After a little AES business and group introductions, Mark Rogers started with a revue of the concerns when arraying loudspeakers. One wants to cover the audience - not walls, ceilings, mikes, etc. if possible. One also doesn't want destructive interference between speaker boxes.

Referring to the classic Don & Carolyn Davis text, Sound System Engineering, the ideal point source would have coverage angles exactly on the audience and the directivity, Q, would vary to every seat in house to give perfect sound to every seat. Since this is impossible, you usually need arrays, which are still a lot of art as well as science. One must must bend the "rules" to make a practical system.

Again referring to Davis, the best choices for a reinforcement source would be, in order:

1. a single speaker
2. a central cluster (often erroneously called a point source)
3. an overhead line array
4. overhead distributed speakers with high density & overlapping coverage
5. global speakers, such as many speakers on the backs of church pews
6. headphones!

Mark reviewed why arrays are a necessary evil. Remember that in many boxes, HF & LF drivers are really an array; if you can't cover audience with one speaker, you must array; and for sheer power, such as concert reinforcement, you need multiple speakers and you must array them in some way.

The problem with arrays is that spatial separation equals separation in time at a given angle. This can lead to combing (ragged frequency and phase response), lobing (ragged directivity patterns), and echo. One needs to minimize these effects, although you cannot eliminate them completely. Time delay to drivers also affects these problems, and effects differ with frequency, due to varying wavelengths of the audio.

Among the worst cases is when the path lengths are off only a little - you get large wave cancellations and very ragged direct field frequency response. You don't see how bad this is on an RTA (real-time analyzer), as reflections "fill in" the response curve. So, split sources - avoid them, especially on speech systems.

Mark went on to show several plots, such as an older multicell horn response at 90 degrees and on axis with ragged response. Horizontal or vertical arraying still has the problem. He showed more complex arrays (from a JBL book) and response curves with added horns. Then a (TEF) plot of the direct sound of a split pair at 30 degrees.

How do you align the array? Set the horn mouths for best coupling? Or align the diaphrams? Mark aligns the mouths, then uses time delays to align diaphrams to the "sphere source" model. He also showed an example of an older 3-way JBL box with array problems, and old steel "Manta-Ray" horns system, aligned.

Next, Dan continued with demos incorporating the Meyer SIM 3 analyzer. Several speakers systems were demonstrated, alone, and then in one or more array configurations. The analyzer allowed showing the response curves in real-time of the electronics and the acoustic output. A lazy-susan rig allowed rotating the rigs so the audience could hear the lobing and interference effects without moving from their seats.

The first system tried was an older Meyer box, the UPA-1A. First one box was played, then two boxes with several different splay angles.

After an intermission, door prizes were drawn. Winners were:

• Meyer shoulder bag - Ken Lorenzen
• Cool lanyard, Cool Sharpie - Janey Wallick
• Meyer cap - George Gilman
• Meyer Polo Shirt - James Avila
• Ben Harper CD - Ivan Tashev
• Johnny Cash CD - Rick Smargiassi
• Sheryl Crow's Choice CD - Chance Unterseher
• Shure T-shirt - Jasha Droppo
• India.Arie CD - Phil Nickolay
• Shure T-shirt - Meghan Claire Moyers

Continuing with the demos, several convex array configurations were tried, then several flat front arrays.

In spite of recommendations for single sources for maximum clarity, Dan allowed to a preference for spaced arrays for music concert reinforcement. To him, they sound more musical and/or spacious than a single cluster. A question was posed to Dan: would he go to a center speaker if he had a room with acoustic problems? He said he has used one stack, but seldom does. One key is to figure out where a room bounces energy back and to not aim speakers there. Mark Rogers also said you could turn one stack down maybe 6dB and it would be quite effective.

At one point, JJ Johnston asked the audience to plug one ear during a rotating pink noise test to notice the difference in spatial recognition versus using two ears.

An unusual array using Meyer UM-1A monitor speakers laying on their sides and splayed horizontally was demonstrated. Surprise was expressed that it sounded as good as it did, and Dan used it as an example of how good workable arrays are not necessarily the most obvious ones, or made out of the most obvious components. A conical horn monitor speaker array was demonstrated.

Also arrayed and demonstrated were boxes from Meyer, Genelec, and Mackie.

It was noted that the shape of the box (such as trapezoidal) was not necessarily related to how to best array it. Also, it was pointed out that there were no demos of 3 or more box arrays.

Dan also spoke a bit about the Meyer SIM capabilities and expressed hope for a local users group. A crashed laptop preempted attempts to show some final photos of real concert arrays.