Array, or not to array? That is the question
Mar 14, 2012 2:49 PM, By Bob McCarthy
Speaker considerations for best deployment.
Let’s begin with a hypothetical question: Is a single loudspeaker better than an array of loudspeakers? If we can level the playing field by making the single speaker an exact match in power capability and coverage pattern, the decision is clearly in favor of the solo speaker. All other things being equal, we are far better off with a single source of sound instead of the complications and irregularities arising from multiple arrivals from a speaker array. Wouldn’t the ultimate speaker be a single device with enough power and coverage to fill a stadium? It doesn’t seem so.
Everywhere we turn, whether in stadiums or small theaters, we see more and more arrays of smaller speakers and fewer examples of large-format solo speakers. Are we chasing a fad or are there sound reasons behind these trend lines?
This two-part article will address the seemingly simple question: to array or not to array? The answer requires a few steps. First, we must establish the nature of the response of a single speaker. The behavior of an array is the sum of the parts, so we cannot possibly understand the grouped behavior of speakers without first knowing the individuals. As we learn about the single speaker we will find its natural limitations. Finally, we will see how the array behavior opens important new possibilities that a single speaker cannot practically achieve.
THE SINGLES PROFILE
Hi. I’m an 80-degree-by-40-degree active two-way speaker with a front-loaded 15in. woofer and 4in. diaphragm compression driver on a constant directivity horn. I have a working range from 50Hz to 18kHz and can make peak SPL’s in the 136dB range. I love Steely Dan and quiet walks on the beach. This is a typical solo speaker that might also find itself in small arrays. Exactly what is this character and what would it take to duplicate it with an array? First, let’s look at the peak SPL, a single number that integrates the maximum combined level over the entire frequency range. We can get 136dB SPL from two speakers that each produce 130dB, three that produce 127dB, or four that can generate 124dB each. Simple 20 log math. Next, we can look at duplicating the coverage pattern. We can match the 80-degree plane with two 40-degree elements, four 20-degree cells, or eight 10-degree units. We can even go nuts and do 80 1-degree elements.
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