I have a UR28M and the specification for headphones says Maximum Output level 35mW @40 ohms. I want to choose a new pair of headphones but I’m not sure what the impedance should be. BeyerDynamic possibilities are: 16 ohm, 32 ohm, 80 ohm, 250 ohm, 600 ohm. Should it be as close to 40 ohms as possible?
Regards, Richard.
Hi Richard
There are a few things to know about Headphones. The Ohm Thing. The Sensitivity Thing, and the Max Input level Thing.
The last one is how loud the cans can get, without distortion.
the sensitivity is how effektiv the input signal will be transfered by the headphones. for example. a Headphone with say: 32Ohm and 112dB/SPL is about double as loud, as a Headphone with 32Ohm but a sensitivity of 96dB/SPl. So the Sensitivity is important.
On the other Hand; if you have two Headphones, both with the same sensitivity of say 96dB/SPl but headphone 1. with an impedance of 32Ohm, the 2. with 80 Ohm, the first one will be much louder.
The Headphone amp of your UR28M is to weak to drive headphones with 250 or 600Ohm loud enough. Therefor you´ll need an external powerful headphone-Amp or so. Maybe a Headphone with 80 Ohm might be O.k. for your needs but…. this is a very personal preference and you hafe to try for yourself.
→ You can use headphones with less than 40ohm, lets say 16 or 32 Ohm with your interface without any problems.
The Spects for your interface tell you, how loud they get with an headphone with in impedance of 40ohms. But how loud are 35mW, and on witch frequency and and and. so check for yourself or get informations about witch headphones are used by other people with an interface like yours.
For example, for tracking i use cheap AKG Cans, with closed backs, 32Ohm with 112dB/SPL a they can get loud enough for this purpose with my UR22 MK2.
For Mixing, i use monitor speakers, and late at night my 32Ohm 92dB/SPL open Cans. For Mixing they are loud enough for me! For Tracking they have not enough power for working with microphones, and they are open so they would bleed to much sound when working with a microphone. For playing line in signals, bass guitar, or Keyboard they are loud enough for me.
So, as higher the impedance goes, as more problems with volume you can run in to. and don´t forget about the sensivity.
Long story sorry. and as often with audio stuff, not that simple. but i hope you´ll understand what i was trying to explain here, and yes! english is not my nativ language! 
greetings
dongrappo
Thank you for responding.
Looking at 3 BeyerDynamic headphones:
(A) DT770 250 ohm, SPL 96dB, max 100mW
(B) DT770 80 ohm, SPL 96dB, max 100mW
(C) DT770M 80 ohm, SPL 105dB, max 100mW
So (A) is louder than (B), and (C) is louder than (B), if headphone amp has sufficient power?
I thought that the higher the impedance, the lower the loudness, so (A) would be quieter than (B) ?
I assume that the quality is OK so long as there is sufficient power, and more power is needed for higher impedance phones?
You say that 16 or 32 ohms is OK, but I always understood that having too low impedance will blow transistors ?
I’m thinking that the DT770M 80 ohm is the one to choose.
Regards, Richard.
b will be louder than a. the 250 ohm is hard to drive. c will be the loudest in your list, and might be loud enough.
the low impedance problem is with speakers i don´t know the technical specifications for your ur28m. but many people uses headphones with 32ohm an lower impedance without any problem. like me.
i think the ur28m headphone output is much higher than mine. so, maybe you´ll try for yourself, or maybe search in this forum or in the world wide web for better info. i told you all i know.
regards, don
maybe this will help you. the 3. post https://www.gearslutz.com/board/newbie-audio-engineering-production-question-zone/836718-safe-impedance-headphones-audio-interface.html
Don,
All the specs say for the UR28M is: Maximum Output level 35mW @40 ohms.
For the UR22 it’s: 6mW @40 ohms.
I don’t know why Steinberg don’t just recommend an optimum headphone impedance for the UR28M, after all they designed it.
Thanks for your help.
Finally bought the 80 ohm DT770. It’s louder than my existing 8 ohm DT100.