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I'm running live sound for an event that takes place in a 100'x100' building. The walls are pretty thin, floors are concrete, ceiling is arched and probably 25-35' at highest point.

I will probably be using 3-4 SRM450's for the mains setup mono. Seating for 600 people, but they're fairly spread out in the front 3/4's of the room.

My question is this: What should the subs look like?

Specifically:

  1. How many
  2. How big (15", 18", etc)
  3. How much power
  4. Where should I place them

Main genre is rock. We've previously used a Mackie SWA1501 + QSC HPR151W, but it felt underpowered.

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I suspect you're going to find your SRM450s quite under-powered for the genre and crowd as well. I use a pair of 400W bi-amped powered speakers with a pair of powered 1000W 18" subs, and couldn't imagine using this rig for a crowd of more than 150 or so in a similarly sized space. Of course, sub-wise, that would be fine for rock. –  Brad Sep 22 '11 at 20:06
    
We've done it several years now, and while the SRM450's do leave a lot to be desired, they're adequate - I'm interested in a sub setup that matches the SRM450's, though they are certainly not ideal themselves. "Rock" probably isn't the best genre description. –  Mike Riess Sep 25 '11 at 6:59
    
Back in the day when we carried our entire backline we used to use about 12kW for halls like that, with four 4x18 cabs for bass. And that band just played rock covers (Bon Jovi etc) –  Rory Alsop Mar 14 '12 at 23:26
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1 Answer 1

We've got a PA setup for DJing events, and we use a single Behringer B1800D-Pro alongside 2 Alto Professional 15's (800 watts each). The biggest problem we have is getting even bass throughout our venues. The Behringer pounds behind the table, and in certain areas in the venue, but sounds weak in others. Your room is much bigger than what we would do use our system in, but I suspect getting the bass to be evenly distributed is going to be a challenge for you as well.

Sorry for the bad news, but acoustically, your venue is a nightmare. Square rooms create really strong resonances, and the concrete floor won't help. However, a good EQ will do a lot of good.

As for the subs, I hear that folded horn subs provide great SPL and distribution. I would recommend 4 subs (18") at about 1000W each. I have not done a venue this big before, but consider it an educated guess.

As for placement, consider placing them in two pairs at the back of the stage at thirds of the room dimension (33ft and 67ft) for acoustic coupling. This is constructive interference of the sound waves that happens when you place two identical subs next to each other. If that doesn't sound even in the room, break up the pairs and disperse the 4 evenly across the back of the stage.

At my church they place the subs down in front of the stage on the floor, and that works out very well, but it may not work with your particular needs in terms of space. It's worth a try.

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