bcschmerker4
That's bcschmerker4® to you!
In pro audio, Eminence Speakers manufactures a sub-line of the Beta musical-instrument speaker range that can take compression drivers with a 1-3/8-18 threaded snout, firing them coaxially through the Beta voice coil. Some other speaker manufacturers use the same principle in competing musical-instrument applications; TANNOY® does the same thing for near-field monitors. I reckon that this principle can be scaled down to coaxial in-ear speakers, using any of a specific subset of the Knowles® balanced-armature line-up, or alternately a piezoelectric dome speaker, as the tweeter to fire coaxially through the voice coil of a dynamic woofer driver. What earphone and earset manufacturers have products with coaxial transducers; and how difficult are they to balance as two-ways?