AF’s Weblog

February 3, 2010

Zoned, Summed & Line: Array Structures & Performance

Line Array-Type Systems’ Industry Dominance in Live Sound

arrays

This feature article is provided by ProSoundWeb

I’m asked a lot of questions about sound.

Many of them focus on unraveling and understanding some particular function, feature or concept, while others are directed toward distilling my opinion on methods or industry trends.  A while ago. I was asked some questions that led me to some in-depth pondering.  The questions: Why are line arrays so popular? Are they a fad or here to stay? And what will be the “next big thing”?

The fact is that line array-type systems have taken the professional sound reinforcement industry by storm. Nearly every manufacturer offers several choices.  But just what is it about line arrays that have positioned them to completely dominate the industry? Is it just a gimmick or is there truly some aspect of the vertical configuration that offers an inherent advantage over other system types?

Stepping back and taking good long look, I found that there are several properties these thinner line systems possess that are readily apparent, plus one substantial advantage in particular that is not so obvious at first but perhaps most important of all.  Just to keep things interesting, and hopefully clear, I’m going to examine the basics of sound system design from a slightly different angle than perhaps is common.

In The Zone

arrayacdc
Electro-Voice X-Array on the big AC/DC world tour last year.

A conventional and intuitively logical approach is to deal with a large acoustic space as a set of smaller zones. To cover the area, one constructs clusters of loudspeakers, each aimed at a particular region or zone. Each loudspeaker box in the cluster can then be optimized in terms of EQ and volume.  With this approach – which I will call “zonal coverage” – it’s advantageous to minimize the overlap between the box-to-box coverage patterns. The goal and challenge for the system designers and technicians setting up the system is to try to achieve smooth sonic transitions from zone to zone.

This system is constructed such that listeners are not exposed to sound emanating from boxes that are in close physical proximity to each other and at different distances. More simply put, sound from multiple sources arriving at the ear at differing times equals “not so good.”  When projecting sound over varying distances, some issues arise. The coverage area of each box increases in size with distance, meaning the angles between boxes pointed far away should be increased.  Yet volume naturally drops with distance, so to maintain volume at distance, the inclination is to decrease the angles between boxes in order to have more of them pointing at the far-away zone.

As a result, zonal coverage systems often employ longer throw, narrow dispersion loudspeakers to help solve the dilemma.  Electro-Voice X-Array, Nexo Alpha, and Turbosound Flashlight and Aspect loudspeaker systems are all excellent examples of zonal systems.  Much effort was put into these loudspeaker designs, in order to achieve distinct and consistent vertical and horizontal coverage projected from each individual box.  Usually, they employ relatively few drivers in each box, with horn-loading assisting with pattern control.

Now let’s take a closer look at some other systems…

Making Arrangements

So here’s the deal, at least as I see it.  With current technology, it’s necessary to utilize multiple loudspeakers to cover large spaces, as no one makes a single loudspeaker that is loud enough, sounds great, and versatile enough to handle a wide range of venues/coverage areas.  These multiple loudspeakers need to be arranged in some sort of configuration that is horizontal, vertical, both, or even one behind the other.

Currently, we can get loudspeakers to sum together quite well – but not perfectly. We can also get them to zone together quite well – but not perfectly.  Our ears are very sensitive to those imperfections in the horizontal domain and considerably less sensitive to those same imperfections in the vertical domain.

Therefore, the true design advantage that line arrays posses is that they take advantage of the human deficiencies in vertical hearing by keeping their imperfections in the plane where we less likely to perceive them, presenting a low degree of component-to-component imperfections.

Combine this with the fact that they hang nicely, like a string of beads, and I venture to say that line arrays may just be a bit more than the latest fad.  As far as the question – “what’s the next big thing?” – well now, that is the million-dollar question, isn’t it?  My bet is that it will be a technology that better adapts the way music is presented with the way we hear it. Or, of course, it might just be something cheaper, smaller and more convenient with a sonic downside, like the MP3 format.

To read the full detailed article please see: Array Structures

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