01-22-2013 09:11 AM - edited 01-22-2013 09:13 AM
I thought I'd share THIS article about line arrays. I'd read it in the past, came across it the other day and was reminded what a good article it was. It's written in layman's terms yet gives some depth on the technical aspects of a line array. I particularly like the "highway noise" example.
Also well done is the explanation that the physical array needs to be 4x the wavelength to exibit true line array properties of -3db fall off for every doubling of distance. I did some math with my litlte column speaker and it works out that I'm getting some of the aspects of an array at around 2000K, which agrees with the published specs.
Anyway just thought I'd share.
01-22-2013 09:45 AM
Agreed. It's over-simplified as there are a number of excellent solutions that fall between the conical "marketably ideal" line source and the vertical summation benefits of a number of spherical section devices that have been designed for controlled off axis response. There are two distinct paths that a designer can take with regard to this, both have strengths and weaknesses. Often a hybrid approach works best (with minimum negative artifacts).
01-22-2013 01:36 PM
Add this to it ...
Can a Line Array Form Cylindrical Waves?
In a word, no.
The common misconception regarding line arrays is that they somehow magically enable sound waves to combine, forming a single "cylindrical wave" with special propagation characteristics. Under linear acoustic theory, however, this is impossible: the claim is not science but a marketing ploy. - John Meyer
01-22-2013 01:51 PM
IMO, this is a partial "theoretical truth" and partial practical myth. Where the vertical dispersion changes at a lower rate than the horizontal dispersion is what's responsible for the majority of what happens within the critical distance. In practice it's impossible to get a true cylindrical crossection but you can get a crossection that expands at say 90 degrees in the horizontal direction and say 15-20 degrees in the vertical direction and you will get some practical benefit. Not as much as the theory (and thus the marketing) suggests but maybe you will get a practical 4dB per doubling rather than 6dB per doubling that a point source would end up being.
Also, all of this varies somewhat with frequency, so there is no single exact number anyway.
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