Omnidirectional vs Omnidirectional Point Source

99%  of all loudspeaker systems are mono-pole designs. That's the common or garden variety standard woofer/tweeter arrangement fitted to the front of a box. The remaining categories consist of :  Di-pole - these include open baffle types in which the signal coming from the front of the speaker is out of phase with the rear. Bi-pole - these include front and rear mounted drivers which radiate in phase and result in a figure eight dispersion pattern. Direct/reflect type - these send part of the signal towards the listener and part of the signal to bounce off room surfaces to create a more spacious effect. The final designs are Omnidirectional - these designs launch the signal in theory into a 360 degree angle at best and always with limited vertical dispersion. There have been many attempts over the years to design a speaker with a wider dispersion pattern but the marketing departments seem to get over zealous with speakers firing six ways from Sunday. There were a few examples which had a four sided box with drive units on each face. They offered "the open and spacious sound of the concert hall..."  except all you got was four times the diffraction and lobing problems and a total soup of confusion due to all those sound sources. There were several versions of a bog standard woofer firing forward in a cabinet with a tweeter parked on top to give a more "open" sound. This simply resulted in a speaker which, due to the dissimilarities of dispersion pattern from lows to highs sounded  incoherent from top to bottom. A not uncommon problem with just about every speaker system.

The "pulsating sphere" approach has been the holy grail for decades. It presents a few obstacles. One being that it's a physical impossibility. Never mind, Mother Nature can be cruel. Fortunately, our ears will accept a "pulsating half sphere" as being a point source. This is still a miserable engineering challenge but it has been achieved with the Morrison Model 19.1. 

Don Morrison

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