All headphone amps & jacks can drive 600ohm headphones. Just a question of volume. You're still not utilizing the key piece of information here. I know it's tricky. It took me a while, too. The only limitation with a high impedance headphone is how sensitive it is, not its impedance. ANY jack can drive a 600ohm headphone; it's just how loud. Low impedance headphones, though, almost ALWAYS need a near-zero-ohm jack/amp and will tend to sound like they are more vieled, lacking dynamics, rolled off in the lows, and/or especially lacking punch in the bottom end. Driving a low-ohm headphone on even a hi-end but unspecified-impedance jack (its inherent impedance, not what it's rated to be able to drive... that's pretty much meaningless) and complaining about veil or a lack of tightness is more likely indicative of the jack. Otherwise, the headphone will need a response and character that at least partially compensates for bad matching with higher impedance jacks. So yeah, a Grado SR60 might never sound veiled on any jack, but that's due to the fact of its excessive forward upper ranges. Its dynamics will still be affected, though frequency balance and apparent total loss of punch in the bass might not be noticeable because it's so thin to begin with. Again, I have not heard the KRK 6400, but its measurements look definitely above average. Maybe the jack drove it just fine, but I keep seeing this issue again and again with people using things like the Fiio E9 to drive a low-impedance can. That's bad. E7, Grado clones, etc... those are all better matches. Again, ignore the "will drive ### impedance headphones" spec. It means zilch. That's like phono cartridge manufacturers giving a broad range of capacitance tolerance. Unless it's an ultra low-inductance Moving Iron or a high-output Moving Coil, there's just one particular capacitance the phono stage has (unless it's adjustable) and you need to know it to match the right carts & cables (not voodoo, by the way as we're not talking line-level signals). The idea that it's actually high impedance headphones that need the current and electrical damping to be driven without adverse consequences is a myth that's the result of the old Sennheiser signature sound. They might need a lot of voltage and headroom, but that's it.
Edited by Reticuli2 - 9/12/11 at 3:21pm
I much prefer it when people are not afraid of holding back criticism of any headphone, even favorites.
I don't know if I agree with that if so. I do think the AD700 and the first RE0 (IEM) get my vote as the headphones with the least amount of bass EVER! Strangely enough, the bass is better on the AD700 if you're lucky and actually get enough clamping force.
