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Author Topic: Line array or conventional cabinet for 'gymatorium'?  (Read 5077 times)

Pete Bansen

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Line array or conventional cabinet for 'gymatorium'?
« on: August 21, 2013, 04:56:51 pm »

List -

I'm working on a committee to do lighting and sound upgrades in a community arts center.  The performance space is basically a gymnasium with a stage at one end - the gym is a little larger than the size of a standard basketball court.  The stage is centered in one end of the room with about 8 feet of wall space on each side of the "molding" that frames the proscenium opening - the stage is about 40" above the floor of the seating area.  Flat, hardwood floor, flat ceiling (although high - probably 24') and flat walls surrounding the rectangular audience space.  It's an older building and I have done a number of shows in it using "speaker on a stick" configurations (sometimes with subs, sometimes without).  The acoustics of the room are surprising good.

The sound upgrade is intended to serve a variety of uses: everything from a speaker making a presentation to acoustic music to kids plays and amateur musicals.  We have a proposal from a reputable vendor for an audio system using two JBL VRX932LAP line array speakers (presumably flown one to a side flanking the stage) and a pair of PRX718-XLF subs.  I have no problem with the subs - I'm sure those would be fine - what I'm wondering about is the use of a single line array cab on each side.  Horizontal coverage won't be a problem, but I wonder about covering an audience adequately from front to back with a single speaker on each side, even if it is carefully oriented for maximum coverage.  It doesn't seem like a situation where the advantages afforded by the line array concept are either needed or can be utilized with a single cabinet and that we would be better off with a single, high quality conventional cabinet hung on each side of the stage. 

I have worked with line arrays very little and I'm admittedly out of my element, but I suspect we'd be better served with cabinets with broader vertical patterns, given that the very limited budget will only buy one cabinet per side. 

Thank you in advance for your input!
« Last Edit: August 21, 2013, 05:11:55 pm by Pete Bansen »
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g'bye, Dick Rees

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #1 on: August 21, 2013, 05:37:15 pm »

I'm with you in thinking that those JBL's are going to excite the reverberant field and make mud like a rainstorm at a ballgame.

Whoever is putting in proposals should be required to do a coverage prediction IN 3Dimensions.  That and a demonstration.
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Tom Young

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #2 on: August 21, 2013, 05:43:22 pm »

I have worked with line arrays very little and I'm admittedly out of my element, but I suspect we'd be better served with cabinets with broader vertical patterns, given that the very limited budget will only buy one cabinet per side. 

You are correct. This is not the right device for this space.

With 15-degree vertical coverage each VRX will have to be mounted fairly low in elevation to cover from near seats to the rear of the space. Among other potential problems with this is that the SPL up close will need to be loud in order for the SPL at the rear to be sufficient.

A better choice would be a point-source loudspeaker in the 40-60 -degree vertical range. Mount these (1 per side) up fairly high (30'-35') and aim them down so the seats are covered. At this height the distance from ldspkr to seating, both at the front and back, will be much more equal and therefore more even in level. Also due to mounting height; any energy which strikes the walls will be reflected downwards, absorbed by audience and seating.
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Rob Spence

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #3 on: August 21, 2013, 07:56:59 pm »

You need to know the real ceiling height. If 24' then cannot fly at 30'.
Don't guess.
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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #4 on: August 21, 2013, 08:05:27 pm »

You need to know the real ceiling height. If 24' then cannot fly at 30'.
Don't guess.
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Rob...

I took Tom's statement of height to be as he said "fairly high" and as such a definition of "fairly high" rather than an absolute height requirement.  Let's just go with AHAP.

Sent from my couch watching "Numb3rs" on broadcast TV.
« Last Edit: August 21, 2013, 08:17:25 pm by dick rees »
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Rob Spence

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #5 on: August 21, 2013, 08:16:06 pm »

Rob...

I took Tom's statement of height to be as he said "fairly high" and as such a definition of "fairly high" rather than an absolute height requirement.  Let's just go with AHAP.

Sent from my couch watching "Numbers" on broadcast TV.

I only mentioned it cause I have seen dozens of posts over the years that guessed at the height and then later came back with a much different number that changed the conversation.


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Ivan Beaver

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #6 on: August 21, 2013, 08:23:49 pm »

One element does not make a line array.  It makes a box that has a very narrow vertical pattern at the higher freq-that is all.

You say the budget will "only buy one box per side"  So that is a specific amount? or they will only let you buy one box per side-no matter the cost?  You can get a "point source" that has more vertical coverage (there for more even front to back for the high freq that will work better.

The whole idea is to use the right tool-not part of a tool-that you don't understand how it works.

Whatever system you choose-be sure to ask the "designer" for a coverage map-AT A NUMBER OF FREQ (say 500-2K 8K and maybe some inbetween).

see how smooth they are.  Of course there are all kinds of ways to make a horrible coverage actually look OK-by means of smoothing-plot size etc. so you REALLY have to be careful what you are looking at-and NOT just the pretty colors-of course it is best if there is only ONE color :)

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Tom Young

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #7 on: August 21, 2013, 09:00:19 pm »

Rob.......I took Tom's statement of height to be as he said "fairly high" and as such a definition of "fairly high" rather than an absolute height requirement.  Let's just go with AHAP

I should have re-read the OP. I *did* get the height wrong. Assuming the OP got it right  ::)

AHAP works until we have a more defined/confirmed working height.
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Pete Bansen

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #8 on: August 21, 2013, 09:05:43 pm »

One element does not make a line array.  It makes a box that has a very narrow vertical pattern at the higher freq-that is all.

I get that part, that's why my post refers to 'line array speaker' and 'line array cabinet'.  If there's only one, it's not an "array"

You say the budget will "only buy one box per side"  So that is a specific amount? or they will only let you buy one box per side-no matter the cost?  You can get a "point source" that has more vertical coverage (there for more even front to back for the high freq that will work better.

The whole idea is to use the right tool-not part of a tool-that you don't understand how it works.

No, no - the budget has some flex in it, but probably not enough for two or three of the VRX932 cabinets per side, which is what my back of the envelope plot makes it look like what would be needed. 

I'll get an exact ceiling height measurement, but generally - as a point of education for me (and no doubt others here...) - does this sound to those of you for whom line arrays are bread and butter like it's a situation where a properly configured line array system would have significant advantages over a quality point source system?   I throw the 'significant advantages' caveat in there because the price difference is very significant.

From what I'm reading in your responses, it sounds like I have a better understanding of how this tool is supposed to work than the vendor...

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Ivan Beaver

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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #9 on: August 21, 2013, 09:36:06 pm »

I get that part, that's why my post refers to 'line array speaker' and 'line array cabinet'.  If there's only one, it's not an "array"

No, no - the budget has some flex in it, but probably not enough for two or three of the VRX932 cabinets per side, which is what my back of the envelope plot makes it look like what would be needed. 

I'll get an exact ceiling height measurement, but generally - as a point of education for me (and no doubt others here...) - does this sound to those of you for whom line arrays are bread and butter like it's a situation where a properly configured line array system would have significant advantages over a quality point source system?   I throw the 'significant advantages' caveat in there because the price difference is very significant.

From what I'm reading in your responses, it sounds like I have a better understanding of how this tool is supposed to work than the vendor...
I will probably get in trouble for this-but I would argue that a large percentage of "line array" users have no idea why they "think" it is "better".

I say this based on the following assumption.

I bet if you asked the average person why a line array is "better" you will get the following:  "Well it only drops off at 3dB vs 6dB of doubling distance".  But yet they can't give any idea of how that is freq dependant or even what that means. 

Just look at the number of posts that want to use a very few number of boxes or a couple of "mini" line arrays.

Just ask them why they think a "mini line array" is good and you will probably get a response like- " Well 8 of the large boxes are to expensive-so I can get 8 of the smaller boxes for less".

Yet once again proving they have no idea how the PHYSICAL SIZE OF THE ARRAY is important to get the 3dB "effect".

And they are willing to accept the loss of sound quality (due to the interference) and the issues it causes when the wind blows (of course outside) because it "is popular" or "looks cool".

Of course the same people have never actually DESIGNED a sound system properly.  If they had-they would realize real quick a point source is fully capable of having ZERO difference in SPL from the front row to the back-TOTALLY defeating their concept of "a line array has better coverage than a point source". 

But that would require knowledge and thought-usually which get overlooked because the line array "looks sexier".

OK now we are getting to the real "crux" of the matter.

Time to stop  before I piss off to many people.

Sometimes the truth hurts.
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Re: Line array or conventional cabinet for 'gymatorium'?
« Reply #9 on: August 21, 2013, 09:36:06 pm »


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