I just purchased these and have been thoroughly enjoying them. I bought a stock HD650 cable because I needed the extra length and everything I've read confirmed they used the same connector. After the new cable arrived I compared it with the one that came with the HD6xx and I now see that the cable it shipped with has groves on all 4 sides of the connectors which match protrusions/guides (presumably) molded into the earcups . The old cables (including those pictured in marketing material) had no such groves. Was this a recent change and are other cables no longer compatible with the 6xx?