style. Just couldn't resist not show :-)

[PaulP]

Originally Posted by rashman

Hi guys. I built four more traps, chunk style. Just couldn't resist not show :-)

Nice work thumbsup

Paul P

[SaSi_SiDi]

I have been meaning to post pictures of my first attempt at a bass trap for some weeks now. So here it is.

The aim is to build two corner traps for the front corners of the room. Almost floor to ceiling (2.50m high) and about 1.2m wide.

I started building a framework for the trap using horizontal planks in the desired shape for the trap and two vertical edges. I used scrap pieces of vinyl covered chipboard that were leftovers from the house construction.

The first two pictures attached show the horizontal pieces and what they are made of.

[SaSi_SiDi]

Next few pictures show how the horizontal pieces are mounted on one of the vertical edges.
The distance between the horizontal planks is 60cm (2ft) following the width of the rockwool. The trap is going to be 10cm (4") thick and covered with fabric on both sides.

[SaSi_SiDi]

Next few pics show progress as the rear side fabric was stapled in place. I tried to stretch the fabric as much as possible.

Then inserted two layers of rockwool in each "compartment. I had to cut the rockwool slabs and I used a flat saw for that.

It took some effort to mate the edges of the rockwool slabs at the angled side. I had to work on that as these sides were going to be visible from the front.

[PaulP]

Nice work, I look forward to seeing these in place.

What density rockwool are you using ?

Paul P

[SaSi_SiDi]

Originally Posted by PaulP

Nice work, I look forward to seeing these in place.

What density rockwool are you using ?

Paul P

45kg/m3 is the one I bought. I also found 100kg/m3 but from what I've read it might have been a bit too much. It appears I got a real deal on the rockwool as I paid 60 euro (~$90) for 3 packs of 8 panels each (2'x4'x2").

I realized I haven't yet taken a pic of the panel in place. I am waiting for the camera batteries to recharge and will take a pic of the panel in place.

I consider this trap to be a failure in terms of design. Although it made a very audible difference now that it's in place.

Version 2 will be made in pieces, each 60cm height as a separate panel. This huge "thing" was impossible to handle and mount on hidden anchors. I thought I was taking a shortcut by making a single panel but the weight and size are both too much for even two strong men to to accurately handle.

[pkarpiozo]

Originally Posted by SaSi_SiDi

45kg/m3 is the one I bought. I also found 100kg/m3 but from what I've read it might have been a bit too much.

I think it wouldn't hurt to have few 100kg/m3 panels as well in your place.
They will work better in lower freq than 45kg/m3.

[johndykstra]

Originally Posted by SaSi_SiDi

Next few pics show progress as the rear side fabric was stapled in place. I tried to stretch the fabric as much as possible.

Then inserted two layers of rockwool in each "compartment. I had to cut the rockwool slabs and I used a flat saw for that.

It took some effort to mate the edges of the rockwool slabs at the angled side. I had to work on that as these sides were going to be visible from the front.

may I suggest using a layer of batting before you put down the finish fabric. It will hide some of the sins in the rockwool.

[SynthLine09]

on average, how much would yall guess it would cost to build a pair of bass traps for a smallish medium sized room?

[SaSi_SiDi]

Originally Posted by dykstraster@gmai

may I suggest using a layer of batting before you put down the finish fabric. It will hide some of the sins in the rockwool.

Version 2 of the corner trap will have two important modifications / improvements:
1. It will be made in slices, 2ft high each, for ease of handling. (to make it feasible for me to lift the damn thing and mount it on the wall).
2. I will use some sort of facing at the front side so that rockwool mating is concealed and also high frequency absorbtion is decreased.

I am currecntly considering to combine this with a limb mass hanging behind the trap. As soon as I can figure out the mounting details I will start the build and also do measurements.

[SaSi_SiDi]

Originally Posted by SynthLine09

on average, how much would yall guess it would cost to build a pair of bass traps for a smallish medium sized room?

The size of the room makes no difference on the size of a trap. All rooms can use large traps. Small rooms probably more.

The bass trap cost is made up of absorbing material (glass or rock wool), paneling planks, fabric and effort. To that add a few pieces of joining and mounting tools and screws.

For a 4" trap, it cost me around 5 euros ($9) for the rockwool to do a 2x4ft surface. Wood planks (chipboard or mdf) should cost <$10 for the frame and cloth could be the most expensive item at $10~15 for a frame (both faces).

[SynthLine09]

Thanks so much! seems like a much more economical option than purchasing them...

[johndykstra]

Originally Posted by SaSi_SiDi

I am currecntly considering to combine this with a limb mass hanging behind the trap. As soon as I can figure out the mounting details I will start the build and also do measurements.

Have you looked at this thread:

Bass Traps - Diaphragmatic resonators & Limp Mass

I'm in a similar boat. Just trying to hammer out the details. In the above thread you'll find a link to Primacoustic's page. Scroll down, there's photo of them installing the vinyl in a trap. If you don't mind, if you find a good mounting method, would you mind posting it in that thread?

[PaulP]

Originally Posted by dykstraster@gmai

I'm in a similar boat. Just trying to hammer out the details. In the above thread you'll find a link to Primacoustic's page. Scroll down, there's photo of them installing the vinyl in a trap. If you don't mind, if you find a good mounting method, would you mind posting it in that thread?

Here's the link : Primacoustic - Acoustical Solutions.

The wooden strips appear to be screwed to the sides. I wonder what effect
different tensions would cause, surely it must affect the resonant frequency.
Or just how limp is 'limp' ?

Looks like a great model for a corner absorber.

Paul P

[SaSi_SiDi]

The primacoustic design is based around a 3" thick absorber panel mounted 5" away from the wall for a total thickness of 8" (as far as I understood the explanation and diagram).

The limb mass is suspended in the back of the absorber panel allowed to freely vibrate. That means that it should have a clearance from any surface (either the absorber panel or the back of the cavity) of 1" or so.

Now, as we all know, the wave velocity is higher as we move away from rigid boundaries, so the sheet is best suspended as close to the absorber panel as possible. At least that's how I understand it.

Regarding mounting, I am considering to use two pieces of 30x40mm hardwood planks and sandwitch the bitumen sheet between them. Then mount the sandwitch to the wall.

I am thinking of two scenarios. First scenario is for a corner trap and in such a case the sheet needs to hang at an angle to the wall-wall corner. My design for the corner traps calls for a 30 degree angle, so the bitumen sheet needs to hang at this angle behind the trap. Obviously I need to find a way to mount the wood planks at the two ends (angle cut to mate with the wall).

I am not sure if it's feasible to hang a single 250cm (8ft) long bitumen sheet. It has to do with the weight. The 10meter long roll is a bitch to lift and carry but manageable for me. I haven't weighed it but I am guessing 35~40kg (70~80lbs), so I am looking at a 7~12kg weight for the sheet plus wood support. It's easy to lift 10kg but not that easy to make precision mating with a 10kg inflexible sheet 250cm long. I may have to split it into parts.

I am also thinking that if I make a single sheet 250cm long, then the weight of the sheet itself will make the top part of it tension to the point that it defeats the point of "freely vibrate". I also need to think about ageing and the weight might elongate the sheet and deform it - perhaps to the point of failure. I have never worked with bitumen sheets before freely hanging. They are usually secured and glued in place.

So, the alternative is perhaps to combine the sheet in the back of each corner trap module. I am planing to make the floor to ceiling trap in parts, each module being 2ft high. Perhaps I need to re-design the top part of the frame so that the bitumen sheet can hang from there in the back of the trap.

[PaulP]

Originally Posted by SaSi_SiDi

The primacoustic design is based around a 3" thick absorber panel mounted 5" away from the wall for a total thickness of 8" (as far as I understood the explanation and diagram).

The limb mass is suspended in the back of the absorber panel allowed to freely vibrate. That means that it should have a clearance from any surface (either the absorber panel or the back of the cavity) of 1" or so.

In the Primacoustic corner trap the limp mass isn't exactly hung, as in hanging
from a horizontal support at the top, but tied all along both sides to strips of
wood that are screwed to the sides of the enclosure. So it's not just hanging
free. Depending on how tight the fit is, the limp mass will be more or less
taut.

I can't find how the limp mass is attached in the other absorbers but I don't
see why it wouldn't be the same.

Paul P