Acoustic Treatment Proposal - What do you think?

[Electric Sugar]

I'm getting some budget acoustic treatment done in my little home project studio. It's a tiny room (the only one available unfortunately) and it isn't ideal, but I'm pretty sure I can make some pretty big improvements on it.

Obviously, my main concern was bass traps. I have 3 corners available for those. I also want something to reduce the room reflections and flutter echo, because I also use this room to record vocals (not ideal I know, but my budget is low).

A big problem is, I'm not allowed to attach anything to the walls, as it's rented accomodation.

A mate of mine, who certainly knows his stuff when it comes to custom engineering, prototyping, physics, all round mad science, has come up with a solution, based on my specifications and a bit of research we've both done into budget studios. I'd like you guys to have a look over it and see if you think there are any changes you would make to it.

I'm well aware that it isn't ever going to sound perfect, but I'd like to think this small budget custom project would make a difference to what the room sounds like, particularly for listening/mixing.

Here is the proposal:

[Electric Sugar]

Brief:

acoustic treatment of a 3m squared room. One corner is doubled by the presence of pipe boxing that runs floor to ceiling of approximately 200mm. As such it will function as a corner reflector for frequencies of 1700 Hz approx and up. The remaining three corners are good for 115 Hz or so and up.

Customer requirements include bass traps, reverb deadening and no permanent fixtures in the walls as the premises are rented. Customer also requires the work done on a budget.

NOTE: all of the frequency calculations are very rough, and based on assuming 20 Celsius in the room and a speed of sound of 343 M/s. The warmer your room gets, the better the reverb deadening works as the speed of sound gets faster the wavelength at a given frequency gets longer.

Solution:

Bass traps. The ideal solution is acoustic foam bass traps, floor to ceiling, in all four corners. That would work out at over £200 per corner at current prices. However, with 12m of plain cloth plus one bag of 150mm ISOWOOL acoustic and insulating wool, bass traps for all corners can be made at a material cost of just under £90. These 'sausages' of mineral wool, hung in the corners of the room, are almost as good as acoustic foam traps but a fraction of the price.

Reverb deadening: I have 10mm acoustic foam in 2.4m by 1.2m sheets in stock as surplus from a previous job which I can supply for £7 each. One wall of the room is occupied by the window, on which the curtains will function as a deadening material. (Stephen, you can pick up ready made heavy velvet curtains for not much money, quite long. They'll do the job better than the light cotton ones you've got, and Lorraine can run you up liners for them that'll make them even better.) The minimum needed will be four sheets, one for each of the other walls and one for the ceiling. Divided lengthways they'll ensure that the widest piece of wall or ceiing will be about 80 cm, giving you immediate deadening on any frequency at or below about 400Hz and shortening the reverb time of frequencies above that markedly. Obviously you don't want the room to approach perfect anechoic condition, a little room character is desirable. If you want more foam, I've got a whole bale of it if you want to increase the coverage.

Mounting: because you can't have permanent fixings, I propose to build a timber frame inside the room using 2 by 1 slate battens held together with roofing bolts so it can be disassembled. The frame will go around the ceiing with supports in the corners, with a few diagonal corner braces for stability. The timber is about 35p a metre ex VAT.

Total cost: it'll be about a day's work for me to build the frames while you make the bass traps out of the material I'll deliver (it's dead easy, trust me!) and I propose to charge you £100 mates' rates for that and all the work in sourcing the stuff.

Materials: bass traps, £90
Foam: £28
Timber: £15 (about, I've not done a detailed calculation as to the amount I'll need for the bracings)
Bolts, hooks and eyelets for hanging the foam and basstraps: £5 total.
Labour: £100

[Electric Sugar]

Anyone? I'm eager to get started with this.

[Glenn Kuras]

These 'sausages' of mineral wool, hung in the corners of the room, are almost as good as acoustic foam traps but a fraction of the price.

Actually the mineral wool will do better then foam.

The guys thoughts don't seem all that bad but why not just build (or buy) all the acoustic panels (and bass traps) and put them on stands? It is going to work better and when it comes time to move you just pack up and go.

[Electric Sugar]

Space in the room basically. It's so small, stands would take up precious room. And also it means that I can get something on the ceiling, which seems to be the worst area for the flutter echo.

Thanks for taking the time to read it.

[SaSi_SiDi]

If you can't mount anything on walls - but can mount the hanging frame from the ceiling - then mounting restriction isn't causing any harm.

Best approoach for a bass trap is to have a thick (10cm or thicker) block of mineral wool at a distance of 10cm from the wall. The three corners can have these traps, which can be custom made for the room height and mounted on the ceiling frame.

You can mount wall traps in the same way, instead of mounting them on the wall you just hang them from the ceiling "railing". You could use as much of the free walls as possible or financially feasible.

The velvet curtain for the window isn't a bad idea. You need to ensure that the cloth has as folding as possible. And be mounted as far as possible from the window itself.

Since you can mount on the ceiling, you could also consider a "cloud" construction, basically a bass trap for the ceiling. That would create quite a good percentage of trapping for the wall/ceiling surface.

[Electric Sugar]

The frame is what keeps the foam on the ceiling. The frame follows all the edges of the room, so I can use it to hang stuff over the walls and to go from one side to another over the ceiling.

Cheers for the comment on the curtains, I'll make sure my seamstress makes them as baggy as possible.

[transnove]

Originally Posted by SaSi_SiDi

If you can't mount anything on walls - but can mount the hanging frame from the ceiling - then mounting restriction isn't causing any harm.

The hanging frame doesn't hang from the ceiling: to do this I'll be putting uprights in all four corners. It's not a difficult bit of joinery but it is laborious.

Originally Posted by Glenn Kuras

Actually the mineral wool will do better then foam.

I'm interested to hear that the mineral wool bass traps will work better than foam ones. If so, why does anyone buy foam ones? Mineral wool is, by comparison, incredibly cheap, and even buying the cloth to cover it up with so you don't itch yourself to death (the makers of the brand we'll be using advertise it with a lady handling it while wearing a bikini, to try and crack on it's non-itchy, THEY LIE) brings it in at a fraction the price of foam bass traps. Enough wool of 150mm thickness to do all four corners floor to ceiling is just over £20 from the builders' merchant I use.

Is there experimental data to make a comparison anywhere online?

[Ethan Winer]

Originally Posted by transnove

Is there experimental data to make a comparison anywhere online?

Foam works okay if it's large and thick. The main problem with corner foam is the way it's produced. The wedges are typical much smaller than 2x4 by 3-to-6 inches panels made of rigid fiberglass and rock wool. The main problem with sculpted foam panels is that the sculpting removes literally half of the material. If you take two pieces of 2-inch thick foam and place them face to face, you now have something that's actually two inches thick. So most foam needs to be twice as thick to work to as low a frequency as rigid fiberglass. But as a raw material, real acoustic foam like Auralex and Sonex is not as bad as you may read in web forums.

--Ethan

[Glenn Kuras]

I'm interested to hear that the mineral wool bass traps will work better than foam ones. If so, why does anyone buy foam ones? Mineral wool is, by comparison, incredibly cheap, and even buying the cloth to cover it up with so you don't itch yourself to death brings it in at a fraction the price of foam bass traps. Enough wool of 150mm thickness to do all four corners floor to ceiling is just over £20 from the builders' merchant I use.

Is there experimental data to make a comparison anywhere online?

Ethan gave you the right answer.

(the makers of the brand we'll be using advertise it with a lady handling it while wearing a bikini, to try and crack on it's non-itchy, THEY LIE)

I think the only time I see that is for acoustic cotton, which will not make you itch.

[MonkeyGang]

Originally Posted by Electric Sugar

Brief:

acoustic treatment of a 3m squared room....

Do I assume right You rent a 3sqm place? Or...?