Pros: Warm, good bass, feel sturdy, good aesthetics, detachable cable, nice included accessories and case
Cons: Not actually circumaural, cheap cables, overbearing clamping force, highs can be shrill
I was overall unimpressed with the Focal Spirit One cans. I'm hardly a connoisseur of headphones, but I was let down a bit by the sound and the manufacturer's advertising.
I compared these to my reference headphones, which are at the moment a pair of Sony MDR-V6. I would be comparing them to some Denon AH-D950s from ~2000, but they are (alas) broken. My overall impression of the Focal Spirit One is this: good, but you can find much better for less money.
I found the sound to be pleasant - it leans toward warm with very pronounced bass characteristics; the bass sometimes got in the way of the rest of what I was listening to, but always felt tight and accurate. I was disappointed that the low end was not as fulfilling depth-wise as the Sony's - the Spirit One's bass did not carry as low or as smoothly, but was certainly emphasized more. It was easy to hear the difference between the booming sound of the Focal and the quieter, deeper feel of the Sony. I did find the mids to be much more present in the Spirit One's as compared to the Sony's - where sometimes the MDR-V6 could leave me wanting to hear more, the Spirit One's filled in the range well. I did find the Focal set to be shrill at times on the high end, but never tinny - the Sony's were more accurate at the highs, but the Focal's were louder and fuller sounding with snares, etc; I couldn't seem to hear as much of the small details in the high end on the Focal. I missed the accuracy and very neutral response of the Sony's, all in all - the sound from the Focal Spirit One is somewhat boomy and loud, emphasizing the lower end of the spectrum. The sound stage was quite compressed, as expected from them being closed - the feeling was one of isolation and a very small venue. I listened with an LG G2 with/without an amp (analog), from a Lenovo T430s without an amp (analog), and from my desktop with my portable amp (SPDIF) and my Yamaha receiver (SPDIF). I found that the sound was most certainly enhanced by having an amp (bass is a bit out of control without one) - portable amp was a FiiO E07K; the Yamaha was not a noticeable improvement over the FiiO, overall.
The Fit and Build:
The Focal's hurt. I have large ears, and Focal bills these cans as over-ear (circumaural). Let me clear that up right now: they are in no way circumaural, with the possible exception of those under 10 years old. Adult ears will not be enclosed by the pads - the pads rest on the ears, most certainly, and thanks to the huge clamping force they hurt after only a few minutes. The pads are by no means soft, really, as they are quite stiff and smooth - unknown if they would soften over time. Headband has plenty of adjustment, the set is light and conveys a well-constructed feel, and the aesthetic is polite and inoffensive, if modern. I did not like the included cables - they feel cheap and low quality, though they seem to have a textured sleeve around them which will probably lend them durability. The cables seem to stay in place nicely and aren't loose at all. I also noticed no rattles or unexpected vibrations. Ambient isolation is superb, thanks in part to the clamping force and deep, stiff pads.
I was left wanting after listening to the Focal Spirit One. The Sony's trademark neutrality was missed greatly, the un-amplified playback was miserable (although expected), the fit on the ears was painful even for short sessions, and the highs were not consistent.