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full acoustic treatment in a small room

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full acoustic treatment in a small room

Postby Bob Moose » Sun Nov 18, 2012 5:31 pm

Hello,

I would like to work as a composer and producer but my current room (actually also my living room) is really bad.
Now I have the opportunity to work in a dedicated room that is about 4.6 x 3.3 x 2.3 m (LxWxH). Like in all small rooms a serious acoustic treatment is necessary.
The good news is I can do everything I want there, for example building a "room inside the room" solid frame for supporting the acoustic treatment if this is necessary. Also, there won't be much gear: everything will be installed inside the speaker circle (radius = 100-120 cm). So quite a lot of space is left for the acoustic treatment, especially in the corners, but even along the walls.
Currently I have no idea if I will DIY all this, or hire a professional team, or both.

I am new to acoustic treatment but last week I read many pages about it, most of which were written by Paul White, Hugh Robjohns, Martin Walker, Ethan Winer, Peter d'Antonio, and the GIK team. Thanks for these great articles by the way.

The most important thing to do is improving the low frequency response. Bass traps that use both rockwool and barrier mats (limp masses) seem to give the best results for small rooms, and they do not look too hard to build. But where should I put the barrier mat? Sometimes it is installed between the rockwool and the room, sometimes between the rockwool and the wall; I imagined using several mats in parallel too, or alternating slices of rockwool and mat.

Also, "there cannot be too much bass trapping in a small room", but "covering the whole room with traps that also absorb the medium and high frequencies is not recommended".
So isn't it better to build bass traps that do not affect the mid-high frequencies? This way I could install enough bass traps without making the room sound too dead.
Perhaps it is possible to cover all the bass traps with a "frequency crossover" material that reflects the mid-high frequencies back to the room, and let the low frequencies enter the trap (I'm not sure, but I guess thin plywood could do this; or perhaps the barrier mat if it is mounted room-side).

I also thought about installing a giant bass trap system on all the walls, the corners and the ceiling, and then covering 50% of the walls with vertical pieces of wood (a kind of binary amplitude diffusor), perhaps with a proper diffusor on the rear wall.

But maybe having large bass traps in all 12 corners is enough, or adding two times more only makes a very small difference, well I have no idea actually.

Bass trapping is not the only thing to do but I must decide it before the remaining. Which solution would you recommend for this small room?

Cheers
-j
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Re: full acoustic treatment in a small room

Postby Neokoenig » Sun Nov 18, 2012 5:39 pm

That's almost exactly the size of my drum room. I went for serious isolation + as much bass trapping as possible.

See: http://www.flickr.com/photos/oxfordalto/sets/72157626112927865/
Done by Max Hodges: http://www.maxtech-audio.com/ - he's an awfully knowledgeable chap, well worth getting him for a day to give you a low down.
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Re: full acoustic treatment in a small room

Postby Bob Moose » Sun Nov 18, 2012 7:59 pm

Neokoenig wrote:That's almost exactly the size of my drum room. I went for serious isolation + as much bass trapping as possible.
Thanks for sharing your experience, and congratulations for this nice drum room!
You mean, the size of your room before or after acoustic treatment and sound proofing?
For my own room I will not add any sound proofing because it's not really required (no acoustic instruments nor recordings). Later, if things go well, maybe I can have a larger room where I can (finally!) put some acoustic instruments.

From the pictures your bass traps are simply wall cavities filled with rockwool... but they look very big. Do they absorb mid-high frequencies too, or only bass?

Done by Max Hodges: http://www.maxtech-audio.com/ - he's an awfully knowledgeable chap, well worth getting him for a day to give you a low down.
I would really want to meet Max but I'm not in the UK.
That said, I know a good professional here and will call him tomorrow, just to get an idea about the price

All the best
-j
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Re: full acoustic treatment in a small room

Postby Jack Ruston » Sun Nov 18, 2012 8:14 pm

It's a workable size for a control room and the fact that you don't have to build a room within a room for soundproofing is a great help, because your 2.3m would have made that awkward. I think once you establish a good spot for the speakers, bass trap the vertical and ceiling corners, and damped the first reflection points, it'll probably sound pretty decent. You may need to make sure that nothing in the room resonates too much. Good idea to consult a professional if you can but there's also a lot of info available online.
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Re: full acoustic treatment in a small room

Postby GIK Acoustics » Tue Nov 20, 2012 4:54 am

Hey Bob,

As you've noticed, there are many different ways to go about treating a space. A lot of it depends on your budget, time, and preferences of the room, as well as the current problems the room has.

Yes, broadband absorbers are usually the first preferred method, since they can fix many room issues - from modal standing waves, to flutter echo. However, some people prefer a more "live" room and end up going with tuned absorbers or the like to address particular bass issues while keeping the other frequencies in tact. Lastly, you could also build broadband absorbers, but with some reflectivity as you've suggested so that you don't end up over dampening the highs.

I would be cautious when building tuned or membrane traps as small nuances can affect performance completely. The nice thing about buying pre-manufactured ones that are tested is you know exactly where and how they will work, can be guaranteed results, and usually get free professional advice for how to use such products.

The size of the room is a factor, as well as wall construction, etc. If you want, you can go ahead and fill out one of our room set-up forms to get some recommendations, and you can include pictures, desired results, budget, etc in it here: http://gikacoustics.com/acoustic-advice/
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Re: full acoustic treatment in a small room

Postby Bob Moose » Tue Nov 20, 2012 2:29 pm

Thanks for your answer Jack
Jack Ruston wrote:I think once you establish a good spot for the speakers, bass trap the vertical and ceiling corners, and damped the first reflection points, it'll probably sound pretty decent.
What do you mean by 'pretty decent'? Isn't there a way to make it sound a lot better, for example adding more bass traps? This room could be fully covered by DIY bass traps, if it is useful.
Or is it simply impossible to get a neutral bass response down to about 30Hz in such a small room?

Good idea to consult a professional if you can but there's also a lot of info available online.
I contacted some on the phone. They seem to fall into 2 categories here:
* the ones who try to sell me commercial acoustic foam panels or wedges for making bass traps
* the ones who say it's strictly impossible to make a serious professional studio with a 2.3m ceiling (the other dimensions do not seem to bother them, though)

Quite discouraging actually
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Re: full acoustic treatment in a small room

Postby Bob Moose » Tue Nov 20, 2012 3:38 pm

Thanks for your answer Alexander

GIK Acoustics wrote:As you've noticed, there are many different ways to go about treating a space. A lot of it depends on your budget, time, and preferences of the room, as well as the current problems the room has.
I need a room that sounds the most neutral possible, but it looks difficult because of the limited size. The problems are the usual ones that you find in small rooms: irregular bass response, early reflections, and minor flutter echos / ringing. Only the irregular bass response is difficult to correct. If I DIY everything the budget is not really a problem, and I can accept that it takes some time.

Yes, broadband absorbers are usually the first preferred method, since they can fix many room issues - from modal standing waves, to flutter echo. However, some people prefer a more "live" room and end up going with tuned absorbers or the like to address particular bass issues while keeping the other frequencies in tact. Lastly, you could also build broadband absorbers, but with some reflectivity as you've suggested so that you don't end up over dampening the highs.
Yes, the idea of covering everything with broadband bass traps + some reflectivity was for keeping some liveliness while absorbing as much bass reflections as possible. But even if I cover everything with large bass traps (say 100x100x141cm triangles for the front vertical corners, 40cm deep on the other walls, about 20-30cm on the ceiling), which requires to build a solid structure inside the room, then I'm not sure the bass response will be flat enough.

I would be cautious when building tuned or membrane traps as small nuances can affect performance completely.
Actually I never wanted to make tuned bass traps with a sealed box. The membrane I talked about was just something soft and heavy to put on the rockwool, as you do with FRK.

The nice thing about buying pre-manufactured ones that are tested is you know exactly where and how they will work, can be guaranteed results, and usually get free professional advice for how to use such products.
I must say the GIK panels are attractive, and available in Europe. What bothers me is spending money on a small room: after the treatment, if it only sounds good between 100 and 10000Hz it's going to be deceptive. I mean, I do need a room for professional work, not an average home studio. I have always lost a lot of time working in bad rooms (trial-and-error mastering, if you see what I mean). If it's too small, maybe the first thing I have to do is looking for a larger room.

The size of the room is a factor, as well as wall construction, etc. If you want, you can go ahead and fill out one of our room set-up forms to get some recommendations, and you can include pictures, desired results, budget, etc in it here: http://gikacoustics.com/acoustic-advice/
So is it a free service? Here all the professionals ask for quite a lot of money just for doing a preliminary study.
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Re: full acoustic treatment in a small room

Postby GIK Acoustics » Tue Nov 20, 2012 5:38 pm

Hey Bob, a few points:

We don't build any traps with FRK or foil/kraft paper on the insulation. We do have our FRL trap that is a membrane trap, but it isn't a limp membrane. Perhaps that is what you were referring to?

Our FRL traps have worked in situ (in real world tests) down to 30 Hz. Though your height is quite low, I believe you can easily get good results out of the room, especially with the decent L & W you do have. FWIW, I have a tiny 10ft x 10ft x 8ft studio that is +/-5 dB in the low end, with resonances controlled well, and my room treatment isn't exactly crazy immense. Some good trapping, including corner trapping on the ceiling, would help a lot.

If you would like as well, to figure out the exact problems in your room, you can run tests with programs like REW or similar. If you haven't used REW before, go ahead and check out this video: http://gikacoustics.com/room-eq-wizard-tutorial/

And yes, our room setup assessment is a free service we offer to anyone. If you do run the tests, you can include pictures in the form so you can send pics of the room, drawings of the room layout, acoustic measurements, whatever you have over to us.

This room is slightly bigger than yours, (17ft instead of 15ft length) but the low end is still likely similar. This test shows only the use of our FRL traps to show their impact under 150 Hz. Normally, we would add broadband first and then go with membrane or tuned panels, but a good controlled low end is certainly possible.
This is what we tested:
Image

This is an overlay of frequency response pre & post treatment:
Image

This is a waterfall graph (frequency response over time) showing pre treatment:
Image

Waterfall graph showing post treatment:
Image
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Re: full acoustic treatment in a small room

Postby Bob Moose » Fri Nov 23, 2012 10:38 pm

GIK Acoustics wrote:Hey Bob, a few points:

We don't build any traps with FRK or foil/kraft paper on the insulation. We do have our FRL trap that is a membrane trap, but it isn't a limp membrane. Perhaps that is what you were referring to?

no I was talking about SOS Studio designs that often use an additional membrane
http://www.soundonsound.com/sos/feb06/a ... diosos.htm
http://www.soundonsound.com/sos/mar06/a ... diosos.htm

Our FRL traps have worked in situ (in real world tests) down to 30 Hz. Though your height is quite low, I believe you can easily get good results out of the room, especially with the decent L & W you do have. FWIW, I have a tiny 10ft x 10ft x 8ft studio that is +/-5 dB in the low end, with resonances controlled well, and my room treatment isn't exactly crazy immense. Some good trapping, including corner trapping on the ceiling, would help a lot.

Yes, this is more or less what I would like to do.
When you say +/-5 dB, is there some smoothing here?

If you would like as well, to figure out the exact problems in your room, you can run tests with programs like REW or similar.

Actually, two weeks ago I installed REW and bought an inexpensive measure microphone. I tested it in my living room but still did not have to make measurements in the room I may settle in (it's not in my home).

And yes, our room setup assessment is a free service we offer to anyone. If you do run the tests, you can include pictures in the form so you can send pics of the room, drawings of the room layout, acoustic measurements, whatever you have over to us.

I will do it for sure, but at the moment I am precisely doing all the drawings and collecting some information.

This is an overlay of frequency response pre & post treatment:
Image

Looks good (the waterfalls too), so I guess combining "broadband" bass traps and tuned traps should be the best.
Is there some smoothing on the curve?

Cheers
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Re: full acoustic treatment in a small room

Postby GIK Acoustics » Tue Nov 27, 2012 5:25 am

Hey Bob,

There is no smoothing in the graphs presented above.

Let me know if you have any other questions!
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