Click to download PDF – Concert System Comparison
The Synergy Horn Difference-
People have often been skeptical when they hear how few Synergy horns it takes to do the large venues like stadiums that we have done, especially if they are accustomed to using line arrays. What follows will put this large difference in perspective using the same approach auto makers often take when they compare the data between different models of cars.
This is done by comparing things like horse power, gas mileage, time from 0 to 60 mph, weight and so on. In this case we are using the data taken directly from each manufacturer using their computer aiming software and predictions. You are encouraged to check to confirm with your own predictions. Unfortunately one cannot hear the sound quality aspect of this, but frequency response and loudness can be seen visually.
This comparison is also done for a large sound system using 20 boxes and hung 30 to 50 feet off the ground a reasonable distance for such a large array, compared to one J-3 cabinet at 30 foot. The SPL / frequency response curves are shown at maximum level and have been gathered with microphones in the prediction software placed at various distances (the same distances for all the speakers).
As one can see the systems all reach a considerable SPL; although, the J-3 is the loudest and most consistent over the audience distances. The natural question is: how can just one box produce so much sound and be more consistent over the same distances? The answer is that while it may also be a “black box”, the J-3 works on entirely different acoustic principals which liberates it from several down sides of the line array and also has several advantages over the line array. First, it is a full range constant directivity horn, so when flown and aimed at “the back row of seats” it can deliver a more constant SPL vs distance than the line array.
As one moves closer to the source, you are moving progressively out of the horns pattern, with constant directivity, that means that the SPL falls but the frequency response stays essentially the same, unlike the arrays. The result is that, up close or far away, the spectral balance and SPL is much more constant.
Acoustically, line arrays have sources that are usually too far apart to add coherently and so depend on Huygens wave front synthesis which means there is both constructive and destructive interference. This means that a considerable amount of acoustic energy is lost in destructive interference (self-canceling other sources) which requires many more drivers to do a given job. The interference patterns are also why the line arrays have a “limited usable throw” while the synergy horns have been used out to several thousand feet and still sound very good. The line arrays produce an interference pattern which means a great deal of energy is projected above, below, and to the sides of the desired direction. This results in sound radiation in directions other than where the people are, and is very bad for voice intelligibility when used indoors. Interestingly enough, some line array modeling software shows this extra radiation, while others do not.
This same spatial interference pattern moving around can be described as a swishy sound when there is just a little crosswind in a stadium or outdoors. Line arrays are also a combination of direct radiators and have minimum horn loading using very small horns which means low efficiency.
In the Synergy Horn design, all the drivers are less than ¼ wavelength apart where they combine and interact, because of this they combine coherently into one new source without destructive interference. The result is constructive addition and no interference patterns; all the energy is coherent as if it had been a single driver. All the drivers are horn loaded into a large horn so there is both a much higher efficiency, and with greater directivity, there is less energy going up, down and to the sides, making it louder in front and quieter in the back and sides.
While the modeling software assumes a steady state condition, much of music and all voice information have transients which is a big reason why the Synergy horns “sound different” (subjectively better) and have higher measured intelligibility. In this case, a single impulsive signal (e.g. a finger snap) fed into a synergy horn results in a single impulsive event arriving at ones ears while the array delivers multiple arrivals in a sequence that changes depending on how far away one is from the array. A single impulse makes musical instruments that are struck (drums-percussion) or picked, sound natural. When those signals are smeared with multiple arrivals, the sound can become dull and lifeless.