Source - Sansa Fuze through LOD (with Silmic II 220uf 6.3v caps if anyone cares)
Amp - Mini3, high-performance version, self-built with stock parts
FA003 - 100 hours burn-in, using the leather pads
HD558 - 25 hours burn-in, stock foam in place
K601 - over 100 hours
(all cables stock)
The playing field:
Cornelius - Point
Stereolab - Sound Dust
Outkast - Stankonia
Apples in Stereo - Fun Trick Noisemaker
Gilberto Gil - Gilberto Gil (1968)
Joao Gilberto - Joao Gilberto (1973)
Chopin - Nocturnes
Rimsky-Korssakoff - Scheherazade
Sam Cooke - Live at the Harlem Square Club
and a few others
The FA003 is definitely the most bass heavy of the three, due to the closed design, but it's never overpowering and retains great texture and detail. The HD558 is in the middle - it can thump and does a decent job on hip hop and electronica (or a great job, if you consider it's a mid-tier open headphone). Only rarely for some songs it makes me wish for a bass boost, and it's also slightly loose and doesn't present as much micro-detail and texture of the other two. The K601 has great bass if you're looking for extension and detail - listening to an upright bass on an acoustic song sounds amazing. But the bass is extremely 'dry', and completely fails to groove with stuff like Stereolab.
The FA003 has a great, balanced mid-range that feels very natural - this is a significant achievement in a closed headphone, from my experience. The HD558 sounds very slightly hollow on vocals, but it's hard to tell unless you compare it to the K601, which dominates the others here. The clearest I could hear the difference was with Joao Gilberto's acoustic album. For those not familiar, it's just his voice, his classical guitar and some backing percussion. With the K601 his voice sounds spookily real, with texture and body, like he's singing right in front of you. The HD558 falters here, with the raspiness in his voice taking on a slightly hollow tone. It's hard to explain, but easy to hear. The FA003 sounds natural, in an average way.
I've commented before that the FA003 has slightly sharp highs, but the FA003 cheerleaders dismissed me... I stand by that, and for proof, listen to Frankie Valli and tell me the highs aren't somewhat grating. It's not overly bright or unnatural sounding, but there's a distinct harsh treble energy that can be irritating. The HD558 does sound slightly too bright, by a hair's breadth. Certain vocals come across as sparkly with the HD558, where they sound more full-bodied with the K601. It's a very subtle effect, however. To my ears, the K601 has the best highs, very natural and non-fatiguing.
Because of the isolation, the FA003 seems to have the best detail, but I give the edge to the K601. On complex passages, the K601 ever so slightly outshines the FA003 in separation and precision. But both of them have great texture and make instruments feel real. The HD558 is clearly outclassed in this area - it just doesn't have the same amount of detail or micro-texture, and instruments can slur together slightly on complex songs.
The FA003 has decent imaging for a closed headphone - soundstage is at least somewhat outside of your head and 3D placement is fairly realistic. But it still feels constrained, artificial and claustrophobic at times... it's hard to put your finger on, but something's not right. HD558 had the best imaging of the three, and maybe of any headphone I've ever tried. Soundstage is decently wide but not too distant, and 3D placement was absolutely amazing. Listening to drums, you can pick out where each drumhead is in the kit, and sounds pan from left to right with dead-smooth transition. It can feel hallucinatory sometimes, in a good way :) The only negative was with sounds mixed totally to one side or the other, which seem to come from behind your ear - but with crossfeed it goes back to being amazing. The K601 was a big disappointment. 3D placement was not realistic at all, and soundstage was wide but discontinuous, with a clear gap in the center while left and right sides feel separate from one another.
I just can't get over how fatiguing the FA003 are to me. Maybe it's because of the closed design, but the sound pressure can become intense, and I can't make it through even one album before it becomes uncomfortable (maybe I shouldn't be telling you guys this since it's pretty gross, but last week when I was listening to the FA003 exclusively, I q-tipped out a huge chunk of ear wax, and it made me think my ears were trying to protect themselves from the pressure waves). While I'm listening, I sometimes have to clear my ears like on an airplane. I posted a thread about this phenomena, and tried using crossfeed to remedy it as suggested, but it doesn't seem to make much of a difference. I think I just can't handle closed headphones.
Even though the K601 are stunning with certain genres, the other two sound more natural with a wider variety of music, and I just can't live with a headphone that doesn't groove. If I had the budget/space for multiple headphones, I might keep the K601 to use exclusively for acoustic music... For the first five minutes when listening to the FA003, it sounds like a better, more impressive headphone than the HD558. Unfortunately, it becomes more and more disappointing the longer I listen to it. The fatigue is a big reason, but also the artificial imaging and closed-in feeling started to bug me more and more over time. It's a shame because these seem great on paper, but if halfway through an album I can't wait to take them off, there's something wrong.
In the end, I'm only going to keep one, and it's the HD558. Yes, from a technical standpoint it's a lesser headphone than the other two, but it feels the most natural by a long shot. I'll eventually get used to all the nit-picks I have about the sound signature, and I can overlook the slightly squishy details, because the imaging is just that amazing. If you're looking for an affordable* headphone to transport you to another world, and you don't sweat the details, this is it... but my upgradeitis has not been sated, and now I'm itching to try the HD600. Any ideas about how it compares to the HD558 purely in terms of 3D imaging and soundstage?
*(I was able to get the HD558 for $128 shipped (to Hawaii, by UPS second day air, which should cost over $40 normally but they only charged me $11) by calling J&R and asking them to price match the Electronics Expo 40% off deal)