Well, I'm back from my audition of the Mac 501s. It was interesting. None of the equipment was anything I own, so it would challenge me a bit to discern anything. The speakers were from a company called Adam, a relatively new brand, featuring ribbon tweeters and midrange, with built-in powered subs. The front end was DCS digital with a Mac preamp. Nordost cables filled things out.
Despite the $20,000 or so MSRP, I didn't like the speakers. Too bright for my tastes, but the general specs weren't that far off from my Mirage M-3si: same bass (30 Hz) and sensitivity (87 db); the Adams do go to a higher frequency (50 vs. 30 KHz), and the impedance is lower (4 ohm vs. 6 ohm, though the M-3si's minimum is 4).
I tried to ignore the brightness (which gave me a headache) and focused instead on the sound from a detail and nuance perspective, and took some very familiar tracks, 3 of which I always use: "The Strife is O'er" from For God and Country; Hymns of Joy (organ, brass & percussion); "Fanfare for the Common Man" by the Atlanta Symphony Orchestra; "Hallucinations" from Eliane Elias' Cross Currents (jazz sextet); and "Dat Dere" from Sheila Jordan's Portrait of Sheila (vocal, bass). I compared what I heard to my memory of those tracks with my B&K M-200s. The preamp volume was at either 42 or 34 during the session, and the Mac meters never went past 5 watts of output that I saw. I played the tracks 2x, once to get a general feel for the system's sound, then to listen critically.
Basically, the 501 sounded to me like a more dynamic, more detailed B&K. The general sound is quite similar, as both have a tube-like quality, but there were differences. On "Fanfare," I could hear into the brass perhaps a bit more than I remember; a bit more separation among the various horns. The second track from the ASO disc (I snuck this in), the quiet parts didn't seem as quiet as I hear them at home. The decay on the Elias track at the end was longer than I remember. More information retrieved (maybe the Nordost, not the Macs?).
But the big thing was dynamics. During "Hallucinations" there is a Jack DeJohnette drum solo, and here the 501 distinguished itself. When Jack thwacked the drum, it was thwacked. When Sheila Jordan hit a transient on a word, it sounded more live; the "D"s and "P"s popped, but in a natural way, not artificial. By comparison, I remember these sounds on my B&Ks as more polite, less dynamic.
Bottom line: I bought the store's last pair. Now, I must reconfigure my system and figure out what to do with my B&Ks.
VPI, Grado, SME, Pioneer Elite, Magnum Dynalab, Oppo, DVDO, McIntosh, JJ, Mirage, Kimber, Transparent, MIT, Pangea, Wireworld, Shunyata, PS Audio, Furman, Sanus