Zaikesman,
The adjectives I used, though fairly broad and basic, were chosen because that's my experience with the vast majority of PC's. So if, as you stated, there was a reduced brightness in the longer Van Den Hul cord, how would one explain that same tendency in cords that feature no 'filtering' of any kind?
The answer is in the inductance and capacitance factors that result from increased length. It's no more complicated than that. Longer cords get 'warmer' with every foot you add, although how rapidly you hear the change depends on the specific geometry of the cord. The VDH cable is an outstanding design, with very low inductance, so it's losses in resolution and dynamics should be more gradual as the length increases. Other cords, which have higher levels of Inductance per foot, will yield a more rapid change as the length increases.
A properly designed PC should be resistant to noise, but if the changes in sonics we're hearing are strictly from filtering out that noise, then where are the measurements to back up that idea? I've seen plenty of powerline conditioners that give specs on their noise filtering capabilities, but have yet to see numbers on a PC. I don't think that's coincidence.
IMO, RLC factors rule the roost when it comes to PC sonics. They don't explain everything (like why cryoing 'sounds' like lowered inductance, but isn't measureable), but they seem to get us most of the way there.
Again, JMO.