Compression Driver with diaphragm at back of magnet vs at front

Geometry.

Since diaphragm dome is a section of a sphere, and sound from all of its surface must converge at the same time at the horn throat; diaphragm-at-front is clumsy imperfect while diaphragm at back is natural, so better and simpler.

All radial paths are same length if diaphragm on back, while on front only a clumsy approximation is possible, so first is used in PRO drivers, latter only in cheap cheesy "PA horns" or cheap horn tweeters.

Good:

CompressionDriverFigure1.jpg



The-phase-plug-is-made-of-several-parts-making-up-the-throat-and-the-slits.png


Wonder why Altec call this "Tangerine" 😉
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Cheesy-cheap street PA horn driver, notice bulge of driver and (poor) phase plug at front:
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Cheap horn tweeter (Fostex) cast zinc or plastic front phase plug.
Those holes are only an approximation of what´s actually needed.
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