Below are some impressions of the Fidelity Audio upgrade cable for the HD800. I was not much of a cable believer in the past but, call it placebo effect if you will, I do hear differences. I very much believe though that it depends on the gear you're using, the kind of music you're listening to, and most importantly how receptive you are to slight changes in music reproduction. The HD800 appears to be the perfect tool to highlight small changes upstream so here is my take on what 6 ft of wire can do.
Transport: iMac + M-audio FireWire Solo
D/A: Yamamoto YDA-01
Amplifier: Lehmann BCL
Headphones: HD800 with over 650hours on them (using stock cable)
Cable: HD800 stock cable versus prototype Fidelity Audio cable with varying multiple gauged conductors and Furutech 601M(R) balanced 3-pin connectors.
Balanced > Single Ended adapter cable: Furutech 602F(R) - APS v3 - Furutech 704 (G)
Music: mostly jazz and rock. I illustrated comments below with some examples. The selection is totally random as I just happened to be playing iTunes in shuffle mode... There are better illustrations for each point, but hopefully this helps you relate to my thoughts if you happen to have some of this selection of music.
Bass:
> Stock cable: very very good. Extends very low and always tight. It is quality bass and I don't miss the deluge of bass I get from the Edition 9. However, for some recordings, you could maybe do with a little more of it on the HD800.
> FA cable: comparatively, it does feel like it is more forward / fuller than the stock cable ("Extraordinary Machine" on Fiona Apple's "Extraordinary Machine", "Tout doucement" on Feist's "Open Season: Remixes & Collabs"). This may actually be due to changes in midrange / treble described below. Drum kicks have more impact with the FA cable (for example "Punk (DJN)" on Avishai Cohen's "At Home", "Sexy Plexi" on Jack Johnson's "Brushfire Fairytales"). It's as if the stock cable can go lower in frequency but the FA cable focuses on the rhythm and fullness of the bass rather than trying to be the most accurate ("Canceled check" on Beck's "Mutations").
Dynamics:
> Stock cable: fair. It's not the most lively headphone in my collection. For that, my Edition 9 remains the reference.
> FA cable: wowowow. Now my HD800 is on steroids! Listening to "Buena" on Morphine's "Cure for pain" and it's not a subtle difference. This track owes a lot to the bass and drum so I guess the FA cable really does something to the bass. Man, this is goooooood!
Soundstage:
> Stock cable: very wide but with a hole in the center (very much left-center-right feeling regardless of Sennheiser's claim for this)
> FA cable: it's so different from the stock at first I thought I was listening in monophonic mode! Basically the soundstage is pushed on front of me. There is much more depth than the stock cable and it is comparatively less wide ("Lost Someone" on Cat Power's "Jukebox", "Wagon Wheels" on Sonny Rollins "Way out west"). The placement of the musicians (or shall I say the intent of the audio engineer behind the recording...) is also much more credible when using the FA cable ("Tuesday Wonderland" on Esbjörn Svensson Trio's "Live in Hamburg") as they seem to be floating with the stock cable. Basically, the presentation is much more speaker like with the FA cable. For concert hall recording it literally feels like you're moving 20 rows back ("Dance Of The Antilles Girls" on Paavo Jaarvi & The Cincinnati Symphony Orchestra's "Romeo And Juliet: Complete Suites From The Ballet")! Furthermore, the tonal balance is warmer - see below - so it accentuates this impression of being further back in the audience. Somehow, with the FA cable, you can more easily portray the depth of the concert hall.
Midrange / voice:
> Stock cable: very good, very natural.
> FA cable: it feels like there's more body to the voice which makes something excellent even better ("Almost Blue" on Diana Krall's "The girl in the other room"). Simply awesome at this stage. The voices are more forward relative to the highs with the FA cable and it's a good thing. It's spooky how realistic voices are, I just don't see how this can further improve ("Chinar Es" on Tigran Hamsyan's "Red hail", "Voices" on Hugh Coltman's "Stories From The Safe House").
Upper midrange / low treble:
> Stock cable: usually very good but clearly it does not forgive bad recordings. Not sure I can say it is artificially enhanced on the HD800 but at least it is more forward than with HD650 and Ultrasone Edition 9 (both of which were not voiced to sound neutral though).
> FA cable: I have a hard time believing cable makes such a difference but clearly the upper midrange / lower treble is "tamed down" with the FA cable. It's consistent across multiple recordings (jazz to rock, voice to guitar). At first, it actually felt like I was loosing something. The HD800 started to sound a bit "slow" in comparison to stock cable, as if it had lost some "snap" / sharpness / edge on transients ("Lies" on Kaki King's "Legs to make us stronger", "Colours of mercy" on Tord Gustavsen's "The ground"). But after going back and forth, the FA cable just sounds more realistic while stock cable is a bit artificial / thin sounding (not metallic but there is like some over-emphasis of that range, for example "Frosti" on Bjork's "Vespertine" or "Dirt" on Rusconi Trio's "Scenes and Sceneries", "15 Steps" on Radiohead's "In Rainbows"). It is obvious on voices (sss sound) and acoustic guitar (listening to "Birds" on Emiliana Torrini's "Me and Armini" when writing this).
Treble:
> Stock cable: very extended up top. The cymbals have a very clear shine. But for some not so good recordings it does feel a bit detached from the rest of the spectrum or some frequencies at sticking out ("Spirit of air" on Marylin Mazur's "Elixir"). Cymbals are of course supposed to sound metallic but it just sometimes sounds a tiny bit off with the stock cable.
> FA cable: it does seem rounded off in comparison. But this is actually not a bad thing because at the same time the treble seems better integrated with the rest of spectrum ("Yesterdays" on Patricia Barber's "Night club", "Valse a l'eau" on Henri Texier's "Alerte a l'eau"). The FA cable results in a smoother presentation. The cymbals no longer sound a bit off / grainy but more like the real thing ("Ad Infinitum" on Carla Bley's "The Lost Chords Find Paolo Fresu") .
Overall: FA cable makes the HD800 sound warmer and more natural. It's as if the stock cable tried to be technically perfect but looses touch with emotional aspect of music when doing so. With the FA cable, the HD800 becomes more musical to my ears. There is less emphasis on transients and more body / fullness to the sound. The difference is not night and day but significant enough to jump at you for each and every recording upon few seconds of listening. The change is on par with difference between amps in competing price range. I suspect the difference between the cables has to do with silver plating of the stock cable versus copper use in FA cable, but Rick might have other theories about this. The balanced to 1/4 inch adapter might also play a role here but I can't evaluate this.
In conclusion, the cable has a very good price / performance ratio in my opinion. Even though I am not taking advantage of the balanced feature, it is a welcome addition to my rig. It is especially welcome for poor / hot recordings as excellent ones sound good no matter what actually. Ahhh, if only Lehmann audio was working on balanced version of the Black Cube (thinking out loud here
).
happy listenings,
arnaud
I only paid for three of them, plus the two headphones. And yes, I do want the best possible sound from these cans, and am willing to spend some time and money finding out what sounds best to my ears in my system. 
