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Author Topic: Whats the difference between a line array and trap cabinets hung sideways?  (Read 8367 times)

tim.j.phillips

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So I was curious:
I've heard some people talk about how various cabinets, while they look like line arrays and can be flown like them, are not true line arrays.  For example, the JBL VRX i've heard some people say are not true line arrays because the focal point, at 15 degrees i think, is not small enough to focus.

So how do you tell the difference between a true line array and trap cabinets that are just hung sideways?  Is it just a matter of vertical coverage or a mixture of different variables?
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Gordon Brinton

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I understand that the difference is mainly in the lens design for the horns. Conventional horn lenses do not interact well when placed too close together. A newer waveguide design helps correct that problem.

Check out this description at the QSC site.
http://www.qscaudio.com/support/education/designing_line_arrays/index.php?b=part1&p=2

Line array waveguides are very narrow vertically, but have a wide horizontal dispersion pattern.
« Last Edit: April 01, 2011, 06:45:43 AM by Gordon A. Brinton »
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Bob Leonard

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So I was curious:
I've heard some people talk about how various cabinets, while they look like line arrays and can be flown like them, are not true line arrays.  For example, the JBL VRX i've heard some people say are not true line arrays because the focal point, at 15 degrees i think, is not small enough to focus.

So how do you tell the difference between a true line array and trap cabinets that are just hung sideways?  Is it just a matter of vertical coverage or a mixture of different variables?

There is no simple answer to a complex subject. Read this;
 
http://en.wikipedia.org/wiki/Line_array
 
 
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Brad Weber

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I've heard some people talk about how various cabinets, while they look like line arrays and can be flown like them, are not true line arrays.  For example, the JBL VRX i've heard some people say are not true line arrays because the focal point, at 15 degrees i think, is not small enough to focus.
The simple answer may be the difference between a box intended to have a one box covering an area versus a box designed to allow one or more boxes covering the same area and interacting in a desired and predictable manner.
 
Just being a vertical array does not define being a line array.  The VRX is a good example as it is a constant curvature array, it is a vertical array of boxes but with each box addressing a fixed vertical coverage and the number of boxes defining the overall vertical pattern of the array.  In comparison, in a line array the number of boxes affects the overall vertical pattern and/or variations within that pattern, you have multiple boxes with varying degrees of overlapping coverage in order to increase the output at points within the overall vertical coverage and/or to increase the overall vertical coverage.
 
So with an array like the VRX you have a defined vertical pattern with the number of boxes times then nominal pattern per box defining the overall vertical pattern.  With a line array, the number of boxes does not necessarily relate to the overall vertical coverage but to both the overall coverage and variations within that coverage, one has to look at the specifics of the relationships between devices within the array to assess the resulting pattern and coverage.  Boxes made for line arrays should allow that result to be more useful and predictable, boxes not designed for the purpose may interact in some undesired and less predicatble manner.
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Bennett Prescott

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Keith Broughton

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Great article Bennett!
There are a number of people I know that should read it.
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Dave Bigelow

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Oh, I remember that article, quite a good read. Pretty sure I pulled it out at work and forced it on everybody.
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Steven Leonard

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This article may help, a little.

http://www.soundforums.net/content/148-Loudspeaker-Misconceptions

I know this is an old thread but I came across it after a search and I have to give props to Bennett on this fantastic article. Great Read!
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James A. Griffin

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For example, the JBL VRX i've heard some people say are not true line arrays because the focal point, at 15 degrees i think, is not small enough to focus.

Note that JBL refers to VRX as a "constant curvature array".    Users and others tend to call them "line array"  as a shorthand, though they are actually not.
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Ivan Beaver

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Note that JBL refers to VRX as a "constant curvature array".    Users and others tend to call them "line array"  as a shorthand, though they are actually not.
Do you mean like most cabinets that are called "point sources" are not also?

A line system is a long device that has the devices very close together.  Such as a very tall ribbon.

A point source is a device in which the sound comes from a single point-most so called "point sources" do not have this arrangement.  When the different bandpass devices are seperated-they are not acting as a "point".

Of course a line source is infinatly long and a point source is infinately small-but in the real world these don't exist.

I bet if you asked most people why  they think a line source is better than a point source-they would not be able to give an accurate answer.  Or the answer would be full of all sorts of assumptions and errors.

The same thing for a point source.

When one starts to understand the differences-it becomes quickly apparent that the real world is quite different than the "theory" states.
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