I've tried a few different solutions for non-stock cables for the M500. 2.5mm cable adapters, a few different 2.5mm plugs, possibly modding it for 3.5mm or even mmcx. So far nothing has worked yet. The way KEF integrated the stock 2.5mm jack through the yoke hinge itself (and deep) does not make it easy to mod a solution. I'm still working on possibilities, but I'm confident I'll eventually come up with something. If and when I do, I'll be sure to share.