Learning about small-scale line arrays

[back_ache]

I am interested in learning about the contentious issue of small scale line arrays, as customers in small venues doing live music are beginning to show interest in them.

 

So with my flame proof hat on, I am wondering does anyone any experience in these, in particular EV's EVA system (which aims to reduce the number of amps needed)?

 

I have been hunting around the web but only found reviews that are tied in with manufacturers and people arguing on forums.

 

I would like to find some independent hands on knowledge about what does "what it says on the tin" and what doesn't, especially as it seems it is arguable with some of them whether they are actually arraying at all.

[csg]

I own and operate a Void Acoustics Arcline 6 small format line array, which I added to my hire stock approx. 18 months ago.

 

It has proven a very popular and busy system, and has proven itself to be a very versatile system.

 

However, there are several points worth noting when considering a small "line array".

 

I think many of us are aware that for a line source to operate as a line source at any given frequency, the length of the source is critical. This is a physical law and can not be beaten by any kind of marketing. Typical short arrays only operate as a line source at mid and high frequencies, lower frequencies reverting to decay as per the inverse square law.

 

I prefer to view small line arrays as neat, easily scalable systems that produce point source performance with a good degree of vertical dispersion control, a lack of destructive / constructive interference ( combing) issues, whilst at the same time reducing typical truck pack sizes and simplifying rigging.

That is all well and good as long as you remember that you loose a degree of horizontal dispersion control that you would have with a point source array.

 

So, all in all, I would say that small array systems are well worth looking at, so long as you are not expecting to get the extended throw that full range length arrays will achieve.

 

Finally, I would bring your attention to rigging. There are a wide variety of small scale array systems on the market. Some are more versatile in the way that can be rigged or operated than others.

A big part of my decision to go with the Void Arcline system came from the fact that it is possible to stand mount / fly / ground stack the system, which makes it a practical prospect for many different events.

If decent results can only be gained from flying, then naturally the list of suitable applications will shrink.

[Simon Lewis]

... especially as it seems it is arguable with some of them whether they are actually arraying at all.

 

When the frequency decreases, they move away from arraying (i.e. from being within (say) 1/2 wavelength) to lobing.

[Simon Lewis]

Sorry, let me get that right... it should read when the frequency increases I.e when the distance between sources is 'large' compared to the wavelength, lobing occurs - so either interdriver spacing is too big or the wavelength being reproduced is too small. Furthermore, the (LF) directivity of the vertical array will be larely determined by its length.

[back_ache]

the length of the source is critical

 

How many mid/top boxes do you find you have to have in a hang for it to start to act as a line array?

[Doug Siddons]

I use HK Contour array, in answer to you question about using small line arrays in small rooms for bands here is a picture of a 4 box system in a room for 150 people.

 

Practically it worked very well, was it working as a line source or point source debatable but it filled the room.

 

http://i160.photobucket.com/albums/t179/butcombe/Summer%20pics/rigatpilton.jpg

[Simon Lewis]

How many mid/top boxes do you find you have to have in a hang for it to start to act as a line array?

It depends... but this paper has some good guidance

[TonyMitchell]

Excuse what will probably be basic to those with Line Array experience, but here goes...

 

Taking an example similar to Doug's (above), where the hang is so short it is not operating as a line source throughout the operational frequency, what advantages are there in using say three boxes with 15 degree vertical dispertion, as opposed to one box with 45 degree vertical dispertion?

 

Other than a wider horizontal pattern, which going back to Doug's photo, with a single 70deg(h) box, one would typically turn the MHF boxes in toward the dancefloor, is there any other reason to go for the multiple narrow vertical boxes in this type of setup?

 

Tony

[csg]

the length of the source is critical

 

How many mid/top boxes do you find you have to have in a hang for it to start to act as a line array?

 

Well, for the array to start exhibiting the main desirable attribute of a line source - throw, with my system I should say that a 4 long hang / stack is the starting point. This seems to produce good consistent results out to 40m.

The elements in my array are approx. 450mm wide, so that would give an array length of 1.8m.

 

As the array gets longer, the lower the frequency that throws well. At 6 or 8 boxes, the array really becomes alive and comes together nicely in the lower mid / upper bass area.

 

Simon brought up an interesting point re high frequency limits - many arrays, particularly some of the cheaper offerings have high frequency waveguides with gaps that are too big to support the highest frequencies. This effectively limits the high frequency performance of the system, and its one area you should pay particular attention to, when considering different systems.

[nb705]

Excuse what will probably be basic to those with Line Array experience, but here goes...

 

Taking an example similar to Doug's (above), where the hang is so short it is not operating as a line source throughout the operational frequency, what advantages are there in using say three boxes with 15 degree vertical dispertion, as opposed to one box with 45 degree vertical dispertion?

 

Other than a wider horizontal pattern, which going back to Doug's photo, with a single 70deg(h) box, one would typically turn the MHF boxes in toward the dancefloor, is there any other reason to go for the multiple narrow vertical boxes in this type of setup?

 

Tony

 

 

Because then you can say to your client that you are using a line array. In a situation like the one you've described, that is pretty much the sole advantage.

[Ambrose Thompson]

Hello,

 

You may find it interesting to perform some simulations of small arrays in the new (free) EASE Focus 2. It comes with two types of generic line array which are reasonable approximations to many of the boxes out there. Eventually you could download data for real boxes from supporting manufacturers (we are not one of them btw) and see how they compare. You will certainly be able to evaluate the effect of line length at different frequencies over whatever venue shapes you desire.

 

Good Luck

[TonyMitchell]

Because then you can say to your client that you are using a line array. In a situation like the one you've described, that is pretty much the sole advantage.

 

I thought that were the case, i.e. where there's no coupling, going back to my example above, there's not even the benefit of any volume / headroom gain by deploying three times the MHF boxes you actually need.... this theory being backed up by the small ratio of subs to "line array" tops recommended by manufacturers, compared to point source, where loads of subs tends to be the order of the day.

[Stan Hope-Streeter]

Because then you can say to your client that you are using a line array. In a situation like the one you've described, that is pretty much the sole advantage.<br />

 

That is the correct, definitive answer.

 

"Line Array" is, in most cases, a Marketing concept, not an Engineering one.

[Shez]

You may find it interesting to perform some simulations of small arrays in the new (free) EASE Focus 2.

And here was me hoping to get some work done this afternoon... It's actually very instructive to experiment with different angles between boxes and different gains to try to get even coverage across a venue. I'd certainly recommend having a play with EASE - you'll very quickly see that a hang of four boxes is pretty pointless compared to a proper line source.