One more observation:
JGH was particularly bothered by and critical of a particular type of coloration, one very common amongst loudspeakers. He even came up with a term for it: "Vowel coloration." He defined and explained the term in one early-70’s Stereophile speaker review I read, and I immediately understood of what he was speaking.
LIstening as much as I do to music containing harmony singing, my first test of a loudspeaker is in its’ ability to reproduce voices "accurately". Hearing voices as much as we do, it’s easy to hear when a speaker is adding coloration to singing voices; most do, to one degree or another. When I hear vowel coloration being added to voices, the speaker doing so is immediately crossed off my list of acceptable choices. I have established a very high bar in that regard.
In 1973-4 I made recordings of my wife and young son speaking, using a nice condenser microphone JGH had reviewed in Stereophile plugged straight into a Revox A77. I also recorded (with a pair of the mics) the Jump Blues/Swing band I was then playing in, both in a rehearsal space and live in a local bar. Upright piano, electric bass and guitar, tenor and baritone saxes, my Gretsch drumset and Paiste 602 cymbals, and male vocals.
Both recordings serve as excellent references when evaluating loudspeakers, better than almost all commercial recordings, most of which have been subjected---to one degree or another---to all kinds of electronic manipulation, rendering the "accuracy" of the recorded sound unknowable. What should they sound like? Who knows?!
One notable exception are the direct-to-disc LP’s on the Sheffield Labs label. Stunning lifelike sound: extremely transparent, with incredible immediacy, dynamics, and lifelike instrumental timbres. Get yourself some, and use them for your loudspeaker evaluations. If a speaker is adding coloration, reducing transparency, or both, you will immediately hear it.
