I would say I favor them over the Grado SR225i that I owned and loved for a long time. They of course should sound inferior overall to my PS500's that I really love... wait a minute, are PS500's really better?

I’m way late to this party but you know what? I’m glad I came. Have you been looking for a super affordable headphone but are overwhelmed by all the choices out there? Let me simplify it for you; The Superlux HD668B is exactly what you’ve been looking for. The bass boost starts about similarly on both headphones until 100 Hz, with my Fostex being a bit less full in the root, however below 100 Hz, the TH-X00 continue to climb further and further, and start to roll off much lower than the Superlux that are already really good in this regard, wherefore they have got considerably more sub- and midbass quantity than the cheaper headphones, with an overall more sub-bass-driven sound signature. Due to this more sub-bass-driven signature, they are the even more engaging and fun sounding headphones in the lowest registers. On the FA08 the headphones cable passes in front of my chest and disturbs my hands. On the Octapad disturbs me to play the snare drum. Besides the cable being too tight in both cases. If not because of this short cable, then these headphones would be unstoppable. As with many other headphone manufacturers on the market, Superlux doesn’t exactly overload us with information regarding Bluetooth codecs that are supported by this device. In fact, there’s no information on this whatsoever. As such, we’re left to assume that the current standard, SBC, is the default. This is a shame, since SBC offers the lowest audio quality of current codecs in the mix. When it comes to other technical data, there’s a more reliable reference point. We measured sound pressure levels at a maximum of 99.61 dB SPL, with an average impedance of 38.55 Ohm. This means that just like its big brother, the HDB671 delivers sufficient volume, even when connected to low power outputs. It’s therefore an ideal choice for connecting to desktop and laptop devices, tablets and smartphones. What’s more, its audio transmission range of 20 Hz to 20 kHz covers all frequencies you might require for home studio recording and mixing applications.. Features, Processing & Handling, I used the center "pads" from the Velour aftermarket cups in addition to the Super Lux's own pads, and that made a perceptible difference in taming an EXTREMELY DETAILED (and clean) top octave (above 10,000 or so) My experience was that I couldn't wear them for extended periods of time until I let them run for several days. The bass is well controlled, and it has improved in dynamics (slam, if you will) over time. It's no Ultrasone Pro 900 (It's not even a Senn 600 or 650 either at either frequency extreme) however the mids are quite full and (this word's a little annoying to objectivists, but it's not totally out of place) lush.There is no height adjustment like in traditional full size headphones, and instead you have soft foam “wings” on a spring metal wire which self-adjusts as you put headphones on. This could be hit-or-miss with some people who have big head or curly hair (the last comment actually came from my wife). For me personally, it works quite well since I’m already accustomed to ATH-R70x and ATH-A2000Z, both of which have a similar “wings” headband support. As for comfort, it isn't that good at first, as it has quite a strong clamping force, but it does get better with time. After a while, you can't even notice you're wearing them. This is one of the most surprising aspects of the HD668B. The bass is well articulated, textured and doesn’t show any sign of bloat or woolliness. Mid-bass has nice impact with a fairly fast but natural decay. There’s no noticeable bleed into the midrange. I love the quantity of the bass in relation to the mids and highs. Clearly, the person who added the B (for balanced) to the model number knew what he was talking about. And I was really blown away : the HD-681's produce a sound quality that is unheard of at this price level. Or at 5 times the price.

The HD681 does definitely not really appear weak on the bass at all but the HD668B is the audibly bassier headphone. The HD681 extends slightly better by ca. 3 Hz which is not much and only audible when doing sine sweeps. In the mids and treble, both are more or less on the same level with the HD681 only sounding airier because of its tonal tuning. The HD681’s treble is probably a slight bit cleaner however it is more aggressive as well as edgy.Looking at the earpads, they’re quite large and easily fit right around my big ears. The pads are made from a PU leather with a foam interior. There’s also a sheet of foam covering the drivers so there’s some padding between your ears and the driver covers. When it comes to the bass, the Fostex is cleaner, more arid, tighter, better controlled as well as better layered and reaches deeper without softening towards the sub-bass. In the mids, it sounds more realistic and layered, and its treble is more detailed and refined as well.