At the headphone end, it is a stereo 3.5mm jack. You can use the stereo jack in either earcup.
Since the same left/right signal is delivered regardless of which jack you use, we know they are in parallel. So, I bought a stereo splitter and a second cable. I'm hearing two benefits to this double run of cabling.
1. In quiet passages there is more detail.
2. Bass is truer but is not emphasized. Kick drums and toms have better impact (dynamics). The sound is fuller, but not tubby. Same with electronic bass. Upright, acoustic bass is cleaner, not a fuzzy buzz.
