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ADR studio treatment Dynamics Processors (HW)
Old 8th September 2011
  #1
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ADR studio treatment

I know this might belong better in the acoustics forum...

At our post facility I'm not the one making the final calls although I do often get stuff the way I want it. But sometimes money and lack of acoustical understanding from my boss puts me in a tight spot. Thats where I'm at right now.
A new ADR room built, nice and quiet but the squareish shape still make it sound a bit boxy.
Unfortunately we have to get this room running ASAP.
So i need some suggestions on how to best reduce standing waves and reflections in the low mids ( 150-400Hz).
I guess just removing the existing acoustic treatments and putting another layer of isolation behind it might do some good but the easy and fast solutions is what is needed right now.

Room size approx 6x4.5 meters rectangular.

Suggestions welcome.
Old 8th September 2011
  #2
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Kuba_Pietrzak's Avatar
 

How high is it that room? This might matter...

Kuba
Old 8th September 2011
  #3
Hi,

Given the need for something improvised and this is really off the top of my head a few heavy thick upholstered couches and chairs might help break things up.

Hope this helps,

Rob Walker AMPS
Old 8th September 2011
  #4
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Better measurments:
246cm height, 460*410
I didnt measure before, it was just the size as I remembered. Its more square and less rectangular then I thought it was (unfortunately)

All paralell walls and ceiling...
Old 8th September 2011
  #5
Gear Nut
 

I just bought a room kit from gik. It's fantastic. Their stuff is not very expensive, installes quickly so you'll be up and running right away, and your room will sound great. The corner fill bass traps make all the difference. You can add some diffusion later if you need to liven it up a little.
Old 8th September 2011
  #6
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minister's Avatar
I would break the parallel by using some fiberglass panels and angling them off a wall. Or make an A-frame with them. You could on what will be the back wall, take some 2" thick (sorry standard US measure, whatever your Euro equivalent is) standard size (pre-made) panels and angle them from the bottom out, and on top of that place a nice plank of wood so that you have a shelf. Talent can put water, keys, cell phone, etc. Also be sure to stuff insulation between the panels and the wall. You may have to frame this with wood so it is sturdy. You can also do this again above the first panels on the back wall. Now you have broken the parallel with the front.

For the ceiling, hang some panels from chain, but angle them. For the sides, take the one and put some kind of A-frame panel arrangement on it.

Then, get some Pink Noise, a speaker, a test mic and an RTA and shoot the room. You will probably have nasty resonances. If you are so inclined, do some research on DIY (Do It Yourself) Helmholtz boxes.

Bring in an upholstered chair or some such, this will help too.
Old 8th September 2011
  #7
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minister's Avatar
Here is what we did for our one parallel wall (the others are angled).

Those black panels are removable.
Attached Thumbnails
ADR studio treatment-booth_01_sm.jpg   ADR studio treatment-booth_03.jpg  
Old 8th September 2011
  #8
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Thanks for the suggestions.
I have a pretty decent idea if how it should have been done (but wasn't).
I will start with the quick and dirty suggestions.
Weirdly enough when I ran pink in the room it looked pretty decent, some humps and definitely a 70 Hz ish node that almost cancelled in one area. It actually looked better than a lot of studios I have done noise checks as well...
So I suppose to really find the issues I have to use sweeps or ir with EQ wizard. But I have no experience with that so far, and not enough time to get anywhere near proficient until the room needs to be up and running.

Interesting enough when I replay a mix i did in our mix room it sounds quite balanced. But when I record I can hear that there has to be some nasties in the low mids. Real low frequencies are always hard to deal with in a small room, but as it will mostly be used for ADR that shouldn't be a huge initial issue I think.

Putting a regular 2" soft accoustic wall panel at an angle will that become an actual angle at 150-250 Hz or will it bounce on the actual structural wall that is still parallel?
Old 8th September 2011
  #9
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soundboy's Avatar
You will need bass traps. 6" of OC703 in a frame covered with a cloth you can breath through. These will help. In a small room you will also need some diffusion. Look at QRD diffusers.
Old 8th September 2011
  #10
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danijel's Avatar
Here's my cheap 2c:
- spend quality time looking for the best spot for the talent and the microphone in the room as it is. Carefully picking the positions will go further than most bass traps.
- get a multiband compressor on the input channel and tune it to tame the first resonance in the room. Carefully picking the parameters will go further than most bass traps.
- go to the beach with your family while the sun is still over our hemisphere
Old 9th September 2011
  #11
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Thanks Daniel.
Not much sun today I'm afraid and autumn is here. So I really don't feel like going for a swim.
When I moved the mic around I didn't feel it changed significantly so it seems a bit hard to find the golden spot.

It's not a disaster by any means but still...
Old 9th September 2011
  #12
Erik,

Get some heavy drapes and hang them from a rail attached to the ceiling (if possible). Theater curtains work quite well. Create a space about 2.5 x 4 meters, which should be plenty of room for actors to move in. This should take care of most of the modal node problems and will give you a room dead enough to record ADR for outdoor scenes. When you want more room sound, just open the drapes a bit.

I work in several ADR rooms that are set up like this and the sound I get is always top notch. Plus, it is fairly easy to change the sound characteristics of the room. If the space is big enough, it is a good idea to set up two mics, one that is surrounded by the drapes and one that isn't.

Cheers,

Chris
Old 9th September 2011
  #13
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minister's Avatar
Quote:
Originally Posted by ErikG View Post
Putting a regular 2" soft accoustic wall panel at an angle will that become an actual angle at 150-250 Hz or will it bounce on the actual structural wall that is still parallel?
Quote:
Originally Posted by minister View Post
You could on what will be the back wall, take some 2" thick (sorry standard US measure, whatever your Euro equivalent is) standard size (pre-made) panels and angle them from the bottom out, and on top of that place a nice plank of wood so that you have a shelf. Talent can put water, keys, cell phone, etc. Also be sure to stuff insulation between the panels and the wall. You may have to frame this with wood so it is sturdy.
This should take care of your concern. I didn't measure before and after,so I can't say how low it goes, but certain down to 150 Hz, and below. The panels come out about 6" at the top and there is insulation packed in between the wall and the panel. It is a kind of bass trap.
Old 10th September 2011
  #14
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ggegan's Avatar
That's a room ratio if 1:1.6:1.87, which isn't great, but it could be worse. At least it isn't a perfect square or a cube.

You really should post in the acoustics forum for the best advice, but I can pretty much tell you what their advice would be. Angling the walls probably won't help with the lowest frequency modes unless you make them pretty massive with double drywall. It will help reduce flutter echo at higher frequencies if that is a problem. You are going to have to use broadband absorbers to tame the modes.

1. Measure the room with a swept sine, moving the mic to various places and using the waterfall graph to determine where the modes are least problematic. This position will be where you should place your ADR mic. I would guess that you may find this position to be slightly off center, approximately 175cm from the 410cm wall and 150cm from the 465cm wall, but you have to measure to know for sure. BTW, FuzzMeasure is a lot easier to learn than REW.

2. Use a wavelength calculator and a room mode calculator to determine which dimensions are creating the remaining problem modes.

3. Apply broadband 703 absorption panels to the walls generating the problem modes. They should be at least 10cm thick, preferrably 15cm, with at least 5cm airspace between the back of the trap and the wall. Put superchunk wedges floor to ceiling in all four corners, 80cm faces if possible, otherwise 60cm.

4. If you can stand to lose some height, even if only 15cm, install a drop ceiling with acoustic tiles and stuff pink fluffy insulation in the space above it. If losing that much height is unacceptable, consider a soffit running around the perimeter of the room that is faced with 5cm 703 and stuffed with pick fluffy insulation inside.

5. Measure again and tweak the placement of treatment.

This will make the room pretty dead, but will help with the modes. You might be able to put a couple of 1D Schroeder diffusers on one of the 410 cm walls if you make sure that the mic can be placed 275cm or more away from the diffusers. They wouldn't help with the low mids, they usually are designed for about 800Hz and above, but they might help bring a little life back to the room.
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