I recently read that one is unlikely to see a flat panel speaker used for public address in a gymnasium or auditorium. The assumption was that because the above is generally true, one would/could/should not use a flat panel speaker in a classroom audio distribution system either. Hmm… The astute observer will note that you don’t see cone speakers in gyms or auditoriums either. You will usually see horn speakers because of their efficiency and sensitivity. Cone speakers, like you have in your sound system at home, work best… in your sound system at home (and in your car). You typically have several of these speakers as part of your stereo or home theater, and they are spread out in such a way as to provide good sound for music and movies.
It turns out that a flat panel, forced resonance speaker is perfect for classroom audio. Why? We’ll get into the physics of it in a later post, but because the signal we want to distribute in the classroom is usually a speech signal, the frequency response, dynamic range, and dispersion characteristics of flat panels is ideal. They produce the audibility and intelligibility cues of speech at a comfortable level and maintain excellent performance off axis. This means that students receive improved access to direct instruction no matter where they are in the room, even when only one speaker is used.
Here is an example to illustrate my point. Below are two spectrum analysis plots I recorded at a conference where a single flat panel speaker was being used for audio distribution. At a glance, can you tell which measurement was obtained directly in front of the flat panel speaker vs at a location almost 90 degrees off axis? There isn’t much difference, is there? Preserving the high frequency, intelligibility cues for listeners that are off axis from the speaker is key, and is something that flat panel, forced resonance transducers do very well.
I’ll talk about the physics of flat panels and the concept of forced resonance next time (it’s cooler than it sounds – no pun intended).