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Author Topic: Sub Placement Question  (Read 2929 times)

Gordon Brinton

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Sub Placement Question
« on: March 23, 2017, 02:26:22 PM »

I really, really, really like to center cluster my subs, but those poor people in the front row are gonna get pounded. Where would you put them?

(The plastic over the seats won't be there. That's just for maintenance.)

2 top FOH boxes (1 ea. corner) will be on stands up on the stage, 2 side-fills pointed toward the wing seats, (1 ea. side,) and 1 center-fill on the stage lip up front. (5 in total, not counting subs.)

It's for a musical play and it's a very lively room. Volume probably won't be a concern, but coverage may be.
« Last Edit: March 23, 2017, 02:38:59 PM by Gordon Brinton »
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Stephen Kirby

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Re: Sub Placement Question
« Reply #1 on: March 23, 2017, 05:34:45 PM »

I've done a number of dance recitals in a slightly smaller but similarly arranged theater.  Single 18 on each wing.  The "cabin effect" seems to dominate and I don't find the holes on either side.  Maybe it's reflections from the sidewalls filling in.

At moderate volumes, combing from the other side is less of an issue.  Precedence of the near stack seems to overcome cancellation from something distant.
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Chris Grimshaw

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Re: Sub Placement Question
« Reply #2 on: March 23, 2017, 05:43:14 PM »

I'd probably co-locate with the main PA.

With live music where the audience might start 20' back from the PA, there's a bit of distance for a centre subs to sum with the mid-high section and everyone will get a balanced sound.
If some of the audience is right next to one bit of the PA or the other, they'll mostly hear that bit, resulting in either a lot of bass, or very little.

Remember 6dB per doubling of distance, and those first few feet really count.

Timing/phase errors pale into insignificance IMO if some seats will have the bass 18dB too hot (1m from the subs, 8m from the tops) and others have no bass at all.

Chris
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Stu McDoniel

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Re: Sub Placement Question
« Reply #3 on: March 23, 2017, 05:43:59 PM »

I really, really, really like to center cluster my subs, but those poor people in the front row are gonna get pounded. Where would you put them?

(The plastic over the seats won't be there. That's just for maintenance.)

2 top FOH boxes (1 ea. corner) will be on stands up on the stage, 2 side-fills pointed toward the wing seats, (1 ea. side,) and 1 center-fill on the stage lip up front. (5 in total, not counting subs.)

It's for a musical play and it's a very lively room. Volume probably won't be a concern, but coverage may be.
How much content will actually be in the subs under 80hz-100hz?  Place a sub on each side of the stage
with the tops and call it a day. 
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Gordon Brinton

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Re: Sub Placement Question
« Reply #4 on: March 23, 2017, 06:39:52 PM »

Well, three replies all for splitting the subs on each side of the stage with the tops. That's fairly convincing. I will indeed ponder it.

The stage is 70 feet wide, so there may not be much power alley if I keep their levels down. As Stu suggested, there may not be much content in the subs anyway. It's a musical play. The focus should be primarily on vocals and melody instruments, not kick drum and bass.

I ran a few plots to see my room coverage. (I could not plot low frequencies because my sub specs are not in the software yet.) For shits and giggles, I plotted at 400Hz, 1000Hz, 5000Hz, and 10000Hz. The room dimensions are not entirely accurate, but close enough to get a peek at what's going on.

I never plotted a room before, so I don't know if this is good or horrible. The first problem I see is that my highs are not getting to the back. They aren't expecting a full house, though.
« Last Edit: March 23, 2017, 07:07:40 PM by Gordon Brinton »
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Tim McCulloch

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Re: Sub Placement Question
« Reply #5 on: March 23, 2017, 07:52:54 PM »

70 feet?  Think about what frequency that represents... About 16 Hz.  Coupling and combing would be around 32Hz.

IOW you won't have a power alley problem in all likelihood.
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Stephen Kirby

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Re: Sub Placement Question
« Reply #6 on: March 23, 2017, 09:26:44 PM »

The first problem I see is that my highs are not getting to the back. They aren't expecting a full house, though.
So what happens is that people stay out of the seats to the side.  Which means you may be able to dispense with outfills or worry that much about coverage to the sides.  But people will tend to cluster along the centerline.
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Luke Geis

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Re: Sub Placement Question
« Reply #7 on: March 24, 2017, 08:11:41 PM »

I would also go with separated subs in this case. The aisle's in the front will be roughly where and sub cancellations would be most likely and evident, but that is the least of the problem. The subs in relation to the mains would be so far off that center located subs would be pointless. Experiment if you can, but subs under your mains seems to me the best way to go.
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Re: Sub Placement Question
« Reply #7 on: March 24, 2017, 08:11:41 PM »


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