OK... brace yourselves for audio-snob-magazine meaningless jibberish.
K701: Overall accuracy, imaging, soundstage. Love its clean, accurate, textured and revealing bass. Its bass is a "dry" presentation that is a nice contrast to my RS1(dynamic/impactful/fast) and HD650(slobbery/smothering/syruppy) bass. At 65 ohms its not too high or too low, its a good Z-match for a lot of different amps... although its not sensitive so it needs more power than any of my other cans to either play loud or reach its dynamic potential. Amp / source properly and its weird upper midrange resonance/harmonic content will reward you.
HD650: For its overall warmth, relaxed non-fatigue-ing presentation. A good complimentary can to Grados and AKGs. Good image / soundstage, but not quite as layered as the K701. The RS1 puts you on stage infront of your guitar cabinet, or sitting on the drum-throne behind the kit. The K701, you're the lead singer front and center stage. Guitar cab on the right, bass cab on the left, Keyboard PA right next to bass cab. Drum kit fills the venue with natural acoustic reverberation and note decay. Crowd is cheering and chanting in front of you. The HD650 is vintage 2CH stereo at its best. Kick back in a leather recliner with McIntosh tubes and vintage Marantz filling the room with Alan Parsons, Pink Floyd and Jethro tull.
Koss A250:Love its brightness, upper midrange/treble boost. Good for revealing details in vocals and solo instrumentation. Nails on chalkboard punishing/brutal though with poorly recorded material. It also has a slight deep bass boost, by about ~2 db only around ~50 Hz. Decent imaging and soundstage, although a step down from the HD650 in this regard. As its brighter presentation gives it a more closed in image. My brightest sounding headphone by far. Awesome synnergy with my Earmax tube amp. At 65 ohms and high sensitivity, its a good match for a lot of different amps, and unlike the K701 does not need a lot of wattage to play loud or dynamic.
K240s-55: Overall solid-affordable performer. Warm-ish semi bass heavy, with some great sounding midrange tones. Very good soundstage image for this price range. Still my go-to can for DVD movies straight out of the Denon home theater receiver. For decades an industry standard in recording studios around the world. So the sounds you are hearing are the same ones the musicians and engineers heard in the mastering sessions... particularly the 600 ohm model.
Edited by kramer5150 - 3/16/14 at 10:09am