What stands out about these is the sub-bass performance: there's more sub-bass than I know what to do with, I actually have to tone it down a good 4-6 dB and I still get plenty of satisfaction out of what's left.

By contrast with this and with the overly pronounced treble, the upper bass and all of the mids sound lost, pushed into the background somewhere. So overall if you care about fidelity there is no way to use these without EQ. (You will have better chances with the 662 or 662-Evo if you're still after a closed set.)

Dynamics/resolution seems on par with what I've heard from Superlux in the 668B and the 662-Evo, meaning excellent for the price.

Comfort is typical for Superlux - a disaster out of the box - with the clamping force too high (but you can adjust it by stretching them out) and the pads both too thin and too stiff. I have no idea what the other reviewers were talking about calling these good isolators but I found them to be anything but. The pads need to be far softer / more spongy to make good contact all around the ear and isolate well. The way I solved it was to get AKG K240 pleather pads and glue them on top of the stock pads, to achieve at the same time better depth and comfort and isolation (the AKG pads are also too thin to work well on their own).


Bottom line, if you have multiple Superlux options, get these only if you care a lot about sub-bass performance. Otherwise, if EQ is going to be a problem, maybe go for the 662-Evo, which is closer to neutral and also comes with velour pads.

[Initial review contradicted by more careful testing with good headphones; preserved to paint a fuller picture]
 
I got this while under the impression that any external DAC will be better than integrated audio (false, apparently) and while still believing that the usual widely-quoted specs like SNR and THD could tell you the whole story.
 
My best headphones at the time were the Koss KSC75, so I tested it with those: did A/Bs at the office between the office PC and the Q1, then between my phone (HTC One M7) and the Q1. The differences were so small that I couldn't even be sure there were any differences (that it wasn't all just placebo). But I chalked that up to the noisy office environment and forgot about it.
 
Then a few days ago I saw a discussion in a forum where someone said they were disappointed with the lack of sound quality difference made by the Q1 and had to send it back. Shortly after that I found the Geddes & Lee papers alleging (but failing to prove, as it turns out) that widespread distortion measures like THD and IMD are meaningless, and these two new pieces of information put together made me seriously question my Q1 (again).
 
So I did the A/B comparisons again. This time my best headphones were the burned-in Superlux HD668B, which are pretty bright and otherwise flat, and much better than the KSC75, and thus by all acounts should allow the Q1 to shine. The phone was the Xiaomi Redmi 3. And again my experience was that the differences are so small that I can't even be sure I'm not lying to myself in saying that they're there. If the differences are real, they manifest as better detail in the treble and better imaging (narrower positioning of each instrument). But if I'm going to pay money for an extra device of this kind and if I'm going to carry it around in addition to my phone, I'd like its sonic benefit to be unquestionable. And it isn't.
 
So, long story short: don't buy this as a DAC, chances are it doesn't do much that your integrated audio doesn't already do. I for one am disappointed and I'll be looking to sell mine.
 
 
[18.08.2016 Correction]
 
OK, I've taken the time to test this little thing more carefully in a silent environment at night, again with the Superlux HD668Bs, and this time taking care to switch the cables faster so I don't forget the previous sound like I was doing before.
 
As it turns out, when you have headphones with lots of treble extension and reasonable smoothness, you can confirm beyond any placebo doubts that the Q1 delivers better sound quality than integrated audio in at least two ways:
- better treble extension (there's more to hear up there in the "airy" regions)
- deeper soundstage (artists not so in-your-face but sounding like they're somewhere farther back).
 
Putting this together with all the other features and conveniences, I have to say I've changed my mind and I think this is a recommendable device after all. You do get your money's worth considering the price and the improved sound. Just make sure you're using it with headphones that do a good job of representing the treble, both in terms of extension and neutrality, or you could end up hearing no difference relative to integrated audio (like I did and still do when listening through something like the Koss KSC75s - treble too grainy - or the Philips SHP2000s - hardly any treble extension).