This time, with the Sennheiser HD598, I have a balanced, fair, and high linearity (see the test on the èreNuméRique site).
For once, there are very sound voice without that bass sounds are erased or that are flattering acute or aggressive.
Comfort is very good. The cable length is appreciable and as connectors, it is good.
Helmets are fragile and must be used with care and store them. It seems to me rather well made.