Originally Posted by electrathecat
Though you guys might theoretically be thread-jacking, I love this discussion (it's quite informative) and hope you guys keep it up. Since we're being technical, I was curious as to what makes the Omega IIs harder to drive (i.e., more power hungry) than the HE60s? Does this power-need difference lead to any impact on sound quality or character?
The SR-007 is much tougher to drive as the distances in the drivers are greater. The He60 drivers are just 4 pieces of molded plastic stuck together with more then a dozen of plastic screws. The conductive elements are all painted on and the diaphragm is glued to one of the stator structure, the back one to be precise. The conductive paint is nearly in contact with the film but it is so tightly stretched so that won't happen.
The SR-007 uses PCB material as stators with the side facing away from the diaphragm completely copper extruded and the electrodes then gold plated. The stator is thus fully insulated and the diaphragm can't arc. The diaphragm is fixed to a ring structure and all encased in a very sturdy enclosure that is designed to transfer all extra energy into the head. The He60 driver is simply clamped in place by two pieces of rubber, not a bad way of doing it but far from ideal.
The SR-007 driver is larger, the diaphragm isn't as tight and the housing is much better so that all leads to better bass handling but since the drivers are so far apart you need much more voltage to get things going. There are very different opinions surrounding the D/S spacing and it's correlation to bias voltage and how much voltage is needed on the stators and there is no right answer here.
One thing that owners and users should know is that while the bias voltage can be similar there can be other factors to consider, namely how big is the bleeder resistor. The bleeder controls the constant charge mode on the diaphragm which keeps it in line and lowers the distortion. Sennheiser used 10M while Stax uses 5.1M and that's why the old He90 phones need the extra resistor on the bias line in series with the one inside the amp.
To my ears the He60 is a very good headphone (listening ti it right now :he90
and I do like it more then the HE90 but it's far from being in the same class as the SR-007. There is an obvious midrange coloration and the highs, while clear and extended, are prone to reveal sibilance. No big issues but as a whole they are a Tier 3 phone in terms of performance but a nr.3 of my favorite phones of all times.