i don't "do" headphones. I need an "ambient" experience ideally including subwoofer. Speaker placement is also important, but I assume you know that.
Trying to represent a range:
Sharon Isbin "Concerto De Aranjuez", cd. Good classical guitar w/ orchestra acoustics test.
Miles Davis "Kind Of Blue", vinyl or CD. Excellent for horn reference.
Otis Taylor "Truth Is Not Fiction". First CD that blew me away and convinced me it can be better than vinyl. Recorded and mixed specifically for CD dynamic range capability.
Soundtrack album "Casino Royale" esp. the title tune and "The Look of Love". Vinyl. Album was noted as a reference standard for high fidelity and stereo presence in its day.
Vangelis "Earth", vinyl. Excellent spatial separation of instruments. 3-D sound field.
Surprise: Steppenwolf "The Second". Extremely excellent separation and 3-D field placement of instruments, extreme head-room. A fantastic production job on the original pressing and my primary go-to for my system checking. Up there with "Casino Royale" in my opinion.
John Coltrane "A Love Supreme", vinyl or CD. Excellent production and good reference for acoustic piano, bass, and drums, not to mention mention the horn. Good distortion test.
Simple Minds "Alive and Kicking", vinyl.
Eurythmics "Be Yourself Tonight", cd.
Jimi Hendrix Experience, "Rainbow Bridge", vinyl.
My system btw uses 2 AR28b's (2-way 2.5"/8"); excellent for horns and snares/cymbals, Sansui 3-way 3"/4"/10", brings out guitars, vocals, piano midrange and floor toms , and a 12" subwoofer 65w w/ 3-band bypass, I usually set for 250hz . Really brings out "presence" and stand-up bass at low volumes, 26w system w/ 5-band equalizer. Rarely go past 7. ( 9 w/ woofer on 3-3/4 can be heard cross the street if I leave my balcony door open.
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Oh yeah, according to my understanding, magnet size is very important in speakers.