I recently started spending more time listening to headphones when before I was listening almost entirely to speakers.
I noticed that this has affected my ears in some negative ways, including causing mild but persistent high-frequency tinnitus.
My SPL meter (with the cardboard sealing trick) showed that I listened at levels that don't exceed 80dB for the most part (60s and 70s most of the time), other than some peaks in the mid to high 80s. The only exception is some electronica music that I listened to for a short time (maybe 45 minutes total) at a pretty constant 82dB.
I didn't think this would affect my hearing since my impression was that I'm safe up to 85dB. I was wrong... There's some information saying that 85dB is safe for up to 8 hours a day. This is either wrong, or it doesn't apply to listening to headphones. Some other sources say that over 70dB is bad for prolonged listening, and this is more consistent with my experience.
At this point, I don't know what is really safe. I started reducing the levels by 10dB which feels safe to my ears and results in much less fatigue, but I don't know if that's really safe either.
I find that listening at low volume reduces the enjoyment from the music and the level of detail quite a bit, unfortunately. It also makes the differences between amps mostly irrelevant. There are still differences between headphones, but they are also of reduced consequence. Much of the audiophile sound analysis discussed on these forums isn't very applicable to low-volume listening.
I'm wondering what other people's experience is with headphones listening levels. For people who get tinnitus from headphones - at what levels were you listening?
My guess is that there are differences in SPL tolerance before damage happens between individuals and also different age groups; my personal experience is that even 70s with peaks in the 80s is not safe. I'm in my mid forties.