LCD-3
Ruler-flat bass to midrange, exceptional imaging (though condensed soundstage IMO), and rolled-off treble, also IMO.
I love the LCD2/3 and consider them among my favorite headphone but I would respectfully disagree with you on the description of their sound.The LCDs sound great though not "simply" flat in the bass -midrange. They also do not just roll off in the trebles. Their frequency response are far more complicated than that, which makes them so enjoyable and musical. Below is an estimate of the LCD frequency response based on what I "hear" from specific instruments and voices, not based on measurements..
A. The LCD2/3 are flat but both up by at least a few dBs in the deep bass (about 20-50 Hz) resulting in a solid "body" to the bass to use pipe organ term.
B. The sound is up again a few more dBs above 0 from the mid-bass through the upper bass and to the lower mid-range (50-300 Hz) resulting in a "full" (or slightly ripe) bass..
C. The LCD2/3 then roll off sharply if unevenly below 0dB from about 1KHz or so (flute) and is down by at least 5dB around 2-5KHz in the upper end of the midrange (picolo; string & voice overtones) robbing the sound of some "presence." On the positive side, the LCD2/3 have minimal problems with sibilance (5-10K).
D. By 10KHz (overtones for violin, woodwinds and brass; cymbals), the LCD is considerably rolled off by probably more than 10 dBs robbing intruments of some richness and sheen (reduced overtones)..
E. Fortunately, the LCD response is back up to near neutral or flat (0 dB) by 20K, restoring sonme of the much needed air to the sound.
C & D may be the reasons why some --I include myself in that camp--find the LCD sound a little dark, not unpleasant or un-musical mind you, just dark. Many find this dark, sweet, caramel-coated sound addicting. I do on some music but not all.
I do not intend to contradict you on the great sound of the LCD2/3, I just want to state that their sound is far more complicated than just flat in the bass-midrange and rolled off in the trebles. I do completely agree with you, however, on the small soundstage though I can find no simple explanation.
Cheers,
Justin_Time (ST)