Acoustic treatment of large room for live music performance

[Sam Amato]

OVERVIEW:
I am planning to treat the acoustics in this room to improve the sound when live bands play there. This is not going to be a "music venue" but there will be live music from time to time. Sound isolation is not a concern. Currently the room is all hard surfaces everywhere and the reflections are quite a problem.

My band played there recently for a private party. During the first set we could not adjust our levels enough to make it sound good, for us or the guests. After that we had the drummer use "rod" sticks and play much quieter and we were able to make it enjoyable for the guests but it was still a mess as far as I was concerned.

The owner is aware of the issue and willing to invest some money to improve the acoustics. I told her I would come up with a plan and present it to her. I don't plan to charge much for my services. It's more a learning experience for me and hopefully it will lead to more bookings there for my band.

There are limitations to what can be done. She is not willing to change the "interior design" of the room much, if at all. All the artwork must stay and what I put up must not distract too much from it.

I'm thinking of using simple broadband absorption panels like these: http://www.johnlsayers.com/phpBB2/viewt ... =3&t=10297 and doubling up the insulation for corners. Some clouds are possible but there are sprinklers to be concerned with. My basic idea is to put up as many wall panels as possible and maybe a cloud over the area where the bands play. I told the owner the band area might need more treatment than the rest of the room. She asked if maybe moveable panels would be possible for that area; so that is another consideration.

Here is my effort to provide all the information you guys need to help:

01) I have been reviewing the reference area of this forum for several years now, though my understanding of it all is basic and I have only limited practical experience.

02) The forum search feature has been very helpful. I believe I can make and mount the absorption panels I need for this project with no problem based on what I've learned here.

03) The place in question is a winery, where they make and serve wine. It is near downtown Orlando, FL, USA.

04) I am in the research and planning stages. I'd like to submit a proposal and start doing the work ASAP.

05) HOW LOUD? I don't have a way of measuring this at the moment. They do not have live music all the time, only for certain events. Since isolation is not a concern I'm hoping this is not a problem. I can go in and analyze the response of the room with the proper microphone and software (probably using P.A. speakers for playback) if necessary, but have not yet done so. I'm wondering if this is needed, as there are limits to what I can do cosmetically and financially anyway. I believe we all pretty much know what a room like this sounds like with loud music playing in it. I think I just need to "deaden" the room as much as possible but I don't want to waste time and money on things that will not provide the desired results.

06) The floor, according to the owner, is concrete slab->some kind of "acoustical pad" (I'm guessing some kind of rubber material?)->cork tiles. Walls are concrete block. There are 2 large glass doors, 4 smaller steel doors. I am unsure of the ceiling construction.

07) No plans or need to float the floor. Isolation is not a goal here, just need to make it sound better inside the room for both the customers and musicians.

08) The room is basically a 49' 9" x 40' 1 1/2" rectangle with a ceiling height of 18' 8".

09) I have attached photos of the space and a couple sketchup drawings to show a little more detail.

10) I believe the size of the photos is right for this forum but if not I will try to fix them.

11) Photos are linked to this site, not externally linked.

12) No long links here.

13) My questions are listed below.

14) The owner is okay with spending $1,000 on this project. If it needs to be more I will have to run it by her and see what she says. I can get enough Roxul AFB 2'x4'x2" to make 42 broadband panels for around $450 shipped so I'm thinking around $1,000 might be possible.

15) I will patiently await your responses though I'm hoping that I've provided enough information to make it easy for you guys to help in a timely fashion.

Questions:
1) Would just placing 2'x4'x2" broadband panels in as much of the open wall space as possible and a 2'x8'x4" corner panel in the band area be enough to control the reflections of this room so a typical live band (drum kit, electric bass, keyboards, guitar, vocals) would sound "good"? If not, what other plans should I consider?

2) Should I consider the idea of moveable panels for the the "band corner"?

3) Is it possible to get the desired results without using any clouds?

4) Do I need corner panels (bass traps) in all the corners, or can it just be in the "band corner"?

Thank you for your time. I look forward to any input you can provide.

[Sam Amato]

I may have answered some of my own questions, which is always a good thing. I just don't know if my answers are correct.

Using this Reverb Calculator http://johnlsayers.com/Pages/Reverb_Calc.htm, what I'm seeing is not good. I attached a photo of what I entered. The results (not shown in photo) were:

125Hz - 1.89 sec
250Hz - 1.83 sec
500Hz - 0.82 sec
1000Hz - 0.82 sec
2000Hz - 1.04 sec
4000Hz - 1.39 sec

My understanding is that I should be shooting for somewhere around .5 seconds across the board. Since I've already added (49) broadband absorption panels (virtually, not actually), which is probably more than the owner will allow, I guess it is a lost cause.

[Soundman2020]

Hey Sam. Sorry about the delay in responding: There are lots of active threads right now!

Anyway, I don't think it is a lost cause!

That's a nice looking place there, and I can understand some of the restrictions that the owner is imposing, but all is not lost: There seems to be lots of wall area up high, above the area where the artwork is hung, and there are things you cold do up there that would make a useful difference. And you could do it without changing the overall "look" of the place. In fact, some of the things you could do might even be considered as enhancing the look, as they can be done in the same "utilitarian" style.

Currently the room is all hard surfaces everywhere and the reflections are quite a problem.

Yep, I can imagine! That looks like a concrete cave, with large, flat parallel surfaces on all six sides.

I'm thinking of using simple broadband absorption panels like these: http://www.johnlsayers.com/phpBB2/viewt ... =3&t=10297 and doubling up the insulation for corners. Some clouds are possible but there are sprinklers to be concerned with. My basic idea is to put up as many wall panels as possible and maybe a cloud over the area where the bands play. I told the owner the band area might need more treatment than the rest of the room. She asked if maybe moveable panels would be possible for that area; so that is another consideration.

You could do that, yes, but absorption alone is not going to tame that space enough. You are also going to need to add some diffusion, to break up the large flat wall surfaces.

HOW LOUD? ... They do not have live music all the time, only for certain events. Since isolation is not a concern I'm hoping this is not a problem.

It could be a problem. I run live sound frequently for events in all kinds of places, some of which are acoustic nightmares. The best way of dealing with highly reverberant places, such as what you are facing, is to keep things quiet. You already figured that out by "turning down" your drummer, but you you can do things with the sound system itself to improve the overall experience even more. What I normally do in spaces like that is to NOT do what most bands do: A couple of big speakers on each side of the stage, turned up loud enough that people on the other side of the room can hear them. That's a mistake. It means that the speakers are so loud that they are triggering all of the room resonances at once, and also deafening the people up close. The louder you make it, the worse the problem becomes.

Instead, what I do is to use the "distributed" approach: set up several sets of speakers around the room, some close, some further away, with the correct time delays on the far speakers(!), and then keep the level at each speaker low enough so that it only covers a short range, just up to the next speaker. Also, aim the speakers diagonally away from the walls, not parallel to them, and not perpendicular, either. This means that everyone can hear the band clearly, since everyone is within the critical distance (the distance at which the direct sound from the speakers becomes overwhelmed by the reverberant field of the room itself). And the overall level is low enough that you can avoid triggering some of those room resonances, too. You need more speakers and careful setup of the time delays, but this method works very well. If your band has a good sound engineer, then he can do this.

OK, but that still takes care of only part of the problem: Getting the levels down with distributed speakers only helps to a certain extent, and you still need treatment for the rest.

I can go in and analyze the response of the room with the proper microphone and software (probably using P.A. speakers for playback) if necessary, but have not yet done so. I'm wondering if this is needed,

It would be good to help understand the problems in the room. You can download the REW software for free, and use that, then post the resulting data file here, for analysis. Use just one speaker, set up roughly in the center of the stage, and one omnidirectional mic, set up about two thirds of the distance from the stage to the back wall. It is easy to do, and just takes a few minutes.

I believe we all pretty much know what a room like this sounds like with loud music playing in it

Oh yeah! I know what you are suffering! Been there, done that. Many times. But every room is different. They all sound bad, but there are different types of "bad", and that's what REW will show up: what type of "bad" you are dealing with.

I think I just need to "deaden" the room as much as possible but I don't want to waste time and money on things that will not provide the desired results.

With a room that size, deadening it enough would be hard to do! Absorption is only one part of acoustic treatment. Diffusion is another. Absorption works by removing some of the energy from the room, but removing enough is not easy, and the result can even sound "bad" in another way. Diffusion works by breaking up and scattering the sound energy, so it is not reflecting at the same angles all the time. The problem you have now is "specular reflection" from the walls, where the sound is just bouncing off, and following clearly defined paths around the room. If you can break up those reflections and paths, then you get a much more diffuse sound field that does not echo" and "reverberate" like it is doing right now. It sounds more natural, less "hollow", less "muddy".

One very easy way of creating diffusion in a large space like that is with something called "poly-cylindrical diffusers. That's just a fancy way of saying "large round things". There's a simple, cheap way of doing this, too: Sonotubes. Those are large round cardboard tubes that they use to make concrete pillars for buildings. You can buy them at hardware stores and building supply stores. They come in various sizes and lengths, and those shapes and sizes just happen to be useful for acoustics! You could buy a bunch of those, maybe several each of 16", 20" and 24", 8 or 10 feet long (or even longer), cut them in half lengthways so you end up with two long half-cylinders, and set those up against the walls of the rooms, standing up vertically, spaced a few feet apart. Figure out a way to keep them in place so they don't fall over. Paint them white and tan, the same color as the walls right now, in the same pattern, so they are very unobtrusive. They can even be interspersed bet ween the artwork, made to look like part of the walls.

A few dozen of those around all of the walls, plus several of those absorber panels you were talking about, will make a noticeable difference to the acoustics in that room. It won't make it into Boston Symphony hall, but it will probably make it usable. If the experiment works, then you can convince the owner to buy even more of those tubes, longer ones, and attach them to the walls way up higher, on those large flat surfaces where there is nothing right now, where it is too high to have artwork. Up near the ceiling, in the black area, put several of those horizontally too, to provide diffusion in other axes. And if you can, then also put some on the ceiling.

The only issue here might be fire risk, but there are probably treatments that can be applied to the cardboard to deal with that. Not sure. You'd have to check on that.

I can get enough Roxul AFB 2'x4'x2" to make 42 broadband panels

You will need much larger panels than that, and thicker too. 2" is no use for what you are trying to do. Get the 4" panels, 4' x 8', and space them away from the walls at different distances: some at 4", some at 8", some even more, if you can.

1) Would just placing 2'x4'x2" broadband panels in as much of the open wall space as possible and a 2'x8'x4" corner panel in the band area be enough to control the reflections of this room so a typical live band (drum kit, electric bass, keyboards, guitar, vocals) would sound "good"?

By itself, not. Probably not. For the reasons I outline above. Trying to treat that place with just absorption is going to be real expensive, and not very effective. You need a combination of absorption and diffusion. Based on the dimensions you gave, you would need a total of 3,331 square feet of absorption to get that room under control, down the reverb times you are talking about. But those are also unrealistic (I'll get to that later). 42 panels of 2' x 4' would not even amount to 10% of that. You can't treat large spaces with absorption alone.

2) Should I consider the idea of moveable panels for the the "band corner"?

Yes. Make some "gobos", based on the same basic idea: wooden frames with panels of 4" OC-703, on wheels. Put plywood across the back, for both structural and acoustic reasons.

3) Is it possible to get the desired results without using any clouds?

Probably, but they would sure help!

4) Do I need corner panels (bass traps) in all the corners, or can it just be in the "band corner"?

In a room that size bass traps are not that important. It has modal support down to 11 Hz, and good, even distribution across the entire low end. It is much more important to break up the bass energy traveling along the walls and bouncing off it, than to try to trap it.

Using this Reverb Calculator ... what I'm seeing is not good.

It's not too bad, actually, but could be improved.

I attached a photo of what I entered.

Make those 4" thick, instead of 2", and make them 4' x 8'. That should show a bit of difference.

My understanding is that I should be shooting for somewhere around .5 seconds across the board.

For a control room, maybe, but not for a large space like that. 1 to 1.5 seconds or so would be about right, provided that it is sufficiently diffuse!

I guess it is a lost cause.

I don't think so!


- Stuart -

[Sam Amato]

Thanks Stuart, that is good news.

I didn't even know I should be considering diffusion for this room!

My next step is to put together a layout plan for the absorption panels and diffusers in Sketchup. That's gonna be tough for me but I'll try to follow your advice. I'll post it here before I present it to the owner.

[Sam Amato]

Question about measurement mics, SPL meter, and software:

I was planning on buying a Behringer ECM8000 and installing REW software. Reading the calibration instructions for REW, I realized I will also need an SPL meter (seems logical). I'm guessing my "SPL Meter" iPhone app by Studio Six Digital is not accurate enough for this. I did test it against a pro quality SPL meter when I bought the app and it was very close once calibrated but still probably not good enough these purposes, I assume.

I'm trying to avoid buying a mic and and SPL meter right now. Would I be okay if I just bought a Radio Shack SPL meter with a line out and used that as my measurement mic also?

Or another way of phrasing my question: If I can only buy the mic or the SPL meter, which should it be? Can I get by for now with just one or it essential to have both?

EDIT - I'd also like to know if I should consider the MiniDSP UMIK-1 USB mic instead of the Behringer ECM8000.

[Soundman2020]

I was planning on buying a Behringer ECM8000

It works fine, but I have found that it is very sensitive to mains hum, and picks it up very easily.

Would I be okay if I just bought a Radio Shack SPL meter with a line out and used that as my measurement mic also?

Yes, that would work well. In fact, a sound level meter is an amazingly useful tool for any involved in audio, so I would get that anyway. I could not do my live sound events without my meters!

Reading the calibration instructions for REW, I realized I will also need an SPL meter (seems logical).

You only need to calibrate if you want to have accurate absolute dB readings. If you don0t calibrate then the relationships between readings will still be valid, but the absolute numbers will not be correct.

I'm guessing my "SPL Meter" iPhone app by Studio Six Digital is not accurate enough for this.

It might be good enough to get you in the ball-park, so to speak. Once again, it won't be as accurate as a calibrated SPL meter, but all you really want here is to see the relationship between the various frequencies, and how they change over time.

But if I had to choose, I would go with the Radio Shack meter, or any of the decent quality digital meters that you can find on e-bay and Amazon for around US$ 75 or so (not the cheap Chinese junk, for US$ 25!!! forget those....)

If I can only buy the mic or the SPL meter, which should it be? Can I get by for now with just one or it essential to have both?

I would get just the SPL meter with a good quality "mic-out" connection.

- Stuart -