I've owned my pair for almost a year now, using them to monitor my guitar and bass played through my Scarlett Solo audio interface using the Bias FX plugin. The audio quality is decent, nothing outstanding, but within the price bracket the HD-681 delivers.
However I would recommend these for guitar rather than bass players, as the low end can become a bit muddy. However, this is comparing a Fender Strat to a more inexpensive Harley Benton bass, which could also affect the comparison. Yet, keeping this in mind the lower register is somewhat lacking in regards to fidelity in comparison to that of the guitar.
For other audio purposes, I've also used the headphones for listening to music on Spotify and on YouTube -- performance satisfactory, nothing mindblowing but decent -- as well as for gaming. I was positively surprised by the headphones' performance for gaming purposes (specifically, FPS games such as Battlefield). The stereo image is surprisingly good and a definite improvement to the gaming headphones I had been previously using three times more expensive than the HD-681. Thus, I would go as far to say that the headphones far outperform as headphones for gaming, however the lack of an inbuilt microphone is a feature the headphones lose out on proper gaming headsets.
To summarise, my experience with the headphones has been overall a positive one. I would consider replacing them at some point were I to work more on recording / producing music digitally or if I needed a set of headphones better suited for Hi-Fi consumption of music. However, so far the HD-681 has well served its purpose as an inexpensive pair of headphones for monitoring guitar and bass. Definitely worth the purchase and I would probably get a new pair were I to lose the current ones.