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What type of material to use for bass traps and acoustic panels?

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What type of material to use for bass traps and acoustic panels?

Postby samuk » Mon May 06, 2019 12:16 pm

Hi everyone,


Apologies for the long post, and I’m aware this is an often discussed issue but I’ve become confused and would appreciate any advice.

I’m intending to build bass traps for my room and also acoustic panels that would absorb mid/high frequencies. But I’m unsure as to whether my thinking is right on what type of material I need and what specific material, density and depth to use. Specifically I want to know what type of Rockwool or similar material I should get for the bass traps and for the acoustic panels.

In terms of what’s commercially available, the Gikacoustics 244 bass trap and their Monster bass traps are the kind of thing I’m aiming to make, and the 242 Acoustic panel similar to what I’m aiming for with the acoustic panels for mid/high frequencies.

My room is fairly small. The measurements are:

273cm (width) x 363cm (length) x 294cm (height) (at highest point - sloping ceiling starts at 59cm from window side, goes up to a beam at 259cm - then the highest part on door side is 294cm))

I’ll be using it for both tracking and mixing.


BASS TRAPS -

As far as I understand it the material that should be used for bass traps needs to be deep and of lower density.

The depth is needed because low frequencies have long wavelengths - so the traps need to be physically deep to absorb them.

Lower density is also better for bass traps - as far as I can tell from my online reading - as it allows more space between the fibres for the sound waves to pass through and be absorbed by the fibres as they introduce friction to the moving air and reduce it’s velocity. The denser material can also reflect more of the high frequencies back into the room which can be problematic.

The exception to this would be if you only had space for thin traps, where higher density might help.

I have read that as a result of these factors it’s better to use what an American site called ‘pink fluffy stuff’ - or low density glass wool loft insulation (usually grey or yellow in the UK).
However, this is supposed to be more effective when unwrapped, and as a result would take up a lot of space in an already small room. So I was thinking of using acoustic slabs as these also have the advantage of preserving their shape by being more rigid and so being easier to fit into a wooden frame or just freestanding. The ease of using them and the smaller footprint makes them attractive.


THE ACOUSTIC PANELS FOR MID/HIGH FREQUENCY ABSORPTION -

These are to treat early reflection points, flutter echo and general decay. I’ve read that depth is also required here, but they seem to have less depth than the bass traps - presumably because of the shorter wavelengths of those frequencies?

I am unsure about what density and thickness/depth of material/Rockwool to use for them.


MY QUESTIONS -

Can anyone give me any ideas - preferably as specific as possible - on:

• What density (in kg/m3) glass wool loft insulation would work well in bass traps?

• What would be a minimum depth and a desirable depth of the glass wool loft insulation in a small room for bass traps?

• Are there any specific brands that are better than others?


Thanks in advance :)
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Re: What type of material to use for bass traps and acoustic panels?

Postby Sam Spoons » Mon May 06, 2019 12:29 pm

I used Rockwool RW3 50mm thick for my broadband absorbers and bass traps. Cut and stacked in the latter and around 8" deep. I wouldn't worry too much about the minutiae of it, RW3 is 60 kg/m3 (and usually considered the best compromise) and is pretty easy to work with.

Build your bass traps as deep as the space in the room allows and remember you can use any of the corners not just the vertical ones.
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Re: What type of material to use for bass traps and acoustic panels?

Postby Music Wolf » Mon May 06, 2019 4:23 pm

RW3. I'm using 1200 x 600mm panels (4' x 2' in old money), 100mm thick. RW3 is usually sold in packs with a total depth of 400mm so 4 x 100mm, 8 x 50mm etc. I have a room with dimensions similar to those of yours. I have the mirror points (walls & ceiling) treated with 100mm thick panels suspended a further 100mm from the wall. Front corners are treated with 'super chunks' made by cutting slabs into 4 triangles and stacking. Cara fabric for best effect.

The only application I could see for 'pink fluffy stuff' would be if you were to place an RW3 panel across a corner and use the pink stuff to fill the space behind. Better than an air gap but not as good as a 'super chunk'. Since the Rockwool is only part of the cost, and these traps take time and effort to build, I personally would just buy enough RW3 to fill the corner.
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Re: What type of material to use for bass traps and acoustic panels?

Postby blinddrew » Mon May 06, 2019 4:36 pm

This ^^^ is the approach I hope to be taking later this year. :)
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Re: What type of material to use for bass traps and acoustic panels?

Postby Luke W » Mon May 06, 2019 5:11 pm

Music Wolf wrote:RW3. I'm using 1200 x 600mm panels (4' x 2' in old money), 100mm thick. RW3 is usually sold in packs with a total depth of 400mm so 4 x 100mm, 8 x 50mm etc. I have a room with dimensions similar to those of yours. I have the mirror points (walls & ceiling) treated with 100mm thick panels suspended a further 100mm from the wall. Front corners are treated with 'super chunks' made by cutting slabs into 4 triangles and stacking. Cara fabric for best effect.

The only application I could see for 'pink fluffy stuff' would be if you were to place an RW3 panel across a corner and use the pink stuff to fill the space behind. Better than an air gap but not as good as a 'super chunk'. Since the Rockwool is only part of the cost, and these traps take time and effort to build, I personally would just buy enough RW3 to fill the corner.

:thumbup: Definitely, I went for the stacked triangles approach for the corners of my room where I could and it's done a good job. If you can, it's worth trying to get the Rockwool from a building supplier, I got it a fair amount cheaper than studio specific suppliers were selling it for.

Sam's point about wall/ceiling corners is a good one as well, my current setup is based in an attic room dormer so there were some interesting shapes to work around, but one of the most effective parts of the build was sloping the ceiling down towards the window the setup faces out of.

I've got a lot of pictures of my build from start to finish, I'm by no means an expert when it comes to acoustics and a lot was learnt along the way, but I'll gladly get them up on here if they're of any use to anyone.
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Re: What type of material to use for bass traps and acoustic panels?

Postby blinddrew » Mon May 06, 2019 5:51 pm

This is cheapest place I've found for rockwool so far - if anyone has seen anything cheaper please let me know! :)
https://www.just-insulation.com/mineral ... 5-rw6.html
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Re: What type of material to use for bass traps and acoustic panels?

Postby samuk » Tue May 07, 2019 1:29 pm

Thanks very much for your replies everyone! Much appreciated. Conflicting opinions had left me very confused.

So RW3 it is, and I’m intending to do the superchunks type traps in the corners now. There’s one corner that this might not be possible for as the door is close to it, but for that I might just do a free-standing panel style bass trap that I can move when I need to use the door.

Luke W - love to see your pictures if you can put them up. I’m a novice at acoustic treatment and DIY so anything I could follow would be great.

Thanks again - you’ve brought me a major step closer to completion :))
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Re: What type of material to use for bass traps and acoustic panels?

Postby Mixedup » Tue May 07, 2019 1:36 pm

You can usually shave a wee bit more bit off that if you're buying a full pallet — which depending on your room size and how 'belt n braces' your approach to treating it is may or may not be the case — though which merchant is cheapest varies from week to week. Just do a Google search on, for example, Rockwool RW3 pallet.

(Thing is, some of those merchants aree a bit hit and miss on delivery dates... they just order pallets direct from the distributor and pass on a bit of their bulk saving, shaving a commission off as they do so. They never actually have it in stock and never handle it... Which is fine if you're having it sent to your home and don't have workmen waiting on it, but less so if you need it on site at a specific time!)
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Re: What type of material to use for bass traps and acoustic panels?

Postby Mixedup » Tue May 07, 2019 1:38 pm

Btw, I'll bow to those with greater expertise than me, but one practical advantage of RW3 over RWA45 is that it's slightly more rigid... ie it flops less, cuts easily with a large-toothed breadknife, and needs less bracing to hold it in place. Relatively, the heavier 100kg/m3 stuff which is more rigid still tends to sound a bit dull and boomy though... presumably it's reflecting more? I find RW3 a happy medium...
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Re: What type of material to use for bass traps and acoustic panels?

Postby Sam Spoons » Tue May 07, 2019 2:07 pm

My total cost for timber, corner brackets, Cara fabric, RW3 etc was around £300 and I built 10 panels, 5 off 1200 x 600, 2 off 900 x 600, 2 corner super chunks and one 8" deep super chunk type panel behind the monitors.

Image
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Re: What type of material to use for bass traps and acoustic panels?

Postby Luke W » Tue May 07, 2019 2:28 pm

Nice work, Sam. :thumbup: Looks like we went for the same colour fabric!

I didn't keep count of the total cost of mine, it was somewhere around the £450 mark, but that was including building a new desk as well. Without a doubt the best money I've spent studio-wise, I know it gets said again and again but the difference the treatment makes is like night and day.
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Re: What type of material to use for bass traps and acoustic panels?

Postby samuk » Tue May 07, 2019 3:18 pm

Your room looks great Sam! Bigger than mine but very close to what I’m aiming for.

Very cheap too. Gikacoustics recommended treatment costing £700, but I thought it would be cheaper to do it myself and having looked at the cost of RW3 that’s definitely the case. Also, I thought it would be good to learn to do it myself to make adding any future treatment easier and cheaper.

I’d been intending to do acoustic treatment, but recently got a Brauner Phanthera mic, and while it’s an outstanding mic it picks up everything and is very unforgiving on the room.
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Re: What type of material to use for bass traps and acoustic panels?

Postby Sam Spoons » Tue May 07, 2019 4:37 pm

Acoustic treatment is the best studio upgrade you can do to an untreated room. I worked out that I saved around 40% over GIK prices (which, actually, makes Gik stuff very good value). The best choice I made WRT materials was to use Cara fabric, it even makes my DIY efforts look good.
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Re: What type of material to use for bass traps and acoustic panels?

Postby Luke W » Tue May 07, 2019 4:43 pm

Sam Spoons wrote:The best choice I made WRT materials was to use Cara fabric, it even makes my DIY efforts look good.

Agreed, it seems like it's almost harder to make a bad job with it, lovely stuff to work with.
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Re: What type of material to use for bass traps and acoustic panels?

Postby Martin Walker » Tue May 07, 2019 7:57 pm

Mixedup wrote:Btw, I'll bow to those with greater expertise than me, but one practical advantage of RW3 over RWA45 is that it's slightly more rigid... ie it flops less, cuts easily with a large-toothed breadknife, and needs less bracing to hold it in place. Relatively, the heavier 100kg/m3 stuff which is more rigid still tends to sound a bit dull and boomy though... presumably it's reflecting more? I find RW3 a happy medium...

Agreed - I bought RWA45 for my biggest traps, and it worked well, if I repeated the process I'd go for RW3 now to make the framing/finishing a little less 'floppy' :beamup:

60Kg/m3 does seem to be the happy medium between floppy and expensive ;)


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