Yep. Quotes:
"If you want to be assured a source will work well with just about any headphone, simply make sure the output impedance is under 2 ohms"
"As output impedance increases
electrical damping is reduced. The bass performance of the headphones, as designed by the manufacture, may be audibly compromised if there’s insufficient damping."
"
THE BEST HEADPHONES ARE DESIGNED FOR THE BEST SOURCES: If you do a quick survey of the most well reviewed high-end headphone amps and DACs, they nearly all have very low output impedances. Examples are products from Grace Designs, Benchmark Media, HeadAmp, HeadRoom, Violectric, etc. It only stands to reason that most high-end headphones are designed to be at their best with similar products. Some of the most highly regarded headphones have relatively low impedances including several models from Denon, AKG, Etymotic, Ultimate Ears, Westone, HiFiMAN and Audeze. All of these, as far as I know, were designed to be used with low (ideally near zero) impedance sources. I’ve also had a Sennheiser representative tell me they design their audiophile and portable headphones for zero ohm sources."
"
EXCEPTIONS TO THE RULE: There are a few headphones supposedly designed for significantly higher output impedances.
I do wonder if this might be more myth than reality these days in terms of audiophile and consumer headphones as I’m not aware for any specific examples. But it’s certainly possible. If so, using these headphones on a low impedance source might cause under-damped bass performance and a different frequency response than the manufacture intended. This might explain some of the “synergy” claims when certain headphones are mated with a certain source. But those “synergies” are entirely subjective—one man’s “bright and detailed” is another man’s “harsh”.
The only way to get consistent performance is to use a low impedance source and follow the 1/8th Rule."
Basically pretty much any headphone is going to be better with low impedance sources.
If you get too much residual noise with a super sensitive headphone and it is annoying, a series resistance can be used effectively in some cases.
Maybe LH will let us know their intention with the markings.