KOSS Headphones Noise Cancelling

This is a pair of headphones made by KOSS.

Regarding the sound quality balance, my impression is that it leans quite heavily towards the high frequencies, with a weak bass presence. However, the resolution in the high frequencies is relatively high, making it suitable for monitoring purposes such as instrument playing, or for use in wireless communication. According to online searches, there are also modification methods to amplify the low frequencies.

It's a passive noise-canceling type, which physically increases sound insulation to make surrounding sounds less audible, and I feel the sound isolation is quite high.

Be aware that when you turn up the volume, there will be some sound leakage to the surroundings.

The knob on the headphone housing is the volume adjustment dial. When adjusting with the knob, the sound may become difficult to hear due to poor contact, so it's probably best not to fiddle with it too much.

There is a mono/stereo switch on the cable. This also has poor contact, and sometimes the sound becomes difficult to hear in stereo.

I believe this is an early model with a large KOSS logo.

It looks cool, but it's a niche item that requires specific usage scenarios and is beyond my capabilities, so I am putting it up for sale.