theatre stage question / vibrations from bass frequencies

[Crimson Chameleon]

A high school where I frequently supply teach at, recently got a large screen for their stage in the auditorium. I believe the screen is called a scrim: it hangs at the back of the stage and can be used to project images and colours for stage sets.

This afternoon the principal hung a projector above the front of the stage, and attached it to a bar that also suspends two full-range speakers. The concern is that when music is playing, the vibrations from the bass frequencies will shake the projector thereby causing the image projected onto the scrim to move.

They asked me what I thought about it and I said there is no way for me to know how bad it will be without trying. So we will likely do a few soundchecks this week to see what happens.

One thought we had is that the two speakers, which are currently centered on the bar, could be moved further apart to the outside edges of each side of the bar. Would that have any effect?

We'll probably do some experiments, but in the meantime, I figured I would see if anyone on the forum has any experience with any situations like this, or any suggestions.

[Malcolm Boyce]

My instinct says highly doubtful you'd see any issue with the video because of the PA being attached. If the projector is properly rigged, it should be solid enough to avoid any "audio" related interference.

Any chance of pics?

When you say relocate the speakers, I hope you don't mean mess up a working sound install to make a new projector work, and mess up the audio quality in the room for visuals... because although unfortunate, it wouldn't surprise me at all. I've seen it many times.

[macrae11]

+1

[Crimson Chameleon]

Thanks guys!

Hopefully we won't need to move anything. And if for some reason we do, I'll make sure I suggest relocating the projector before messing with the sound system!

I'll let you know how the soundchecks go; and I'll post pictures if I can get some.

[Jerkyman]

Yes, pictures would be an excellent idea. Are the speakers attached directly to the pipe or do they hang on wires? What size speakers are they? Can you feel bass from them? If not you will not likely have an issue, especially if they are on wires.
P.S. - I believe you have a cyc for a screen unless you can see through it like a screen, then it would be a scrim.

Cheers!

[warrbeat]

P.S. - I believe you have a cyc for a screen unless you can see through it like a screen, then it would be a scrim.


Sorry Jerkyman but I gotta...

If it's a cyc, it'll rip...it's a scrim Al can walk through it...