Doing some testing with my desktop setup.
foobar2000 v1.0.3 > ASIO4ALL v2.9 > SPDIF > iBasso D12 > RCA > Millett MiniMAX (Tung-Sol 12FM6 tubes, gain 10) > ZX700I used the 12FM6 tubes on the MiniMAX as they're the mid-gain tubes and are the most neutral sounding.
The low 24Ω load is easily noticeable since I can't crank up the volume beyond 11:00. Natural listening volume is attained at the 9-10:00 position.
There is actually a wealth of bass response, but definitely not as deep as the specified 5Hz. In addition, I highly doubt I'll be able to tell if the other end reaches 40kHz.

Returning to the bass, the upper range has more emphasis than the midbass, though it still sounds meaty to me. I can probably say that this is the sweet spot of the ZX700, where the upper bass meets the low mids. Midrange is actually a bit stepped back, compared to... the Denon D1001, for example. The treble does not extend very high up, but the rolloff isn't that noticeable.
Overall the ZX700 is warm and a bit laidback. Isolation is less than 10dB, maybe around 5-7. The short cable is really a treat and makes it easier to pick up this headphone for portable use every day. When I say portable I mean wearing it portably, either on your head or around the neck--this can doesn't fold up so tucking it away will be a chore. A microfiber towel wrapped around it worked well enough for me, though. These belong in the same league as the Denon D1001, Audio-Technica ATH-ES7, M50, and other similar closed portables.