Granted the HE-300 are not planar magnetics but at USD249 currently, I would have thought there would be more fans.
No love for the 300?
Oh, sorry. When you said you were the new owner of a HE400 I just assumed that was a typo since this thread is about the 300.
HE300s + felt removal mod + pleather earpads = bass monsters. Far from the cleanest bass or the best extension (certainly not even close to the planar brethren HE400 and up) but by golly their bass hits like a baseball bat with the pleather earpads, and the felt removal gives them enough clarity to work well with pleather earpads.
Da fuh that's so cheap, I got mine for like $20 off Ebay back in the day.
IMO you need 2 mods for them to really shine, these 2 mods really synergize with each other.
Kramer mod where you detach the front grills of the drivers and drill a bunch of symmetrical holes (increases midrange clarity and treble presence, removes cupped quality to the sound).
Headband mod employs the cannibalized headband from PartsExpress headphone, and allows the drivers to seat flush to the ears instead of just dangling loosely (increases lower end body, bass extension and tacility, slightly relaxes the upper end so it's not stringent).
The Kramer mod alone is IMO too bright-sounding, while the headband mod alone is too muffled-sounding. Together they give the KSC75s freakishly good tonal balance.
It kinda seems the HE-300 falls in the same category as the Philips X1. Relatively close in price, both open back and full sized. I can't say anything about the HE-300, but I assume the comfort is similar to the 400 by its design. Like you, I would get the HE-400 for its planar drivers from the HiFiMan line, but I think I'd take the X1 over the HE-300. Again, I've never heard or felt one myself, and I'd still like to. But from photos of the HE-300 the X1 looks more comfortable. I've read somewhere that the 300 pads are pretty stiff.