Acoustical Treatment

[Esoteric]

Okay, so I have a client that wont bring in an AE, but they are concerned.

Here is the situation.

They have a LOUD drummer. No volume control. They can not use a full drum shield only a front and side.

Right now they have a lot of very thick black fabric that hangs behind it that absorbs some of the bass and attack from the drums. It takes a bit of the edge off, and eats some volume and kills some echo.

Now for design reasons they are removing the fabric. They will be projecting directly on their back wall. The back wall consists of drywall with on edge metal studs and traditional pink insulation.

What could they do to still have a wall type surface to project on, but still get the sound absorption of the black fabric?

Mike

[cmchamp]

what's the rest of the room like?

[Esoteric]

The SL wall is drywall with studs and insulation.
The SR wall is drywall with studs and insulation and has open vents to the AC air handlers.
The back wall is Drywall with no insulation and double doors basically directly in front of the drums.
There are also metal double doors on the back wall directly behind the drums.
Sloped roof with insulation (all insulation is normal pink fiberglass insulation) and metal perlins.
The floor is carpet over concrete and the stage is raised 36" hallow with metal studs and MDF.
The room is wider than it is long. Holds about 400 according to code (they have put 650 in there before).
The room is also oddly shaped. There are offices SL and SR (behind the projections), there is a cry room rear house right with one way glass, and an electrical room house left. None of the rooms are the same size or shape.

Mike

[tdangelo]

Do they want it to look and feel like sheetrock, or just look like sheetrock?

[[Director] Joseph B]

Perhaps they should just get the drummer under control. We have drummers who were given a choice, play softer or use brushes only.

They all learned to play softer.

[[Director] drew ryan]

How about hanging an acoustically transparent, yet visually reflective fabric in front of the thick curtain that is already there and beneficial?

[Esoteric]

This drummer will never be under control because he does not think he is out of control. And no one want to say anything to him because he is the sound guy. I tried when I was the service producer for a year. So that is a no go. He think it sounds great and no one is going to tell him otherwise. So that is a no go.

As far as hanging fabric in front of the black drapes, we are going to test that, but it is not really the look I was going for.

It doesn't have to feel like anything in particular. As far as what it looks like, just like a wall I suppose. Brick, drywall, concrete, I don't care. It doesn't even have to be particularly flat, smooth, or even. Just a wall.

Thanks
Mike

[cmchamp]

Black drapes, no matter how tightly packed, won't do much for frequencies below 500Hz or so, so the majority of the LF absorption, if any, comes from the wall itself.
I've got some frequency specific solutions that would work, but the drapes would have to be taken off, the room tested, specifically that wall, for what's being reflected from the drummer.
Then, a specific diffusion/absorption product could be designed and placed.
Elsewise, the other option for broadband diffusion/absorption would be possibly sonotubes and/or PVC.

[Brad Weber]

Mike,

You mentioned that they would be projecting directly on the back wall, thus at least that part of the wall would have to be as flat and smooth as possible. Most acoustical material are rough, perforated, open weave, etc. I know of a couple of finishes that can mimic the appearance of sheetrock once you get a few feet away, but those are intended to be installed as ceilings or higher up on walls where people cannot directly interact with them, it is an applied finish that would apparently tend to deteriorate quickly with people touching it, running into it, scraping it, etc.

Since it seems like a projected image would have to be some distance above the drummer anyways, would it be possible to still have draperies or some other acoustical treatments up to a height and then a flat projection surface above that?

You mentioned that this is for a Client, so as a provider to them might you be the one who could broach the issue with the drummer? I've had a number of clients for whom my being able to say things to people without it being a personal issue and without worrying about the internal politics or relationships have been of great benefit. Maybe approach it as that while trying to learn as much as you could about their concerns and goals it became apparent that the drum volume was an issue and since the physical options are limited, any reduction in the playing volume would be very beneficial.

[Brad Weber]

Originally Posted by cmchamp

Elsewise, the other option for broadband diffusion/absorption would be possibly sonotubes and/or PVC.

Cory, have you been able to find anything on either of those supporting that they meet the required flame spread and smoke produced ratings for use in public assembly spaces? I've searched for years for anything definitive supporting that Sonotubes have the appropriate ratings for such use without any luck.

The closest I've been able to find to a definitive answer was a comment by Mr. DeBuglio, probably the biggest proponent of Sonotubes for diffusion, that "The other element is to cover them in carpet. Just remember that these are a fire hazard so you may want to cover them with a fire rated carpet.", however my understanding is that covering Sonotubes with a rated carpet does not make the assembly rated, that would require it being tested and rated as an assembly and I cannot find any evidence that has been done.

This is an area where until I can find something formal from the manufacturer or UL stating definitively that they can be used in such applications, I will err on the side of caution and assume them to not be acceptable.

[Esoteric]

Brad, it is environmental projection, so the surface does not have to be particularly smooth or even. It is an effect, you don't have to be able to read anything on it. So I am not worried about finishes.

The projection is directly behind the drummer. So that is an issue.

Could I do PVC behind drywall?

I have tried telling them/the drummer about it. I did during the original install, my time as producer, multiple times. He refuses to listen to anyone, he thinks it sounds great. I even got confronted as Producer once when I was mixing because I pulled the kit down about 33% for my mix.

Mike

[cmchamp]

PVC behind drywall, no. The purpose of the curved surfaces would be to provide diffusion.
Possibly, then, the other solution would be to frame panel absorbers with a scrim over them?