yes, they have a bit of a cult following & there have been a myriad of slight variations gold, red etc., I own the 10 inch variation based on the SRM-B driver with both a stock Tannoy XO & the MANELY ML-10 variation. I also own Adire Audio HE10.1 (original & series II). A Colleague owns VLM Divas (floor stander with the Supertweeter phase array). The latter speakers use a variation of an Emmince driver (s)
If we were to contrast these 10" dual concentric based speakers with lets say a SSR or Garnet
most people like the "warmth" of the 10" dual concentrics, they often say dynamic, good off
axis sonics & sound-staging. They do well with a variety of Tube systems. They are not Highly
resolving in terms of "Hi-Fi" characterisitics.They are Easy to drive.
When I had some Ronin OB dual concentric/coaxial based SEAS speakers people again mentioned good off axis sound & dynmaics.
I have not heard your MF based coaxials but I have heard a highend design based on that driver with some lovley BE Maple cabinetry. Warm & nice offaxis sound. So with broad brush strokes I'd say there must be something to this design. Where the phase might be well maintained.
I am sure your client likes & enjoys these 15" drivers. I would assume he has a nice tube based system to drive these speakers. I have been looking for my Freq. Response measurements from GR research. But I have not been able to locate them on my HDD...perhaps they have been lost. Nonetheless, they were not ruler flat, however they were sorta smooth over a +/- 5 dB window.
At a few GTG most people liked these speakers & were quite frankly surprised that they like them as much as they did.