Television Studio Treatment

[SalJustSal]

Hello all,

I work for a local television station in need of acoustical advice. We have a small studio, roughly 20'x30' (although not rectangular). We have a total of 4 LAV (omni-directionals). When one mic is turned on, sound is adequate (although not as dead as to be desired), but when additional mics are turned on, the sound gets increasingly worse with each mic. Our goal is to make the room as dead sounding as possible.

Attached is a studio diagram.

Currently 1" rigid fiber glass sound absorbers are installed on most of the walls facing away from the set. I know that 2" is the ideal number. The set itself is untreated mostly. The green wall (for weather chroma), on the bottom of the diagram is a large 8'x10' flat non-treated wall painted chroma green. I have a feeling a lot of our reflections are coming from this.

Currently our plan of attack is:

-Buying some auralex foam to attach on top of the fiberglass absorbers
1) Is this a good idea? What's the best way to do this? glueing (the covering looks to be a painted canvas)? or pinning?

-Treat the chroma wall. We are thinking of placing some 2" absorption on the wall and creating a floating cloth chroma wall in front of it.
2) Is this a good idea? or would there be a more efficient way of doing this?

3) One concern is treating behind the set. The backdrop is a screen printed canvas, so sound could go through it to be absorbed by some kind of panel behind the set. Is this necessary, since all of the sound from our anchors is directed at the walls away from the studio? or would this be a waste of money.

4) Is sound treatment our only issue? Is there something we can be doing with our mic/board setup to help our problems. I've tried inverting phases, and adding small delays to our mics to help improve any phase shifting issues (since we have 4 omni mics open next to each other) but with little to no results.

 

[bpape]

Skip the foam. 2" fiberglass or acoustical cotton will work MUCH better for the same or less money. To get an equivalent of 2" 703, you'd need 6" of Auralex - seriously.

1" is only killing the upper mids and highs - and doing basically nothing for the vocal range. 2" will be a definite improvement. Male voices can extend down to 2-300Hz. Have you thought about doing anything in the corners to add some additional bottom end control (nothing radical here - we're not trying to tame a sub - just something like some nice 6" in the corners.)

The 2 solid angled panels, whatever they are behind the radius behind the 4 person desk are definitely not helping anything. They're only focusing sound right back at the center.

I think doing a floating chroma 'screen' in front of absorbtion will definitely help.

I'll let someone else speak to the potential mic issues.

Bryan

 

[TexRoadkill]

-Buying some auralex foam to attach on top of the fiberglass absorbers
1) Is this a good idea? What's the best way to do this? glueing (the covering looks to be a painted canvas)? or pinning?

-Treat the chroma wall. We are thinking of placing some 2" absorption on the wall and creating a floating cloth chroma wall in front of it.
2) Is this a good idea? or would there be a more efficient way of doing this?

3) One concern is treating behind the set. The backdrop is a screen printed canvas, so sound could go through it to be absorbed by some kind of panel behind the set. Is this necessary, since all of the sound from our anchors is directed at the walls away from the studio? or would this be a waste of money.

4) Is sound treatment our only issue? Is there something we can be doing with our mic/board setup to help our problems. I've tried inverting phases, and adding small delays to our mics to help improve any phase shifting issues (since we have 4 omni mics open next to each other) but with little to no results.

1. Not a great idea. It looks cool but won't really help the absorption. You would be better off putting the foam on blank areas of the wall.

2. Sounds like a good idea.

3. Probably should be the last line of defense.

4. The only real option would be to go with directional boom mics and that would be overkill. Other then that make sure the talent is talking loud enough that you don't have to turn up the mics as much. Always mute anybody who isn't talking.

With that room shap I'm guessing your getting a longer but more diffused echo. That is good for music but bad with speach. You are going to need to cover as much surface area as possible. The good news is that you dont need bass traps and really thick absorbers to deaden vocal frequencies. 1" 703 should be sufficient.

A big part of the problem is likely the ceiling and floors. You might try hanging some absorption from the ceiling as much as the lighting will permit. You might try putting some packing blankets or carpet on parts of the floor where they won't be in the way.

If you guys have any old Duvatine curtains lying around they make decent sound absorber curtains. A bunch of black Duvatine is also handy for cutting down on room light reflections.

 

[boingoman]

If it's a commercial studio, don't install anything until you talk to your local fire marshall. Likely any DIY stuff like 703 or Auralex isn't going to meet fire codes and would probably need to be torn out the first time an inspector came through. Take the money you would have wasted on that and hire a real consultant.

Don't forget about desks, etc. being potential sources of reflections.

As far as the mics, you might consider talking to engineers at other stations to see what they do. Broadcasters have lots of slick toys most people have never even heard of. My first instinct would be a priority mixer, which can attenuate unused mics enough so that comb filtering is less noticeable, or mute them entirely. That would be after appropriate treatment and mic placement.

 

[bpape]

Hiring a consultant is very good advice.

703 is absolutely perfectly fine in a commercial installation. It's a class A fire rated material. If you cover it with an appropriate material that's also fire rated, you'll be fine.

Bryan

 

[boingoman]

Whether or not a material or installation is OK is up to the local fire marshal. A class A rating is a starting point for approval, not a guarantee of approval.

 

[SalJustSal]

Thanks for the replies.

A few more details. The studio is carpeted to help some. The 1" rigid fiberglass currently has good coverage, covering probably 90% of the walls that are covered, and most of the ceiling (as said before, the chroma wall and the walls behind the set are completely bare). I know the 1" variety does a fair amount of absorption in the mid-to-high frequencies, but parts of human voices (especially males) can go in 250hz spectrum (or lower).

Because of this massive amount of coverage, we're reluctant to take it all down, and would like to try what we can do to add it. The extra cost of the auralex, may still be less than the time/money to tear down the old stuff and put up the new. However, if it won't help to add the 2" of auralex on top of the 1" fiberglass, then I'm sure we're of the impression to do it right and take down most or all of the 1" treatment. So a couple of questions:

5) At 250hz the 1" fiberglass has a rating of between .27-.33 and 2" of Auralex has a rating of .30. If these two were added together, would the equate around .6 at 250 hz?

6) What would be the best way to add the auralex on top of the fiberglass if we were to go this route?

7) Also, would gating help for when multiple mics are open?

And yes, we would need to clear it for building codes before we actually do it.

 

[pandamonk]

Thanks for the replies.

A few more details. The studio is carpeted to help some. The 1" rigid fiberglass currently has good coverage, covering probably 90% of the walls that are covered, and most of the ceiling (as said before, the chroma wall and the walls behind the set are completely bare). I know the 1" variety does a fair amount of absorption in the mid-to-high frequencies, but parts of human voices (especially males) can go in 250hz spectrum (or lower).

Because of this massive amount of coverage, we're reluctant to take it all down, and would like to try what we can do to add it. The extra cost of the auralex, may still be less than the time/money to tear down the old stuff and put up the new. However, if it won't help to add the 2" of auralex on top of the 1" fiberglass, then I'm sure we're of the impression to do it right and take down most or all of the 1" treatment. So a couple of questions:

5) At 250hz the 1" fiberglass has a rating of between .27-.33 and 2" of Auralex has a rating of .30. If these two were added together, would the equate around .6 at 250 hz?

6) What would be the best way to add the auralex on top of the fiberglass if we were to go this route?

7) Also, would gating help for when multiple mics are open?

And yes, we would need to clear it for building codes before we actually do it.

Adding 2" auralex to 1" of rigid fiberglass, will help. 3" fiberglass, or foam, is really affective down to 1.1kHz(due to the thickness), then it'll start to tail off. It might still work well below 1.1kHz, but theoretically(as far as i know anyway), 1.1kHz is the peak absorption. I'd suggest looking up coefficients of 2" rigid fiberglass to find out the what rating it might be at 250Hz.

The best/easiest way to add the auralex to the fiberglass would probably be spray adhesive.

Gating might help, but I have a feeling it wouldn't sound to great. You'd probably hear the gate every tiem it opened and closed.

 

[bpape]

2" OC703 flat on wall - 125Hz through 4kHz

0.17 0.86 1.14 1.07 1.02 0.98

0.86 at 250Hz will do a pretty good job on the vocal range. Space a little of it 1" off the wall and it will do even better.

As for removal, I don't know that you have to pull down the existing. You can in theory (depending on how it's covered), go right over the top with another 1" or 2" layer of 703. Obviously, pulling it down and doing it from scratch will yield the best look and longest lasting installation but in a pinch for the short term, you can do a few areas with the extra layer to get you by.

Bryan

 

[mshilarious]

What is your budget for this? Because my advice would be to hire a qualified local firm that installs acoustic wall treatment. We are cheap bastards here, so we like to bang together DIY panels, but a professional studio should have a pro installation--that usually comes with consultation with a qualified acoustician.

As far as your mic setup, honestly I don't know if treatment would do that much. It could, but the problem you are having with bleed could due to direct sound. Try to increase the distance between anchors (even a few inches might help), or get the lavs closer to their mouths if possible. You could try gating the mics. You could also try to EQ each mic based on the anchor; for example you could set higher low cuts on female anchors.

 

[SalJustSal]

Thanks again everyone,

Hiring an acoustical consultant would be very expensive, due to being in a smaller town, there isn't anyone around here that I know of. The construction company that was involved with one of the other Television stations is the one that did ours, and their installation seems unsatisfactory. So we'd have to call in someone from a larger city. I will have to talk to see what's in our budget for it.

Also we aren't looking for a complex acoustical setup. We're mainly just trying to deaden the room. It would be a different story if we were going to record music in the studio.

I think our problem might be 2 tiered. One is that we have 4 omni mics next to each other, causing some phasing problems, but then we have a not-so-dead sounding room, so as more of these mics are opened, the qualities of the room are amplified. I'll have to experiment with gating and EQing while we figure out acoustical treatment.

Thanks again.

 

[TexRoadkill]

Gating may work if you only use them to duck the signal and not completely mute it. But that's really what the sound man is for. He needs to ride the faders. When several mics are open on a major tv show you can start to hear the room a bit. The sound mixer has to be on his toes.

If you guys already have that much coverage then the only thing to do is cover more or just add to it. You can add another inch or two of 703 to the existing stuff. Adding Foam will be better then nothing but not as good as adding more 703 of the same thickness. As an experiment you might try covering the desk with a blanket to make sure that it isn't the cause of a nasty reflection.