Why do only US makers focus on time coherency?

No, there is no such thing as a "best speaker design", but not all speakers are created equally. I think speaker design/theory/approach/methodology/materials etc. is extremely important, otherwise designers wouldn't spend the extraordinary number of hours and cost to research and develop different approaches. The sound of these design theories will vary greatly in different situations and with associated upstream equipment and even with varying types of music.

If one is going to make a sizeable investment in a speaker, then it behooves the individual to do their homework. Buyers remorse is not an experience I'm interested in becoming intimate with.

Bombaywalla ... I heard the DM603s and the imaging was far below that of the Spicas, though they had much better dynamics. When I heard reviewers say that ls3/5s image well I wonder if the same reviewers ever heard tc-50s or angelus, because the ls3/5s are not in the same league.

Bomarc ... agree the proof is in the listening. That said I'm just musing as to why the spicas do the spatial thing so much better than all other comparably priced speakers. Since all spica speakers have this attribute it's not coincidence ... some aspect of Jon Bau's design directly created it, and I suspect it is attention to the time domain response.

Dawgbyte: Thanks for the info on that thread. I'll check it out when i get done posting here.

The Ohm F Walsh designs were phase and time coherent, but they can achieve this coherency only at one specific listening height. This height will vary with the distance that one is located from the drivers. The non-linear pitch of the cone for the Ohm A and the use of another radiating source in the Ohm G negate their potential to achieve time & phase coherency. Other than that, the current offerings by Ohm are neither "true Walsh's" or phase & time coherent. While i know that Dawgbyte is not alone in this, people should not lump all Ohm's that refer to using "Walsh technology" or "Walsh driver's" as being one & the same. As far as that goes, the newer Ohm's are NOT EVEN CLOSE to offering 360% of radiation at any given frequency. If you listen to them and like them, that's fine. Just don't buy the marketing hype about "Walsh technology", etc... Sean
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Dawgbyte: From what i saw of Mitch's crossover design from his speakers, Hales are not time / phase coherent. There was an 18 dB / octave crossover in there somewhere if i remember correctly. Sean
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Thanks Sean, I thought the Hales were almost identical in design to Theil's speakers. I stand corrected.