Very good audio range on these, i bought them expecting a decent, yet ultimately disposable pair of studio headphones, but they completely blew me away. They do not have a muffling bass (by design) but instead offer superb clarity. I managed to hear new notes in songs i have been listening to for TWENTY YEARS, with all sorts of headphones from cheap mobile earpods to high-priced Sennheisers. These Superlux headphones can compete with headphones ten times their price.
Build quality is of course a bit plasticky, but thats the price you pay (literally) to obtain them so cheap.
very comfortable though, i have been using them for hours on end now in Covid-19 times, as i work from home and have to conference, they stay connected to the audio interface now at all times.
they also function extremely well with instruments. I was very surprised by their clarity when connected to my CDP (digital piano), they sound "very open" not muffled, not artificially boosted.
I highly recommend these. I will easily buy a second or third pair if one of my other headphones break down or even to give as gifts.