They are open, but I think that shouldn't be a problem in a silent room.
Excuse my raining on the audiophile parade, but I feel there are a few things to be said.
Remember that we are listening to MP3 sources, a far cry from audiophile! In particular, the first thing that MP3 encoding does in the interest of compressing is to clobber the high frequency range, only to have the decoder sort of mimicking it back in.
This means that a planar magnetic headphone’s excellent response and fidelity in the highs (up to 50kHz!) is for naught.
The experience might actually be unpleasant – assuming that your auditory system is young enough to perceive the crappy details in the highs: It so happens that we lose sensitivity to high frequencies as we get older.
In a nutshell, listening to NO’s MP3 source with a 300$ planar magnetic is akin to eating a fast food meal out of Joseon chinaware. IMO.
Besides, all headphones have a fundamental shortcoming which makes many listeners tire rather quickly, become apathic and sometimes slightly nauseated. This because in the production studio, most stereo music is mixed in a way which optimizes the listening experience with external loudspeakers, trying to create a soundstage as wide as possible. To this end, instruments are positioned arbitrarily far apart, without any negative effect because with loudspeakers, both ears are “served” more or less the same sound except that one hears it a bit later, in attenuated and phase-shifted form. In other words, the combination of delay, attenuation and phase shift helps in locating the sound source in our natural way.
In contrast, with a headphone whatever the left channel says goes exclusively to the left ear, same for the right side. So in principle there is no spontaneous cross-feeding between channels to aid in reconstructing a somehow “familiar perception environment”. It seems that this is at the root of headphone listening fatigue.
There have been attempts to correct this electronically, notably by Bauer, Linkwitz, Chan and others. In practice a cross-feed with attenuation and delay is introduced before final amplification. You would not need this special circuit when listening to loudspeakers, of course.
I don’t have an idea about how much of a factor music fidelity is in shaping NO’s efficacy. I can try and find out, subjectively of course. Meanwhile I value the standard Sennheisers for the wearing comfort. Also, following up on the C’s recent recommendation I put together 33 minutes of Gregorian chant. In time for the next session, Wednesday.
FWIW