We know Dolby sets a level standard for single speakers for Atmos Mixing.
Is there a standard level for headphones?..
Well I enquired to every expert I know and guess what there isn’t a standard.
As the headphone volume control is on the other side of the room and well I would like to protect my hearing, I will get out the trusty Radio Shack SPL meter and send -20 dBFS down the line and set it to 85 dBc and see what happens. Please share your thoughts…s
Sadly I’m aware of no headphone standards for pretty much anything with relation to headphones 
. The closest we seem to have on, well, anything is the Harman EQ curve and that is just to try and figure out how to get sound from speakers to translate to headphones.
Part of the issue, volume wise, is it is really variable what a given setting on the dial will produce in terms of output since they vary so much in efficiency and impedance. I mean speakers vary, don’t get me wrong, but headphones are just stupid in the range they have.
As Atmos mixing for headphones is becoming, a thing, there should be something, somewhat of a standard. At least a starting point. I have a RTA, instrumentation mics and a trusty Radio Shack meter so I will play with it.
Years ago there was a head, I think B&K for measuring headphones, if you can afford it. …s
MiniDSP makes a cheaper unit, only like $300. Not sure how good of a job it does but it is something most places could afford.
Really I feel like this is something that would be best addressed by headphone and headphone amp manufacturers. Have headphones specify their output at 1 volt or whatever. Then have headphone amps that’ll let you tell them what that value is, so they can show their volume settings in dBSPL.
Nothing does that though. Even things like the RME ADI-2. It displays output in dB, but it is unspecified what that dB relates to.
Good tip thank you. Not worth $300 for one measurement. Think they would rent or lend one for a day. I can’t even find where they are located on their site.
All headphones come with their sensitivity, good luck converting that into SPL. We are, as always, left to fend for ourselves …s
I did get a good suggestion from my boss, mentor, and friend at Dolby, Ioan Allen, creator of the Dolby Film Program:
I’d use my ears. Calibrate the loudspeaker set-up as you normally would – record a test section – play through headphones and adjust headphone level 'till it sounds the same!
Why didn’t I think of that 
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