Dampening a Super Reflective Stage (Daggumit!)

[Micklure]

So I just took over a job for which I interned for several years (take that, unemployment). I'm the TD for the primary performing arts hall for a small university. Instead of a typical theater with curtains and the like, it's a proper concert hall (see pic attached.) No curtains on stage, lots of beautiful reverb, and high ceilings. It's breath-taking when we have orchestras. But when we have rock bands, big bands, and jazz combos, it's an unholy clamor. The towers you see on stage can be arranged to reflect sound as desired. Again, very useful with orchestral groups, but not so helpful with drums and monitors. The clouds you see are roughly 30 feet from the stage floor and the ceiling another 30 or so. Despite the size of the space, we only seat around 350.

Fortunately, student ensembles make up the bulk of our performances. However, we have enough bands come in that it would be worth addressing the issue. The problem, of course, is that we don't want to permanently dampen the hall. Ideally, I could have a setup that would ease things as needed and be taken down afterward. Thankfully, we have carpet flooring in the aisles and heavy curtains on the walls surround the seating, which helps a bunch. So the issue is limited, largely, to the stage. Can't do much about the high ceilings, but I have some thoughts for the stage. I'd like to share my plan with you and get some feedback.

For the groups that need dampening:
-Cover the stage with large, black, commercial-grade, carpet mats OR interlocking trade-show carpet tiles.
-Push the sound towers back as far as possible.
-Backdrop the group with black, 8 foot pipe/drape
-Cover the face of each tower with additional pipe/drape (which would make some cool uplighting opportunities too!)

Thoughts?

Picture:
http://s16.postimg.org/z2kfpc12d/IMG_1063.jpg

 

[sk8rsdad]

It is hard to tell from a picture exactly what is producing the reflections and resonance but treating the major contributors would be the best bang for the buck.

My first thought is getting some FR fabric covered rigid acoustic batts made as inserts for the reflective panels. A floor treatment would help with reflections and resonance of the floor, if that's the culprit. If you want to soak up reflection then suspended baffles may be the most effective, but not necessarily the easiest to rig and remove.

 

[rwhealey]

To clear up some technical terminology, you have an issue with an excessive reverberation time for the modern music events. This isn't uncommon - your hall was probably designed for unamplified music. You do have some variable acoustics in the audience area, but it sounds like it's not enough. What you are calling "dampening" is more precisely called "sound absorption". Dampening is a material that is added to a vibrating surface to prevent or mitigate the surface from creating sound, while absorption is used to reduce airborne sound reflections.

I recommend that you hire an acoustics expert - simply adding more absorption into the room may not solve the problem, as not all absorption works at every frequency. There is a lot of research that indicates that low frequency reverberation ( < 500 Hz) is the most bothersome frequency range for rock and pop music. It's also a lot more difficult to add absorption in those frequency ranges, so getting an expert opinion would be the best idea. They will let you know exactly how much absorption you need to add, hopefully saving you money. Whatever you do you don't want to make something permanent that effects your concerts

I can, however, answer a few of your questions:

-Cover the stage with large, black, commercial-grade, carpet mats OR interlocking trade-show carpet tiles.

This won't help much - commercial carpet is much less absorptive than many people believe. You will only notice some high frequency effects.

-Push the sound towers back as far as possible.

This won't change the reverberation time.

-Backdrop the group with black, 8 foot pipe/drape

Probably your best option. You will want to use a heavy material, though - not the thin stuff that a lot of production companies use when you rent pipe and drape.

-Cover the face of each tower with additional pipe/drape (which would make some cool uplighting opportunities too!)

This would also be effective, assuming that you also use heavy drape.

 

[venuetech]

What does the back of the towers look like?
Could you install something on the back so it would be a simple. Matter of turning them around for witch ever type of performance.
I would try various configurations of the towers. So for a power act I might try a series of two towers formed in a V with 10' gap from the back wall. It looks like you have ten towers so it would be V V V V V. Or am I looking at Just 6 movable towers?
The idea is to breakup the sound wave. I think you would want large gaps between them.
If you do push the towers against the back wall stagger them so every other one is 5-8' down stage

 

[Ford]

I believe that Gerrits makes a velour specifically designed for sound absorption. The Kiplinger theatre at Cornell has tracks installed around the entire outside edge of the house, for acoustical curtain... However, the curtains themselves were never purchased (as far as I know) because they are expensive, would need to be stored when not in use, would need flame proofing certification redone every few years, and things like tools and there were the inevitable cost overruns at the end of the project that ate into every "non-essential" capital request.

If you do go with a pipe-and-drape type solution, make sure that you use a heavy velour, and that you get the flame certification.

Good luck,
-Ford

 

[BillConnerFASTC]

Good ideas above. You need absorption with depth for the lower frequencies. Venuetech's idea was what I thought of - thick absorption on rear of towers. It will of course affect the natural acoustic events a little but not much. To make a big difference will take some rigging I think - and hoisting some heavy fuzz high - and storing it outside the room.

I wonder if they knew when planning that there would be the types of events you mention, or if the natural acoustic people just spoke louder or gave more money.

 

[gafftaper]

First off congratulations on the job and welcome to The Booth!

As has been said you need to hire a consultant to do this right. You could easily spend thousands, if not tens of thousands, doing this yourself and get mediocre or possibly no results. Sadly we had a great consultant who hung out here on CB regularly and lived in Georgia, but we lost him to Leukemia last winter. But, if you need help finding a consultant start a private conversation with @BillConnerASTC . If his company can't do the work, he can definitely help you find someone good who can.

Would "the powers that be", be open to having truss permanently installed over the house? My thought is you could permanently install truss on motorized hoists. In normal acoustic type events you could store the truss all the way up near the ceiling. Then for a louder concert, lower it down, attach the baffles, and position the truss in a lower position. It would be expensive but would give you maximum flexibility with a minimum amount of permanent change and, with the help of a consultant telling you where to position the baffles, it could be very effective.

 

[Fountain Of Euph]

I have almost the same situation in my space. The first thing i that i do is to use the space to my advantige. I limit the number of monitors and mic sparingly so as to get the cleanest mix.
Part of my issue is the lack of investment (both financially and interest) in my space by higher ups. If your school is willing to invest in making the space good, then get a consultant as soon as possable

 

[jonliles]

Is this Oglethorpe or one of the older GSU spaces? Spaces is familiar looking, just trying to figure out where.

 

[derekleffew]

http://blog.rosebrand.com/post/2015...ail&utm_term=0_78e0a95399-a5f328437a-26447301

 

[rwhealey]

http://blog.rosebrand.com/post/2015...ail&utm_term=0_78e0a95399-a5f328437a-26447301

While there isn't anything wrong in this article it is pretty highly biased towards using fabric and drapery for sound absorption - which makes sense since it's Rose Brand. Fabric and drapery can work well but also can be fairly expensive and may not have the low frequency absorption that is required. There are other options out there that are cheap, like perforated PVC banners (http://mbiproducts.com/products/cloud-lite/) that may be quite a bit cheaper than drapery.

 

[AlexDonkle]

I would try to dig up the original permit drawings for the construction of this room, and find out who the original acoustical consultant was. If you email them, you may find out more specifics on the room's construction that could be helpful (they may have planned for future acoustical banners during construction). If they're not available, I would still recommend bringing one in to measure the room and provide some recommendations for how much treatment would be needed for a noticeable difference. Naturally I'm a biased source on consultants though...

Also, is the complaint from bands related to loudness (likely direct reflections from room surfaces), general music clarity / sounds mushing together (likely overall reverberation time of the room), or both?