That's a very good and fair review of the Superlux. See also
https://www.stereophile.com/content/superlux-hd-668b-and-hd-681-headphones
Tyll described the Superlux like so: "...sounded like listening to good headphones through razor blades." I think he was being a little kind. Unfortunately these were a hyped up flavour of the month at head-fi several years ago and it seems people still recommend them. They have some really serious faults, only some of which are correctable. Yes, I have owned a pair. I gave it to a charity shop and 5 or 6 years ago and have missed it for zero seconds.
Seriously when you can't stand them any longer (probably it'll be in hours and days, not months or years) try the cheaper Koss. They are vastly superior in every way. If you can do a return and refund or exchange then I'd so so.