I have a smartphone now and want to listen to music via that, but don't want to use my Sennheiser HD600 with the cable tangle etc. I will keep them as spares. Which bluetooth headphones will give be the closest sound to my trusty HD600 cans? I don't intend to listen outdoors, so I don't really need noise cancelling. I do like the open back designs and I do need them to be really comfy, for extended listening. Essentially, I need a pair of bluetooth HD600 and I don't know much about wireless Sennheisers, or any other make. I do like the slightly lean sound of the HD600 and the vocal quality. I don't want a bass hump, especially in the upper bass region. Nothing 'full' or warm sounding. Thanks.