Speaker needs per room size

[CavezziMagnum]

Hey there,

I am mainly a lighting technician, but recently i've gotten into working with my friend who DJs. I was wondering if anyone knew if there was a rule on how many watts or the size speakers that are necessary to produce a certain kind of effect for evert 10' or 20', whatever.

Specifically, I am working in a rom 60' x 80' with a triangular roof at the peak is 30' and the walls are 20'. Most importantly, the walls are made of aluminum or tin sheets (the stuff you would use as a sound effect for thunder), so I know there will be major reverberation.

Any suggestions would be really helpful. Thanks!

 

[howlingwolf487]

WARNING: Stereotype Ahead

If your friend is the typical DJ, loud is really all that matters, gain structure means nothing, and his/her feed will always need to be turned up more to compensate for their going deaf.

END STEREOTYPE

Before anyone gets on my case about assumptions, etc., let me clarify: I don't feel your friend actually IS this way. The potential is there to go either way (the DJ who just wants it louder or the DJ who understands the system they are running)

Now that that's out of the way...

A system of main speakers, along with some delay speakers placed accordingly, would help keep the dB's down and the even coverage up.

That being said, our touring rig at my university uses 4 Mackie SA1251z's and 4 of their 15" subwoofer counterparts. It can cover our 697-seat auditorium nicely. A similar setup would work just as well, I assume.

I can tell you is that as the amount of people increases, the amount of gear (and the cost of that gear) increases exponentially. Buy once, cry once. Make sure your friend gets some good references on gear. If you know anyone who has been doing sound for a long time - preferably in a more professional context - point them that way. Tell them to read up on gain structure and learn what "clipping" is and why it destroys speakers.

 

[waynehoskins]

The answer is, of course, "it depends".

The most basic rule of thumb I know is that your subs will usually eat up 4 to 10 times the power of your tops. If I've got a MT600 driving the left tops, I probably want a MT2400 driving the left subs, and I want the subs to be able to handle that power.

But it's all about coverage. Cover the room right, put the right amount of amplifier behind it (which for me is matching ratings; other guys use other techniques).

I haven't found a situation yet, in a small venue at least, where I needed or wanted more than 300 watts per top and a couple of KW per sub. That seems to do the trick well enough. Goodness, at the church, that's the PA turned up to Eleven, and it rocks at Eleven. Never measured with a SPL-meter, but it's over 100 at the back wall, no question.

But everything in sound is so relative, and sometimes trivial, so again: it depends.