I discuss in this video: cross over, phase array, current limiting lamp and show you the inside of a Bose 802. The cross over is a low pass filter. Due to the difference in phase shift of one set of speakers vs the other, the speaker has a much broader wave front. This is not a Bose concept, but a concept of Karl Braun in 1905. It is just put to good use by Bose in their various speakers.
The Current Limiting Lamp is used in oscillator circuits to provide current stabilization. A lot of op-amp circuits use a neon lamp. In fact, there are quite a lot of "low-voltage (starved plate) vacuum tube compressors" that use a vacuum tube as a compressor. Basically, you can pull that vacuum tube out and put in a light bulb and accomplish the same "compression" characteristics. But, they use a vacuum tube because nobody wants a "light bulb" compressor.
Again, there is nothing new in speaker designs. Most all the concepts can be found in engineering texts from the early 1900's.
Original Work, Copyright 2015 James D. Whiteside, II all rights reserved, For consideration only, no reproduction without prior permission.