On 03/20/2011 04:52 PM, Fons Adriaensen wrote:
On Sun, Mar 20, 2011 at 11:21:41AM +0100, Jörn Nettingsmeier wrote:
What is this 'coupling' ?
just a frequently used technical term used by p.a. systems engineers to
describe the plain simple fact that a reasonably high number of point
sources reasonably close together will begin to resemble a line source
for a limited frequency range over a limited distance, with the
associated advantages for directivity and throw. aka huygens' principle.
no magic whatsoever, and no non-linearities required.
the trick with line arrays is to know for which bands you can exploit
which tricks. the superposition model tends to work well for the low and
midrange (provided you use sufficiently long arrays), and you fix the hf
response (which is indeed made of individual narrow beams) by gracious
application of eq, by splaying the array, and by driving portions of the
array with slightly different signals.
so a downfill extension, which has much wider vertical coverage to fix
the FR for people close to the stage, will still be part of the
effective line length for lower frequencies.
btw, it is not strictly true that you splay the array to emulate a more
distant point source. arrays are almost never splayed along a circular
section. usually, the main part retains a strictly linear shape (which
will usually be tilted down as a whole), and you only curve the lower
part, to fill in the closer range, resulting in the well-known "J"
shape. hf directivity is usually reduced for the downfills (25° vs. 5°
is not an uncommon figure), and you usually eq them differently and
sometimes reduce their output power to ensure uniform coverage,
depending on the height of the available anchor points.
--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT
http://stackingdwarves.net
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