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Author Topic: Line Array or not to Line Array  (Read 4509 times)

tunesmith

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Line Array or not to Line Array
« on: January 09, 2005, 03:07:42 pm »

Working with several sound contractors to get bids and information on our new sound system.

600 seat church worship arts center in a fan shape.  The building is 140' deep 140' wide.  We do all styles of music, from string quartet to contemporary band.  Two major drama musical productions per year.  We book artist in four times a year, all styles.

We are looking for the best concert quality sound we can get.  Money is not an obstacle.

Two of the contractors said because of the fan shape we needed a center cluster in mono.  They recommended Line Array w/ 18"subs.

Three contractors suggested a left right setting run in stereo.  Using 2 boxes per side with 12" & horn with a 18" sub on each side.  One said Line Array was over kill and should be used only for loud concert applications, not for clear sound.

Two Questions:
1. What is the correct application for a Line Array?
2. For a fan shaped theater should we ask for Left & right or Center cluster?

Thanks
Jim
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Rob Timmerman

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Re: Line Array or not to Line Array
« Reply #1 on: January 09, 2005, 09:36:22 pm »

If  money is no problem, and how wide your space is, I'd go for a LCR approach.  This gives you the best of the mono cluster and the best of left/right clusters.  As to whether a line array is appropriate, the only way to determine that is to model the space and the array.  It might be the best option, but there might also be better options.  I'd also look at getting an outside acoustical consultant, who won't be selling you equipment, to do the system design.
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Craig Leerman

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Re: Line Array or not to Line Array
« Reply #2 on: January 10, 2005, 02:50:16 am »

Quote:

 1. What is the correct application for a Line Array?
2. For a fan shaped theater should we ask for Left & right or Center cluster?


Because every individual venue presents its own unique acoustic challenges and requirements, no one system type is the right choice for all venues.

First, a line array is basically an assembly of specialized boxes hung one under another. The basic concept is that a line array will have a fixed horizontal dispersion and a narrow vertical dispersion. Most of these systems require a minimum number of boxes for the line array effect to work.  That could be a minimum of 4-6 or more boxes required hanging in a line.

A line array is not specific to live or loud audio, it is just a type of system that uses a line of boxes to achieve a specific coverage pattern.

Depending on ceiling height, and hang location, a line array may not work in a center cluster position.  Also, depending on the room width, and hang location, a center cluster line array may not cover all the audience areas.  Additional fill speakers may be needed.

A line array is not a be all-end all solution to PA problems, especially in installed venues.


As far as your building goes, the main questions to ask are:

<b>What rigging locations are available?</b>  Is it feasible to hang a large center cluster, or would the weight of a large PA have to be distributed across the ceiling

<b>What are the aesthetic considerations?</b> Will you be happy with visible  speaker clusters, or a long line array?  Will the speakers be covered or mounted behind a baffle? Will the weight of a baffle or other speaker hiding scrim make any location to heavy?

<b>Can additional fill speakers be used in the system?</b> Do all  the speakers need to fly from the ceiling, or can some smaller delays be mounted on wall, or under a balcony?

<b>Does the room height, or shape lend itself to one system type over another?</b> Is the room to short in height for a line array? Would a line array obstruct any sight-lines if used? Are their future plans for large Video screens, other A/V or Lighting that need to be addressed in the hang locations now?

<b>Is the room acoustically treated, or will additional acoustic treatment need to be made to use a large PA successfully?</b> Will the addition of a specific type of PA lesson any acoustic treatments required?

Then you need to ask the contractors who are bidding to show you successful uses of what they propose in similar sized/shaped rooms as yours.  This is very important, as it shows two things. One, that the proposed system type will fit your venue and needs. And two, that the contractor has experience in designing and installing these  type systems.

The biggest problem with most contractors is they they seem to recommend only what they sell.  If they only sell a limited number of brands, then you the customer may not be getting actually what you need.  a way around this is to use a Design consultant that is separate from the install contractor. Have the  consultant design the best rig for the space, and then shop out his specs to installers.  That way you are not limited to only what brands an installer has.

As for me, the perfect installed system is one that provides adequate coverage to all audience areas, without putting more wasted energy into the rooms.  

I would think that for your wide fan shaped room that a system of controlled dispersion boxes (like SPLs TD1s or Runts) or similar in a central cluster or Left/Center/Right clusters would fit the bill better than just slapping a few line arrays in.  Additional subs could be flown or placed at the ground level (or even hidden under the stage, in walls, etc)

Oh, and one last thing, bigger is not always better.  Many contractors spec an 18" subwoofer because they think that a larger cone or bigger box will provide better bass. That is far from the truth.  Our LAB Subwoofer project right here on PSW uses 12" drivers, and outperforms just about every double 18" cabinet.    There are a lot of subwoofer systems that are way better suited to installs than large bulky  18" boxes.

Meyer, and others have cardioid subwoofer. These cardioid subs focus their energy to the front, less energy to the sides, and even less energy still to the rear. This results in less bass leaking into areas where you don't want it (like on stage) and not bouncing off walls or other reflective surfaces.  

In addition to cardioid subs, many manufacturers have subs with other pattern control and directivity.  Some subs are small and can fly, while others may be large, but could be built into the building (like under the stage) so they are not visually apparent.

Craig Leerman

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I'm so old, when I was doing FOH for Tommy Dorsey, to balance out the horn section I would slide their chairs downstage and upstage to mix!


Tom Young

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Re: Line Array or not to Line Array
« Reply #3 on: January 10, 2005, 06:10:49 am »

The 2 posts that precede mine are very informative.  I would add that:

1)  because of the very tight vertical pattern from a line array, it is paramount that their aiming and the orientation and  construction of the rear wall be very carefully considered.

2) it is generally considered that any cluster needs to cover all of the room. Obviously this would be the case for a mono center cluster. For L,R clusters and L,C,R clusers this is also true.  Without this the spacial experience is lost for many and they will not hear wide-panned sources.

3) technologies such as Bag End's ELF system are another method for getting deep subwoofer energy without the need for large drivers *and* large boxes.

4) one more reason to hire a qualified consultant is optimization.  Many contractors (and some consultants) do not take the time or do not know how to measure with complex measurement systems followed by soundchecks and further tweaks when the congregation is present. This needs to be followed by operator training in many cases.

So; you have solicited 5 proposals and the results are confusing. It is time to hire an independent design consultant who will be employed to provide a working system that meets your specific needs. This may include acoustic treatment of the sanctuary and the platform.
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Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com

Craig Leerman

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Re: Line Array or not to Line Array
« Reply #4 on: January 11, 2005, 07:09:26 am »

Tom added some more good points.  I have one more I forgot to mention.

Stereo is not necessarily "better" than a mono system when it comes to live audio.  While each system has its own benefits and limitations, a satisfying live audio experience can be had with a MONO center cluster rig, A STEREO or MONO Left and Right speaker rig, or a Left/Center/Right speaker placement rig.  All three type of systems can be used to great success when properly designed and installed.

Craig  

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Phil Ouellette

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Re: Line Array or not to Line Array
« Reply #5 on: January 12, 2005, 05:44:43 pm »

Craig Leerman wrote on Tue, 11 January 2005 07:09

Tom added some more good points.  I have one more I forgot to mention.

Stereo is not necessarily "better" than a mono system when it comes to live audio.  While each system has its own benefits and limitations, a satisfying live audio experience can be had with a MONO center cluster rig, A STEREO or MONO Left and Right speaker rig, or a Left/Center/Right speaker placement rig.  All three type of systems can be used to great success when properly designed and installed.

Craig  




To be specific, a central mono system is better for the spoken voice than a left/right mono or left/right stereo system.  For music, the stereo system is better (assuming the entire audience is covered from both left and right clusters).  The biggest advantage of a left/center/right system is that you can pan your mono sources to the center cluster and your stereo sources can make use the left and right clusters which gives you the best of both worlds.

Phil
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