Hi, I'm new here and I hope you guys can give me some info on this.
I've been thinking about buying DT 990 Pros, the 250 Ohm ones. I've read that headphones with that high impedance would require a proper headphone amp to drive properly, and to my understanding driving headphones means supplying them with adequate voltage so that they can output loud enough volume, right? The thing is, my dad owns the same pair and I managed to test them out today with various setups. Anyway I first tried them with my iPod classic, and to my surprise I could up the volume to definitely loud enough levels, granted the volume was pretty close to max but still. Even with quieter vinyl rips I didn't need more volume than what the iPod could offer, and the headphones actually sounded fantastic with it. Through speakers they sounded pretty much as good, a bit different since they were active speakers (more low-end, a bit recessed mids), not really worse or better.
I suppose my question is, if you can achieve loud enough volume even with an unpowerful source like an iPod, is there any need for further amplification? Is there still some limitation that the low output impedance of the iPod has on the DT 990s, and thus I'd need a good headphone amp to unlock their full potential?