High end headphones

I have some Sennheiser 580s which are like an older version of the 650s with similar 300 ohm impedance, which is pretty high. They are hard to drive, not because they need more "power" (their efficiency is actually pretty high), but because they need a high voltage to drive a small current through the high impedance. It's often impossible to work out from tech specs whether a given audio interface will do this. My previous interface (UA-5) was turned up to max all the time. I recently bought a Presonus 44VSL as it has a particularly high headphone output amongst other reasons and I only need the volume on 50%. From what I read about Scarlett 2i2, you will probably end up with that turned up to max as well with the 650s. Lots of people seem to use relatively cheap headphone amps. I just wanted an all-in-one solution.

+1! I check the internet anyway but only try negotiating if there are unreasonable differences. In most cases we've found a fair solution hitherto.

I'd love to try Beyerdynamic T90's - but there just aren't any to try in my city. Tried everywhere. Even Sennheiser's are hard to find at the better quality levels.  In Ottawa, you are pretty much stuck ordering, trying, and returning if they don't work for you.  No stores seem to stock high end headphones here - unless you call beats high end. So Internet research is critical so as to not waste everyone's time.

Thanks for all the comments! They are very helpful.

I posted this before.
Useful advice for buying headphones:
Frequency response: https://www.youtube.com/watch?v=eyVV-O3969c
Impedance: https://www.youtube.com/watch?v=YMqlU2rUCqQ
Sensitivity: https://www.youtube.com/watch?v=Cp714h0PAAw

Wow - nice gear! I'd never heard of ALO - looks like they do good stuff indeed.

For Windows users (I  know you're using a Mac) that ALO DAC/amp might not be ideal for live playing of Pianoteq etc, because I don't see any mention of native ASIO drivers.  ASIO4ALL may well produce usable results, but for the very best latency I think Windows users should strive to use audio interfaces that have native ASIO drivers. (I know many of us are using ASIO4ALL quite successfully though)

From what I can gather, latency just isn't an issue on Macs, regardless of whether using internal audio interfaces, or USB/Firewire etc.

Greg.

From what I know about the Windows driver model for Vista and newer, there is no such thing as "native ASIO". ASIO is almost certainly an emulation on top of WASAPI nowadays, which potentially has a slightly better latency than ASIO4ALL which emulates on top of WKS, which in turn is probably emulated through WASAPI as well on Vista+ (might depend on the driver).

"New" real-time software for Windows should just use WASAPI and be done with it, IMHO. The WASAPI 'exclusive' device mode offers good latency and stability, and if compatibility with dinosaurs like XP is not a concern there's just no reason to bother with legacy APIs. If everyone were to use the newer APIs, then latency probably wouldn't be an issue on Windows, either.

It seems that Pianoteq does support WASAPI, actually, though not in exclusive mode. This was the answer I got from support not too long ago:

Where the benefit could lie in offering WASAPI but only in shared device mode, I cannot even guess. But my Cakewalk Sonar does support WASAPI, and quite well at that, so I always have the option of just using Pianoteq as a VST.