AdubsDJService
Good evening BASSBOSS family!

Referring to line arrays. 

How many line array boxes does it take before the advantages of line arrays start? (3 or more?)
Do the size of the boxes being used play a role in when the line array technology starts to work? (think LA88 vs MFLA)

Can/should line array boxes be used in every situation? 

When would it be advantageous to use a point source (AT212) over a line array (MFLA)?

When would it be advantageous (reverse the above statement)?

Looking forward,
Adubs
Gear List: 2x AT212 | 2x DV12 | 2 DV8 | 4x ZV28 | 2x VS21
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nmineau
This is a tricky question, but ill try. How tall the array needs to be to act as a line source depends on the frequency at which you want the line source to control the dispersion pattern in the vertical axis. you will get good line array behavior at 2x the wavelength of the lowest frequency you want to control. If you want to control frequency's only above 500hz, for say a tornado alarm warning system for a hole town, and don't care about what it sounds like under the array, then a 4ft tall array of old stacked bi-radial horns with some old 1980's peavey x22 compression drivers on the back of them will offer the vertical control, spl, and throw desired from a line array, you'll hear it 5 miles away, and wont deathen people right under the array because the vertical coverage is so narrow. just don't expect anything under 500hz lol..  However if you want to control down to 100hz in the same way, your looking at a 22ft line of woofers, that sounds easy until you realize the hf horns in these cabs are also stacked 22ft tall!!  which means you'll need horn lenses with a basically 0 degree vertical coverage, so you can curve the cabinets themselves to aim each hf horn to a appropriate area in the audience.. and you will then have to gain shade them, so you don't kill the first few rows!  So you have to ask yourself, do I even want that much vertical control? Do I need vertical control at all in lower frequency's? Do I need the extra throw offered by a line array setup? Maybe you just need the control from 1khz up to keep things of the ceiling and floor in a space that's not very long, which means you can get away with a really nice horn lense and single compression driver, and not have to deal with splaying the cabs just right to widen the narrow vertical coverage you worked so hard to get in the first place.. in this case, a point source is better. If you need to throw sound 200ft or more, you'll need that control up close to the stage so you don't hurt people w spl.
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Glen Allan

Hey Adubs,

There are few things to consider when thinking about line arrays, but the most obvious i can think about offhand regards reach and dispersion. The wave-guide in line arrays changes the way the pressure wave focuses the energy, generally to make it narrow on the vertical and very wide on the horizontal. This does a couple of things. It makes it so the loudspeaker can be heard from much further back, and allows for wide dispersion without the tendency of multiple boxes to create phase problems.

What makes it a line array is that any more than one box, when they are connected together, act as a single source. So even with the DV12, you can take a second one and invert it above and you will already have a line-array "effect". The two boxes effectively become one and maintain phase coherence through the vertical alignment of the waveguides. That's part of why the DV12s have the kind of isophasic waveguide they do. If you think about it, in a sense 2 DV12s is the same thing as 1 MFLA. The obvious difference being that the lower frequency drivers are not entirely in phase during coupling of the DV12s. The MFLA in just one box already takes advantage of the line-array effect with the two waveguides mounted vertically stacked. The number of speakers helps more with that directionality and vertical coverage, at least down to a range of frequencies. The LA88 & MFLA are designed for much better coupling through their entire frequency range, but the more directionality you want for the lowest frequencies they cover, the more boxes help.

My argument would be that you'd want to move to a line-array as soon as you need a large distance to cover. While the AT212s can be grouped to increase output more or less effectively at a short to medium distance, the further out you go the more you'll see the effects of filter combing and end up with nulls and sums in the crowd. And because they throw out their energy in 80° x 60° vs 120° x 10° or 140° x 8° (for the MFLA & LA88), a decent about of the energy output is lost above and below. Using the inverse square law you end up finding the phase issues getting worse the further back, along with all the vertical top and bottom energy totally lost at distance. This might be mitigated somewhat indoors as you'd have reflections and all that both hurting and helping, but definitely outdoors having a line-array source would help to mitigate having anywhere near as much an issue with phase and output in the crowd.

David can give the best info of course, so hopefully he'll chime in!

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