A Box is a Box is a... Really?
There is really nothing new in speaker design in our industry. Everything we know we’ve learned in the 1930’s and some again maybe in the 1950s and 60s. The same also holds with microphones. We have,
however, learned to manipulate these designs much better especially with the invention of digital audio processing. Still, all of the basics are pretty much the same. The science doesn’t really change. There are one or two exceptions to this, but they are an entire subject unto themselves and very much in their infancy in development and application. I will, however, mention them at the end of this list.
There is a huge misunderstanding in our industry and especially in the church world in general, as to why certain speaker types exist. There is a very simple explanation for it. For those of us who care equal about the proper design, it is about getting direct energy where it belongs in the most efficient manner as possible with the least amount of bad repercussions. Audio is all tradeoffs. In order to accomplish one objective sometimes we sacrifice another. Here are a few examples of basic speaker types.
POINT SOURCE SPEAKERS
This is basically a single speaker pointed with the business end to the audience usually on axis. Now these come in different sizes, shapes and dispersions. Some have very wide high frequency horns to cover a wide area and others are narrow for applications where you might have another point source speaker that you don’t want to interfere with. Maybe you have walls that you don’t want to reflect off of. This is a good solution where you have a small room and not a lot of distance to throw.
If done correctly you can get a little vertical control by using the physics of the horn pattern, believe it or not. Less is more in this case. Generally speaking, most of these speakers are good for around 40 to 60 feet throw distance, with a few exceptions.
In certain applications, the old standard “long throw/short throw” set up can be effective. This is where two loudspeakers are suspended one over the other, with a wider horizontal dispersion cabinet at the bottom, and a narrow horizontal dispersion cabinet on top, configured to provide coverage to the far seating at increased SPL levels. It can be a bit tricky to get this right during commissioning, but properly implemented can be a valid solution for certain rooms. There are superior solutions, but being an advocate of having many “wrenches” in my tool box, this solution should not be quickly dismissed.
Horizontal arrays are nothing more than a collection of point source boxes that are meant to play well together for getting energy in a wide horizontal plane. The best application would be as close to “0” degrees to the audience as possible just above the listener’s heads using the high frequency vertical pattern as a guide. If you have to put this array high in the air and point it down, you have probably just failed. The other drawback to having little vertical pattern control is horizontal comb filtering. Even the best horizontal arrays will have a certain degree of destruction as you walk laterally through the room. Some manufacturer’s cabinets are definitely better than others when it comes to this type of design. Basically, almost every manufacturer can build a great sounding loudspeaker that performs well alone. However, once arrayed and interacting with other cabinets, they can be quite destructive.
All horizontal arrays are definitely not created equal!
VERTICAL ARRAYS AND LINE ARRAYS
NOTE: If you are not designing some sort of vertical pattern control for your client you are probably doing them a disservice.
These are some of the most misunderstood designs today. All vertical arrays are not necessarily line arrays and vice versa. There are also hybrid vertical arrays as well. These are the vertically suspended multi speaker arrays you see in medium to large venues that are meant to cover, not only narrow and wide patterns horizontally, but are also meant to throw great distances. Sometimes this can be between 300- 400’ and beyond. There are some for stadium designs that go well beyond that.
There are of course certain laws of physics you must contend with such as high frequency loss at distance but, in general, line array technology is very useful for a lot of applications. Now there are many sizes of these arrays, even down to arrays with 4” speakers that can be applied in smaller applications as well. One of our favorite 5” arrays we will typically use for 75 – 125’ throws. One of the best properties of quality line arrays is not just exceptional energy shading at near and far fields, but the comb filtering is vertical so when you walk laterally in a room, it is not apparent. We can always get the last seat to sound just like the first. There is no reason to have to rattle the fillings from the teeth of the person in the front row so that the people in the last rows can hear. Vertical pattern control is crucial when it comes to controlling energy and directing it where it needs to go.
PHOTO ABOVE: CENTER CARDIOID ARRAY: NOTE THE EVEN COVERAGE AND LACK OF ENERGY ON THE PLATFORM.
Mono subs, Stereo subs, Cardioid subs, End-Fire subs. What is your application? Wow, so many options.
Controlling low frequencies is a fairly easy thing to do. Why a lot of designers don’t do it is a mystery to me.
Ok, rule number one is use the least amount of sub sources as possible. More than one low frequency source can add destruction in places where you don’t want it. Steer frequencies where you want them and use frequency cancellation where you don’t. This is done in a few different ways. One of the most effective is a single center cardioid sub array. This application provides the ability to direct energy toward the seating area while keeping it off the platform. The images below indicate the predicted coverage of a center cardioid array and a traditional split sub system, where the subs are placed directly beneath the left/right main arrays.
There are many choices for controlling low frequency, and a good system designer can determine what the right method is for a particular application.
STEERABLE ARRAYS, OR BEAM
Ok, some of the newer technology that is available has actually been here for a little while. We implemented our first beam steering arrays in the early 2000s. However, the technology is just now getting perfected with new digital processing and more robust drivers, along with seriously improved math. We can now perform beam steering that is phase linear, something that was sacrificed in the early days of beam steering. There are some true line arrays in single cabinets available now that can be steered vertically exceptionally well. This allows placement options in odd locations where it is not convenient to place a traditional speaker. There is even a way to control the vertical splay for direction and distance. Once you get a handle on how these column line arrays work, you will discover applications for them you never thought possible.
Understanding that there is a science and math that goes into your speaker choice for your specific application is the best place to start. Understanding how you are using that application is also a critical factor. Don’t let your eyes glaze over when it comes to choices. There are people who spend countless hours in research to determine the best sciencefor the best results for specific types of loudspeakers. They are extremely knowledgeable, and it’s a great asset to allow them to do what they do. Our job is to apply that science and technology to specific rooms.
Acknowledge that not every type of loudspeaker is the right choice for every application. I meet with many churches who, from the first moment we begin discussion of their audio system, inform me that they insist on line arrays for the new system. Well, that’s great, if line arrays are what the room calls for. Sometimes it’s the perfect solution, and other times, not so much. Understanding the differences is crucial to making wise decisions in loudspeaker selection.
Daryl Porter is the Vice-President at Second Opinion Audio, LLC (SOA)
PHOTO ABOVE: SPLIT ARRAY: NOTE THE AREAS WHERE THERE ARE GAPS IN COVERAGE AND THE “POWER ALLEY” DOWN THE CENTER SECTION OF SEATING. ALSO, THE PLATFORM IS BEING EXCITED WITH LOW FREQUENCY ENERGY.