Acoustic Experts - I need you!

C

Christian Boche

Junior
May 18, 2012
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I need your help concerning acoustic improvement for a small Live Music Venue (250 pax).

Some friends of mine run this venue as a public charity and I'm doing the live sound (FoH) and installed the small pa system. Of course everything runs on a tight budget, so except for some molton curtains we didn't installed any other absorbers yet. I tried my best, to install the pa system in a way, that it doesn't cover much of the walls. The tops (60x40°) are flown, angled and the four 18" subs were clustered, delayed and EQed with help of the Ray End and Systune.
So the sound is at least decent when doing DJ events.

Main problem is:
The overall sound is too reverbant for loud bands, and there are hearable flutter echos from the ceiling and the rear wall.

So my idea is to put some absorbers on the ceiling above the stage and to tame some of the direct reflexions of the back wall (opposite the stage). I made some measurements with REQ and it seems, that my main problem is the long RT60 between 300 and 3000 Hz. I know, the lows aren't perfect, but we don't have the budget to build some massiv bass absorbers, so we try to love it the way it is. Actually, it sounds better than it looks;-)

But maybe some of you have some ideas, what economic absorber will cover the 300-3000Hz area, are easy to build and where to put them???

In addition, it would be nice, if the new absorbers won't harm the heights too much. Also, this is a public place, so the absorbers should be incombustibleor at least low-flammable.

Here are some pictures/facts, that might help:

The audience area is 11 meters long and barley 7 meters wide. Stage is about 6 x 5 meters. The venue has a pointed roof (highest point is about 5,5 meter).

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Christian
 
Re: Acoustic Experts - I need you!

Christian....

Don't forget diffusion. Absorption can start to make a room feel "dead". Think about breaking up the flat surfaces with shapes and textures. Absorbing the high frequencies can throw the space out of balance as it is much harder to build LF absorbers/traps.......and you lose space for the depth necessary for LF treatments.

A balance of absorption and diffusion is what I'd look for.
 
Re: Acoustic Experts - I need you!

Hey Chris,

I think the RT60 with roundabout 1.. second is not much to much and for low frequencies it could be a bit more.
Do you have an Impulse response, maybe we can detect the distance/ways of the flutter echos and Break them with diffusors on the backwall/ceiling.
Maybe combined with a absoprtion, but perhaps with the audience the absorption could be quick too much.
 
Re: Acoustic Experts - I need you!

Thank you guys,
valid points here!

To make my point clearer. All measurements were done with the actual pa system in that room. This explains the bass overhang, the dip between 2-4kHz and some of the high frequenzy roll of. It comes mostly due to the speaker controller setting. The bass response is not that bad in the room, we can deal with that. It is the "roomy&boxy" sound in the mids, that is annoying. And the reflections from the ceiling above the stage is giving me a headache.

We are willing to spend some money on the acoustics (and labor as well of course), but where to start?

@Tobi: Yes, I did eight measurements on different positions and I have all the impulses, but I'm to stupid to "fenster" them correctly. I dont know the english word for that...I mean, to set up a filter on the IR, so that you can distinguish between the impulse and the first reflections. I can set up a pa system quite good, but I'm a real noob concerning acoustic measurements:-(
BTW Tobi, do I remember right, aren't you a student in this field?

Thanks
Christian
 
Re: Acoustic Experts - I need you!

Fenster:Window

Here's a picture of the interior of the McGuire auditorium at the Walker Art Center in Minneapolis. Note the "sculpted" nature of the facings on the balconies, etc. The material is actually metal. Besides having artistic contours to diffuse the sounds, the material is also perforated to regulate the HF content in the room. As an acoustic space it's a bit dead for my taste, but the house hangs are Meyer, I think, and when cranked up the room is sweet and even.
 

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Re: Acoustic Experts - I need you!

Before you get too far you might also want to consider that (hopefully) the room won't be empty in actual use. Some people in the space may provide a good amount of absorption and diffusion while ambient noise may also help mask lower level acoustical issues. Unless you model the room with and without and audience then guesstimating the effect of an audience is still somewhat an art.

For a black finish like that something like Commercial Acoustic Systems: SelectSound® Black Acoustic Board can be very effective, the 2" thickness has pretty good absorption values throughout the frequency range you noted and it typically meets flame spread and smoke developed requirements (although that should be verified for the specific project requirements). There is probably something similar available there if that specific product is not available.
 
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