This and That:
The pleather case with serial number badge and magnetically closed lid looks and feels very nice but isn't exactly dust- or moisture-proof.
The ear pieces are tiny.
The "vents" in the rear are Helmholtz resonators.
Proprietary ear tips.
Cables not replaceable (bit of a pity for the price). Very short cable. Quite heavy and large y-splitter. Generally, I don't find the cable to match the price. The green and black Kevlar fibres are nice but don't distract from the fact that the cable feels relatively cheap. This is further enhanced by the fact that the bend protection at almost all transitions of the cable is practically sub-par. Sorry, but I'd expect better for the price.
Comfort is good.
The fact that Sennheiser has designed the IE 800 in such a way that it can only be inserted into the ears with the cable facing downwards is quickly noticed. Not only is the entire cable quite short, but also the part above the Y-splitter, making it much more difficult for the user to carry the cable over the ears, which makes the fit safer and minimises cable noise. Wearing the cables over the ears is still possible though, albeit not intended by Sennheiser.
Sound:
I'm using the largest included, round silicone tips.
With its mostly flat impedance response, the IE 800 isn't particularly picky when it comes to output impedance.
Tonality:
V-shaped, just like most of Sennheiser's in-ear models.
Very powerful bass with a healthy dose of powerful upper highs. V-shaped tuning mainly highlighting the outer ends of the frequency range.
Elevated sub- and midbass. Upper bass emphasis, although to a lesser degree.
Bass starts to rise slowly beginning around 550 Hz, reaching its climax just below 80 Hz with an emphasis of about 10 dB compared to an in-ear with diffuse-field flat lows, such as my Etymotic ER-4S/the ER4SR. Extends into the real sub-bass without any roll-off.
Lower mids are only slightly fuller; there's no real bloom/spillage from the bass, although my IE 800 isn't as "sub-bass-only"-focused as my Shure SE846 whose bass emphasis concentrates mainly on the real sub-bass whereas my Sennheiser IE 800 peaks already in the higher midbass.
Compared to the lows and highs, the IE 800's mids are more in the background and rather distanced, although not thin sounding.
Midrange balance is done well and appears natural; apart from some pleasantly added warmth to very low male voices, the rest of the midrange is reproduced realistically, with a plausible and accurate timbre.
Due to the bread emphasis of the upper highs however, sibilants are also somewhat accentuated, although they don't sizzle too much.
The area between 2 and 5 kHz, therefore also the presence range, is definitely recessed and adds relaxation to the sound, something which is quite common for a v-shaped tuning to ensure that the in-ear sounds fatigue-free and effortless even over a longer period of time.
Above 5 kHz, the level rises again and forms a wide, bright emphasis between 9 and 14 kHz, that is responsible for the IE 800's high frequency sizzle in the upper treble, wherefore cymbals sound a little "stretched out".
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At home, where I mainly use quite neutral in-ears and headphones, this tuning is definitely too "spectacular" and gimmicky for me. On the go, in connection with a low volume setting, the tuning fits better, because masking effects by the environment are compensated due to the strong bass. The sound is still not completely realistic, but appears less "gimmicky" than when one's listening in a quiet environment.
Nevertheless, I would have personally welcomed it if Sennheiser had taken a more natural direction in terms of tonal tuning with their in-ear flagship, instead of implementing a tonality not much unlike that of their cheaper models.
Nonetheless, even though cymbals could be reproduced more realistically and less "spread", for a "spectacular" or fun v-shaped tuning, there is nothing really wrong about the IE 800, especially and thankfully because its midrange sounds natural.
Resolution:
You have to leave one thing to IE 800 - for an in-ear with a dynamic driver it is technically quite impressive. In my inventory it is definitely one my best dynamic in-ear on the technical level. Nonetheless other manufacturers haven't been lazy either and released dynamic driver in-ears that are similarly convincing on the technical side but cost a good bit less.
The IE 800 has got a quite fast, tight bass for a dynamic driver in-ear and especially high control. While it sounds not as tight and fast as the best closed-woofer BA implementations, it is one of the fastest, tightest and most controlled dynamic driver bass implementations that I have heard, beating many other dynamic driver in-ears, wherefore it is somewhat comparable to in-ears with large or back-vented BA woofers.
Sennheiser's dynamic in-ear flagship also performs more than well in terms of detail reproduction and offers a very coherent presentation as one would expect from a single driver.
Midrange and treble resolution barely lag behind those of a good mid-priced multi-BA in-ear. Even when it comes to speech intelligibility on busy tracks, the IE 800 doesn't show a weakness, even though most Multi-BA in-ears are still a bit ahead here, albeit not at a considerably.
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Whether the IE 800 is worth its price or not is up to one's personal perception. Speaking for myself, I think that based on performance, it was (although only just) when it came out, as it is definitely a dynamic driver in-ear with really good technical performance, however even back in its day and when I bought it, which was in 2014, the total package with the sub-par cable didn't represent a good value. And as mentioned before, nowadays there are technically really good dynamic driver in-ears on the market that cost a good bit less but are technically about similarly good, such as iBasso's IT01 or DUNU's Falcon-C.
Soundstage:
The spatial presentation of the IE 800 is somewhat distanced - the in-ear does not place the user directly in the centre of the action or directly in front of it, but creates one or two rows of distance. Nevertheless, a wide stage is created which goes beyond the basic width of my eyes and ears and reaches about to my shoulders.
Individual instruments are separated and positioned accurately and precisely - you can always locate where a tonal element has been placed.
The IE 800, on the other hand, does not necessarily offer an abundance of spatial depth, but only generates a rather moderate depth in my ears. A little front-back action is noticeable, but no clear separation of the individual levels from each other.
All in all, the IE 800 definitely offers a good and precise spatial presentation, but isn't very three-dimensional to my ears (it lacks some layering for that) although it doesn't sound completely flat in terms of layering.
Conclusion:
Fun, engaging v-shaped tuning with natural mids, even though the upper highs could be more realistic (spread sounding cymbals). Really good technical performance for a dynamic driver in-ear. Short, sub-par appearing cable for the price with improper strain relief; not replaceable (except for the section below the heavy y-splitter).