Hi Folks,
The cable for the K340 is still available under part number 2376K0001. It's the original cable material. We do not have a suitable 'better' cable but as you are convinced about the sound quality of your K340, why change the material? For headphones especially in higher impedance types the cable material is of not so vital importance as e.g. for loudspeakers.
Coming to the second question about specs:
Frequency range: 16...25.000 Hz
Impedance per side: 360 Ohms
Operating power at 1 kHz: 2,5 mW for 1 Pa = 94 dB
Kind regards
service@akg.com