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- Apr 20, 2020
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I think you are nitpicking here in order to try to argue that somehow this is not novel and was done before. Again, the way the expanding array works is not the same. I am not sure what part of that you are not seeing. In the expanding array, there is a traditional crossover between the midrange and tweeter. Overlap is typical of the order used. They are symmetric. It is a true crossover. In the Perlisten, the tweeter in the center along with the midrange drivers all have a highpass filter at 1khz so they overlap substantially. There is a point where the midrange is phased out so that eventually the tweeter is the only driver operating. But there is large overlap between those points. Something like 4-5 octaves.Hard crossover? Is that a technical term? David Smith put a lot of effort into determining how to place the speakers geometrically, and what order crossovers to use in order to create the dispersion pattern he was after. The results is a consistent Maximum Response Axis across the band of interest, with attenuated response at angles away from the MRA. That's a beam. He achieves this largely by using an array of multiple transmitters (aka beamforming). Compare the dispersion he achieves with his expanding arrays to a pair of full range drivers stacked vertically, and you'll see how important all the driver interactions are.
I have never heard beam forming defined like you are. All speakers have a forward radiation lobe that is directional. MTM and WMTMW designs have created symmetric lobes and also have existed for a long time. But I never considered those beam forming designs. If you want to, that is fine. I think we are just mincing words.
the Snell and Perlisten approach are not similar or related. That remains true. Call them what you want.