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
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.
Electro-Voice X-Array on the big AC/DC world tour last year. (click to enlarge)
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.
I tracked my rhythm guitar in mono but I think it needs to found more full. What can I do?
In reality the summing in line arrays is not nearly as good as we are led to believe. The vertical arrangement perhaps allows us to kid ourselves that combing and interference is not too bad, but actually this is not so.
For instance in the case of many line arrays, inefficient direct radiating 8 inch (or thereabouts) loudspeakers are used for mid-range frequencies up to around 2kHz. This means that the distance between the centres of the drivers are typically at an average spacing of around 9 inches, allowing for cabinetry and rigging. Any frequency whose half wavelength is less than 9 inches will act as an independent non-coupled source. So, all the important vocal mid frequencies between 750Hz and 2kHz will be subject to combing which is evidenced by the extreme ‘phasiness’ of line arrays in the slightest of winds. This is very ironic as in the early days of line array they were held to be superior to point source because they were less prone to phasing when one walked across them. Now, when there is wind, you can enjoy the same effect without even moving!
In the High Frequency region a similar thing is taking place. HF elements with inadequately controlled vertical dispersion driven by the ubiquitous and terrible sounding compression drivers are arrayed at tiny increments of a degree. Many systems don’t even have cone mid speakers and the compression drivers have to struggle with midrange duties as well. Because of the relatively low efficiency that comes with wide dispersion and the tendency of these devices to produce huge amounts of distortion when driven hard, large numbers of them are needed. These stacked arrays of compression driven wide dispersion horns (often there will be 12 or 16 units pointing in the same direction) bring with them yet more problems. Combining (or summing) rather better at the lower end of their range and interfering and comb filtering terribly at the upper end these arrays exhibit severe roll-off at high frequencies. Add to this the fact that these drivers are always too hot at 2 -3Khz when driven at any kind of level it follows that extreme amounts of EQ are needed to address this and there goes the phase response and the headroom.
Even in still conditions, the arrival time difference between one line array box and the next is in the order of 60 micro-seconds, which is at least three times greater than the lower limit of the human auditory system’s time resolution. This gives a smeared transient due to multiple arrivals which is perceived as a remote event. This is why line arrays always sound ‘over there in the box’ and do not give an involving perception of dimension and space. We at Funktion One have steadfastly refused to engage with this mass pandering to fashion rather than attention to audio quality. Audio’s true potential will never be realised with line arrays.