Is anyone thinking about building Walsh drivers?

Glo,

Sounds like a rational plan.

I suspect many who are fond of the older generation (near) full range Walsh drivers and wide range DDDs in particular tend to be enamored more so with the Walsh driver top end sound.

The newer OHM CLS drivers take the opposite approach, using a conventional tweeter/super-tweeter crossed over to the Walsh driver at as high afrequency as possible, at ~ 7-8 Khz AS I recall.

I gotta say though that I find it hard to understand how anyone could not be impressed with the overall smoothness and detail including the top end that at least the newer OHM CLSs are capable of delivering. I say capable in that I find the limits so far depends on what's upstream more so than the speaker itself. I have heard major differences from absolute top notch to just so/so depending on the specifics of whats upstream feeding my OHM series 3 CLS speakers. The ARC tube amp with teh newer and pricey West German 12AX7 tubes ARC now is providing, the carefully matched BEl Canto Class D amps, and either somewhat humble phono or digital sources I use currently are in that top notch class IMH and also maybe somewhat biased opinion.

If you do it successfully for modest cost, maybe approach John Strohbeen to see if the Walsh tweeter might be utilized in the 2-driver CLS configuration maybe? That might be interesting!

Mapman-
I'm surprised The new Ohm management hasn't jumped on this myself. Infinity crossed at 10KHz, much higher than the "new" Ohm's 8 KHz.. Ohm did license the tweeter to Infinity, but it was probably done during the old regime. Maybe they forgot. The Infinity seems to have gotten a measure of critical acclaim.
The high crossover point fits Ohm's current model, and the offers the advantage of being co-incident to the primary driver's axis. The Infinity had 4 crossover points, three of them in the critical presence band, and moreover it's location on top of a larger rectangular surface without a doubt caused numerous diffraction problems.
I have listened to both the old "A" and "F" models set up properly, and personally, I think that "stuffing a pillow" behind the driver as Ohm is presently doing is not the way to go.
As far as electronics go, you are preaching to the choir.

"I think that "stuffing a pillow" behind the driver as Ohm is presently doing is not the way to go."

I think this is the standard configuration provided to enable speakers to go closer to rear wall than full omnis otherwise and allow the speaks to fit into more peoples rooms like other speakers more easily.

That may be why they pass on the omni/walsh style tweeter. I'd like to see it though if possible in order for the dispersion characteristics to be similar top to bottom regardless of whether full omni or not.

I imagine cost management is a factor in the decision making process as well. The tweeter they use sounds very good. A "custom" Walsh style tweeter would likely add cost. Maybe a premium model of some sort with a separate Walsh tweeter might fly and still come in for a lot less than GErman Physiks, mbl, and their ilk.

But I also suspect that the niche high end market is not something OHM is really all that interested in, at least in the US, although they have started to market overseas in GErmany and elsewhere I suppose where their products can compete with the mbls of the world in a larger market for much less I guess.

OHM does do full omni versions for surround sound systems normally I believe where the sound absorbing materials inside the can are omitted.

I can see your point concerning close wall spacing. The omni's need a lot of room to breathe, and creating the correct acoustical environment is black magic a lot of folks would just as soon avoid.
As for the tweeters, they take a lot of skilled labor to build. It's not something you can pop out of an injection mold, and the key to profits these days seems to be not paying craftsmen or worse, farming it out to the Pacific Rim.
One of the ESL companies, I believe it is Acoustat, moved their production from the UK to China to contain costs. The Chinese company immediately started selling a knock-off with a different name for about 1/3 the UK price. The Chinese seem to be very challenged when it come to intellectual property

Mapman... You can mount a conventional cone driver backwards firing down, but it isn't at all like a Walsh driver.

The angle of the cone and its material must be such that sound propogated down the cone material is delayed by a time that, at every point down the cone, matches the delay resulting from the angle of the cone. (Sorry I can't explain that better). This is the key design feature which enables its superb phase coherency, as evidenced by accurate reproduction of a square wave.