History on ohm A's and F's.

The operating principle of the DDD driver, as used in the German Physiks HRS 120 (10-inch acoustic suspension woofer below 240Hz):

"The lower frequency end of its operating range can be described with Thiele/Small resonant parameters, while in the next frequency band up to the coincidence frequency 'it works like a pistonic driver'. Next, there’s an overlapping band where pistonic movement is 'progressively replaced by bending waves until all the radiation is generated purely by bending movement in the cone'."

Hi-Fi World review here.

Csommovigo,

Sounds like a reasonable accounting of the similarities and differences to me. Thanks.

IS it accurate to say that the different designs all operate on similar principles despite the fact that the implementation of each is significantly different, for better or for worse?

One other question I had was is it accurate to say that the lower frequencies with all of these designs are produced "pistonically" while the upper frequencies are produced by bending waves?

If so, then the Ohms must rely less on wave bending because the upper frequencies (>~14000 khz, I think) are produced by the separate tweeter whereas for most of the GP speakers, the low end (pistonic range) appears to be handled separately .

Still, other than the on e GP model I think, the Ohm Fs and As are the only speaks that use a single driver for the full range.

An advantage of wide or full range is the elimination for the need of a separate crossover device and a more "coherent" sound overall.

To my mind, it's "hardly a reasonable accounting of the similarities". In one case, we have an actual working model of a concept just a few decades old, as opposed to some drawings done centuries ago without any known working models. The Walsh "concept" may not have been as polished as the DDD due to the fact that Walsh died before he had the benefit of computer modeling to do the intricate math. Never the less, let us not forget that the working Walsh design had an even even greater frequency range. As Walsh had little to do with Ohms production standards, let us not blame him for alleged failure rates. Let us give the credit due to Walsh, without whom "Dick" might never had the premise upon which to refine and develop the the concept into the DDD. I'm just an outsider here, and while sincerely appreciate the input of those directly involved with these most interesting speakers, I'm a bit put off by what appears to be a slanted, unconfirmed and disrespectful assessment of the genius(?) of Walsh, and this applies to others who haven't posted here as well.

"Curiously - to say that the DDD is a variation of a Walsh driver (as described in LW's patent), in a fashion, to say that the Blackhawk helicopter is a variation of a drawing of a flying machine by DaVinci. While the DaVinci is certainly elegant and inspired, the GP actually works, and works with predictable precision and reliability."

This part is a bit biased I suppose.

Has GP's DDD driver solved the robustness issues of the original FULL range Walsh drivers on the A and F?

It doesn't seem so to me since it is not full range and does not deliver the low end. Unless I'm missing something, the DDD solution appears to be to avoid the problem, ie separate the low end off to another driver to avoid the stress and wear issues associated with delivering the low end "pistonically" along with the upper range that is delivered via wave bending all with the same driver, as I believe was done with Ohm As and Fs.

For newer Ohm Walsh speakers, they've elected to deliver the low end via the wide range (still not full range) Walsh-style driver. The rational Ohm provides is that most of what most people can actually hear (up to 14000khz or so) is delivered via the single driver and that preserves a lot of the benefits of the original Walsh driver design while avoiding the inherent fragile nature apparently of the full range Walsh driver design.