Array's Vs Cluster's

[Rob_Beech]

Alas, if only I could remember how to do that there Amazon thing, I could be helpful. It looks a good read, I might buy myself a copy for Christmas, but I'd sooner click on a link from here if it still works like that for the BR to get money from it.

[MarkPAman]

http://images-eu.amazon.com/images/P/0240520203.01.MZZZZZZZ.jpg

:unsure:

[Shez]

Be warned, it's not a light read... I'm only about a third of the way through after a couple of months and am struggling with some of it. (I'm also sure there are a couple of mistakes in there but don't think I'm really in a position to argue...)

[richie1575]

A quick question... can someone clarify what a "line array" is and what a "cluster" is and the supposed merits of each? I only do the light duty and Churchy stuff, but would be interested to know!

 

Thanks!

 

Richie

[MarkPAman]

This may help explain what a line array is. :unsure:

[Rob_Beech]

Oh come on mark, you could at least ....remind us how it's done :unsure:

[MarkPAman]

I'm only posting links today! ;)

 

It's about 2/3 way down. :unsure:

[Simon Lewis]

What the line array is tryng to achieve is an acoustic line source. Here, sound intensity is attenuated at a rate of 3dB per doubling of distance, whereas for a point source (which is effectively what a grouping or cluster of narrow dispersion boxes arrayed in a vertcal or horizontal pattern so as to minimise box to box interaction is trying to be) intensity tends to obey the inverse square law and sound attenuates at -6dB per doubling of distance.

 

Furthermore, in a line source, the horizontal dispersions tends to be the same as for a single element of the array, but the vertical dispersion tends towards a more parallel pattern. This gives good directivity control, but presents problems in actually covering the audience properly!

[mackerr]

Furthermore, in a line source, the horizontal dispersions tends to be the same as for a single element of the array, but the vertical dispersion tends towards a more parallel pattern. This gives good directivity control, but presents problems in actually covering the audience properly!

How does a line array present problems covering the audience properly?

 

Mac

[Simon Lewis]

How does a line array present problems covering the audience properly?

 

Mac,

 

If a line array is purely vertical, the dispersion may vary from parallel by only a small amount (say one degree). This may not be dispersion that's wanted to cover the audience area. Therefore, most manufacturers allow for some curvature, progressive curvature or J shaped arrays to increase the vertical dispersion - especially towards the front of the audience area. In truth, the listener at that point is likely to be hearing more of the individual element, rather than the full array, but that is OK because although the listener is outside of the main vertical lobe, he is closer to the loudspeaker and therefore the level tends to be comparable.

 

 

Simon

[peterejones]

The terms line array, curvilinear array and point source and theoretical models which we use to understand how sound propopgates from one or more sources. In real world apllications, the propogation characteristics may tend towards or approxomate the theoretical models. In almost all practical applications all three theories are relevant at different frequencies. i.e. a line array will tend towards a point source with decreasing frequency, whilst a line of omnidirectional speakers (eg subs) will tend towards a line source with increasing frequency. A distributed system may also be the best option when there are opportunities to place speakers in useful positions and directions to facilitate even coverage, in a correctly time alligned manner. To achieve good results it is important to understand the fundamental principles of source interaction at work within your system, have the experience to know how to apply these to best effect, and be fortunate enough to be using equipment designed with these theories in mind. Many systems designers will use components utilising line array, point source and distributed models, each in their appropritae situation to create the best solution for a particular brief.

 

Pete

[mackerr]

How does a line array present problems covering the audience properly?

If a line array is purely vertical, the dispersion may vary from parallel by only a small amount (say one degree). This may not be dispersion that's wanted to cover the audience area. Therefore, most manufacturers allow for some curvature, progressive curvature or J shaped arrays to increase the vertical dispersion - especially towards the front of the audience area. In truth, the listener at that point is likely to be hearing more of the individual element, rather than the full array, but that is OK because although the listener is outside of the main vertical lobe, he is closer to the loudspeaker and therefore the level tends to be comparable.

Since, in the many many events I have used line arrays in I have yet to see a straight one that wasn't a "column" speaker, what you're saying, and what I was as well, is that a line array does not present problems in covering the audience, but provides solutions that let you adjust the vertical coverage pattern to fit the venue. By creating a "J" array you also get the benefit of "divergence shading" to get more even SPL from front to back.

 

Mac

[J Pearce]

But by creating the J curve you compromise the 'line-source'-ness of the array.

[Rob_Beech]

Thus you are no better off SPL wise unless the point aimed at the back is a true line source (straight).

[mackerr]

But by creating the J curve you compromise the 'line-source'-ness of the array.

Thus you are no better off SPL wise unless the point aimed at the back is a true line source (straight).

The top of the array (which covers the back of the venue) is close to straight, and at the frequencies where the "line-source-ness" of the array matters, it is still pretty straight even at the bottom as the speaker displacement due to the curve is small relative to the wavelength.

 

Mac