Sound For Really Long Halls |
May 11th, 2011 |
| contra, sound |
When the swarthmore
folkdance club holds contra dances in upper tarble they like to
make a single really long line. The hall is quite large, and it's
nice to dance with everyone. I remember liking doing this when I
was a student there. One thing I didn't think very much about at
the time was how difficult it is to deal with sound when you have a
large live hall with a really long line. If you put your speaker at
the front, it's too loud in front and to quiet in back. If you put
it in the middle it doesn't disperse properly. If you put a second
one at the bottom of the hall facing back up dancers lose their
location cue of the music coming from the top of the hall and the
band. If you put a second speaker halfway down you need a delay and
the bass being non-directional will sound bad (a little muddy and
unclear) up the hall from the second speaker. All of these that use
a second, remote, speaker suffer from the annoyance of running
longer cables (and having an additional speaker). Getting the main
speaker higher would help a lot help, but the school wouldn't let
you hang anything and the speaker system the club usually uses puts
the speakers a little below head height.
When we played there in march (which was really fun!) we switched to using one of our monitors (a QSC K10) as the only speaker near the beginning of the night, and that worked well. I think much of it was just getting the speaker to be a few feet above head height. There was still too much of a volume difference between the top and the bottom of the hall, but it was better.
A real solution would be to convince people to dance in two shorter lines. But the dancers don't see it as being worth it.
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Couldn't you fix the muddy bass problem by filtering out low frequencies from the middle speakers and having louder bass at the top of the hall?
@David: probably. Alternately, only putting the caller in these speakers (because clarity of instruction is more of an issue than too quiet music). But the inconveniences of a second set of speakers, the longer cables, and a delay are great enough that I'm not excited about this solution.
David's right about not putting any bass in the fill speakers. However, Jeff's certainly right about it being a pain to deal with fill speakers. In a hall where you can raise the speakers and have a central cluster, that works, but obviously professional rigging is not an option in this situation. Another solution that's impractical but addresses the problem is a set of narrow dispersion line arrays at the top of the hall. Note that line arrays only do so much, which is why the Dance Flurry's Room D has both line array main speakers AND still has fill speakers -- but fewer fill speakers than if they had conventional main speakers.
Penultimately, you can make delayed fill speakers more tolerable by using remote speakers of some sort -- power line transmission or radio.
Finally, when you were a student there, you didn't notice the faults in the sound, and that's probably still the case for current students. I tend to forget this myself, but "best possible" sound quality is not always the target.
What is a "narrow dispersion line array"?
So, the coupling that happens in a line array affects the vertical dispersion, presenting, at least at some frequencies, a wavefront that is more or less cylindrical in shape -- the surface of a section of a cylinder, of course, not a complete cylinder. The height of the cylinder is determined by the height of the array, but the section of the cylinder is determined by the characteristics of the components of the array.
In my Bose L1s, those components have a more or less 180 degree dispersion, which is unsuitable for a long hall. Speakers in general have dispersion ranging from about 15 degrees to about 180 degrees, so if you build a line array from something with a narrow dispersion, you can create something that works well with your particular hall.
A single speaker has a wave front that resembles a section of the surface of a sphere.
Dancing in a long line doesn't mean you get to dance with everyone. You only get to dance with as many couples as you meet before the music stops. Therefore, I have no idea why callers seem to like dancers to form short lines.
@Kiran: You know perfectly well that not all dances are symmetrical, that some callers think some of the asymmetrical dances are still worth doing, that callers (and many dancers) like to have different partners over the course of the dance, not just to dance with lots of different neighbors & opposites, and that callers in general prefer a larger number of shorter dances to a shorter number of longer dances over the course of the evening, though the ratio varies from caller to caller.
One really, really, long line that took the entire night to get through so that everyone could dance with everyone else in both roles while maintaining the same partner throughout, with a medley of dances and partner changes worked in might be an interesting experiment, but it's not what contra dancing *is* (currently).
It also wouldn't be a particularly new idea; it's something that contra dancing has evolved *away* from.
Yah, if you want insanely long dances, you know where to find the English dancers.