Hi I owned a pair several years ago. Please this is only my opinion and you know what the saying is about opinions. I was not happy but the designer is deceased so he is not here to defend his speaker(seemed a nice guy). The adjustment thing I spent hours tweaking. The threads for the adjustment screws just go into the concrete and once you move the screws in that concrete mixture they are gone(had to put in plastic inserts). The speaker cones are basically non removable as they thread from the inside another poor design. Then the 50.00 Pioneer woofers with stamped baskets he had me putting plumbers putty on them to dampen the ringing. And do not look at the 20.00 xover and cheap wiring plus the pieces of insulation had fallen down inside the cabinet I had to reglue them into place.. I know these sold for 10 grand but please mdf and concrete were not that expensive 10 years ago. Just my take and they sounded o.k. I just got fed up with them and their looks. Best wishes and I never mentioned this before now. You may love them. I am just stating my experience and not here to deride them as most other speakers are built just as cheap and cost just as much. Just watch some of the GR Research videos to see the truth.
Past or current Green Mountain C-3 owners
I own a pair of Green Mountain C-3 with the HX upgrade. I am currently driving them with a Coda N0.8 amp and a Lumin A1 directly using the Leedh volume control. I also have a pair of Seaton Submersive subs that I bring in under the C-3s that are running full range. I am quite happy with this system, but given the passing of Roy Johnson and the replacement tweeter becoming unobtanium I want to be thinking about where I might have to go next in the future. The C-3s just totally disappear in the room and I attribute a lot of that to Roy's design objectives of maximizing phase and time coherence as well as minimal diffraction enclosures for the tweeter and mids. I have other speakers I can rotate into this system in a pair of Martin Logan Summits and a pair of modded Klipsch Chorus IIs (fun speaker). Neither of these could replace the C-3s.
My question to past or current C-3 owners is what speaker have you moved to that gave you equal or better performance to what you got with the C-3s? Thanks for your insights