A Box is A Box. Not. Especially When it Comes to Speakers.

Posted by Bob Langlois on 2/10/15 5:20 PM

All speakers are not created equal.

A Box is not a BoxThere 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 for microphones. Sure we have learned to manipulate these designs much better, especially with the invention of digital audio processing. But all the basics are pretty much the same. The science doesn’t really change.

Even so, there is a huge misunderstanding in our industry, and especially in the House of Worship world in general, as to why certain speaker types exist. There is a very simple explanation for it. For those of us who care about the proper design, it is about getting direct energy where it belongs, in the most efficient manner possible, and 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. 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 in which 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 for a small room and not a lot of distance to throw. If done correctly, you get a little vertical control by using the physics of the horn pattern, believe it or not. Less is more in this case. Most of these speakers are good for around 40 to 60 feet with a few exceptions.

Horizontal arrays: 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. My favorite application would be as close to “0” degrees to the audience as possible, just above the listeners’ heads using the high frequency vertical pattern as a guide. If you have to put this array 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 manufacturers’ cabinets are definitely better than others when it comes to this type of design. All horizontal arrays are DEFINITELY NOT created equal!

Vertical arrays and line arrays: These are some of the most misunderstood designs today. NOTE: If you are not deigning in some sort of vertical pattern control for your client, you are probably doing him a disservice. All vertical arrays are not necessarily line arrays and vice versa. There are also hybrid vertical arrays as well. These are the vertically flown 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 and 400 feet and beyond. There are also 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. There are many sizes of these arrays, even down to arrays with 4” speakers that can be applied in smaller applications. One of my favorite 5” arrays I typically use for 75 to 125-foot throws. My favorite properties of good line arrays are not just exceptional energy shading at close and far fields, but also the comb filtering is vertical so when you walk laterally in a room it is not apparent. I can always get the last seat to sound just like the first. There is no reason to have to “kill” the person in the front row so the people in the last rows can hear. Vertical pattern control is crucial when it comes to controlling energy where it needs to go.

Subs: 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.

Rule #1 is to 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. My favorite is a single center cardioid sub array. This application lets me put energy in the seats while keeping it off the platform. There are many choices for controlling low frequency, and you just have to decide what the right method is for your particular application.

Steerable arrays, or beam steering: Some of the new technology is available and has actually been here for a little while. I did my first beam steering arrays in 2003. However, it is just now getting perfected with new digital technology and more robust drivers along with seriously better math. There are some true line arrays in single cabinets available now that can be steered vertically easily. This allows placement of 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 box arrays work, you will find 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.


 

A box is not a box, and fiber is most certianly not always just fiber.

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Topics: Audio