The acoustics of large tents

EQ guys are using on their cabs/systems. A good starting place if you don't have your own RTA.
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psjon
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The acoustics of large tents

#1 Post by psjon »

We play quite a few outdoor weddings in the summer and many of them are in a large party tents. This last weekend the tent was 40'x100'. The larger the area, the higher the ceiling generally speaking.

We do our own sound, so I don't have the luxury of wandering around while the music is playing to analyze the sound, but one thing I've noticed is that tents are weird acoustically speaking. My gut tells me that most sound would pass through the tent, but my ears are telling me differently. This weekend I RTA'd the PA which also rings out the feedback frequencies, and I got a lot more ringing than in a more conventional space.

So acoustically speaking what happens to the sound in a tent? Does anybody have any tricks and tips for tents?

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byacey
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Re: The acoustics of large tents

#2 Post by byacey »

Tents are typically a very tight weave material to shed water; air doesn't pass easily through the material either. As a consequence the tent walls are a reasonably good acoustic reflecting surface, or bad for us in this case.
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Rickisan
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Re: The acoustics of large tents

#3 Post by Rickisan »

It would vary wildly depending on number of people inside under the tent and if it has "walls" or is "open air" for the first vertical 8ft or so.

I think it would be advantageous to have something behind the band to help contain/focus/reflect the sound.
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Bill Fitzmaurice
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Re: The acoustics of large tents

#4 Post by Bill Fitzmaurice »

psjon wrote: My gut tells me that most sound would pass through the tent, but my ears are telling me differently.
Your ears are right. It doesn't take a lot of material to reflect sound. There's a prevailing myth, for instance, that a window will act as a bass trap, allowing the sound to pass through it instead of reflecting it back. It's not true. I measured the sound reflections in my house off a 6x6 foot window and the result was exactly the same as off my walls, which have two layers of 1/2 inch sheet rock. A heavier wall will dissipate more energy within it, so less sonic energy will pass through a denser wall, but the amount of energy kept inside doesn't change all that much.

CoronaOperator
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Re: The acoustics of large tents

#5 Post by CoronaOperator »

Bill Fitzmaurice wrote:There's a prevailing myth, for instance, that a window will act as a bass trap, allowing the sound to pass through it instead of reflecting it back. It's not true. I measured the sound reflections in my house off a 6x6 foot window and the result was exactly the same as off my walls, which have two layers of 1/2 inch sheet rock.
I bet if you opened the window the results would be different :wink: .
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Re: The acoustics of large tents

#6 Post by SeisTres »

CoronaOperator wrote:
Bill Fitzmaurice wrote:There's a prevailing myth, for instance, that a window will act as a bass trap, allowing the sound to pass through it instead of reflecting it back. It's not true. I measured the sound reflections in my house off a 6x6 foot window and the result was exactly the same as off my walls, which have two layers of 1/2 inch sheet rock.
I bet if you opened the window the results would be different :wink: .
In that case, they should open up the tent ;) ;)
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Grant Bunter
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Re: The acoustics of large tents

#7 Post by Grant Bunter »

The caveat to byacey's post is:
Yes the walls are tight woven and hence reflective. Unlike a normal room though, the tent walls move! Any breath of wind, a change in wind direction etc etc, will mean that the reflective surface is constantly in a state of change, therefore it reflects differently from one moment to the next. RTA will struggle with that aspect, as the "room" characterstics are not constant.

Sound wise, I find tents to be very decpetive. You know there are reflective surfaces, but all in all, inside them seems flat and lifeless, especially if the tent is set up on lawn.
Concrete or installed floor boards/dance area changes that significantly.

Sure, RTA, but use it as a guide rather than a perfect solution. Tweak by ear :)
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Bill Fitzmaurice
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Re: The acoustics of large tents

#8 Post by Bill Fitzmaurice »

I used to have a regular gig on an outdoor bandstand, one that I built. It had a canvas roof, only about 8 feet high, and the sound on it was quite good, very unlike the usual outdoor gig where you have no boundary reflections. After a few years we expanded the bandstand size and put on a permanent shingled roof. The sound was the same as it had been with the canvas roof.

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dswpro
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Re: The acoustics of large tents

#9 Post by dswpro »

I've worked in large tents from time to time. If you can have the walls rolled up you are in much better shape. If that's not an option when it is raining for example, try to leave some sections rolled up or rolled up a foot or more. You may notice that toward the sides, where the top slopes down to the wall you get much more bass energy. I hate having a mix position near the wall.

I mixed in a new outdoor pavilion last week -- a single pair of T39s and Otop12s on poles.
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