After reading through these messages I feel compelled to dispel much of the misinformation contained herein, excepting Chris who actually worked on the design prototypes and as such is authoritative.
1. The Walsh micros, and the full range Walsh 5 and it's smaller breathren, utilize the Walsh bending wave principle wherein cone breakup is controlled through wave termination at the surround. Thus, the apex of the cone produces the highest frequencies - the sound heard is in fact coming from the front of the cone (the "back" of the woofer as it were). The high frequency extension is naturally limited by the mass and inductance of the voice coil.
2. The great advantage of the Walsh mechanism is that the full range from the lowest bass to the upper midrange frequencies and treble (to circa 8 khz) are produced by a single driver without a phase-shifting crossover. The omni-dispersion of the Walsh driver provides for perfect overlap of frequency response and power response (total radiated acoustic energy on and off axis) and seamless crossover to the tweeter, which is substantially omnidirectional (at the crossover frequency) due to it's small radiating area.
3. As bending waves travel down the cone faster than the speed of sound in air (supersonic wave transmission line), and as the cone is angled so that the total distance of wave propogation traversal is a multiple of the driver horizontal radius, it is possible to produce a perfect wave from from low bass to the upper cutoff frequency (i.e. 8 khz): there is no phase shift or time delay. The Walsh driver can pass a square wave. Conventional loudspeakers cannot produce a square wave except perhaps at one specific point in space.
4. The Walsh driver as implemented by Ohm has been modified to attenuate the rear radiation field and result in a high dispersion frontal radiator - the modern Ohms are not "omnis" as the Ohm F was. This design choice makes for easier room placement, minimizes room interactions, results in a warmer tonal balance, and improves the stereo image specificity, without sacrificing the spaciousness of the sound field produced.
4. The Ohm Walsh design provides for controlled directivity, vis-a-via the upper operating range of of the main full-range Walsh driver, and the tweeter. The tweeter is baffled in such a way as to provide for smoothly increasing directivity. The tweeter is directional above 10khz by design because in the highest octane reside the directional cues which provide for localization (imaging). There is no great advantage to an omdirectional radiation above 10 khz - in fact, it generally results in an over-bright fatiguing sound with compromised imaging and requiring acoustic damping of the room walls to counteract it by eliminating early reflections.
5. The perforated can is acoustically transparent - it's only function is to physically cover and protect the driver construct. It is not a diffuser.
The advantage of producing a coherent wave from low bass all the way up to far above the region of maximal human auditory acuity (circa 2-5 khz) is the resulting sound quality: natural, clear, detailed without the phase-shift, lobing and power-frequency response mismatching that plagues all conventional multidriver loudspeakers and rob the music of natural detail resolution, add coloration, and render a contrived quality to the sound. Also, the Walsh driver affords a very large radiating area for the production of the critical midrange, and it's geometry provides for perfect dispersion in the horizontal plane. The former characteristic results in extremely low distortion as excession cone motion is eliminated - the latter eliminates the beaming and cone-breakup that palgue all front-firing woofer cones, even exotic materials. The Walsh driver can hence be run full-range up to it's bandwidth limit, this eliminating the need for a signal mangling crossover with its energy-storing capacitors and inductors.
To really grasp the design advantages of the Walsh driver listed above, one need only listen to an Ohm Walsh loudspeaker in a proper setup to appreciate it's superior depiction of acoustic space and musical performance vis-a-vis conventional loudspeakers.
