@n80, my curiosity having been piqued by this discussion, I’ve just performed an experiment that seems relevant.
First, I listened to some dynamically compressed pop music (i.e., music having relatively little volume variation during the course of the selections) using the closed-back Audio Technica headphones I referred to earlier. I did this from a computer, via an Audioquest Dragonfly Red USB DAC/headphone amplifier. I adjusted the volume to a level that is perhaps slightly higher than most of us would listen at, but that would still be safe and comfortable for most of us.
I then took the phones off of my head and placed the two earpads snuggly against one another. I found that I was able to hear the music VERY faintly within a distance of about three feet. I then separated the earpads, to create what I believe would be a rough approximation of what would be heard by someone in the vicinity of a user of open-back phones, that are being listening to at a similar volume level. I could then easily hear the music at a distance of 15 feet, and I could hear it faintly from another room at a distance of about 20 feet.
I then played the same music, at what I perceived to be about the same volume level, in my main system using my Stax electrostatic headphones. That was done using the same source material stored on the same computer, communicating it to my main system wirelessly via a Squeezebox. The Stax phones are of course open-back. Also, with those phones it is not possible to place the two earpads together. After removing the phones from my head I found that I could easily hear the music at a distance of about 20 feet.
All of this was in a very quiet environment.
The bottom line: The sound isolation provided by the closed-back design of the AT phones makes a world of difference.
Regards,
-- Al
