Before I begin, I want to thank forum member jazzerdave for being kind enough to loan these out to me. He didn't even ask for anything in return. Stand up guy.
With my introduction to the electrostatic world via the SR-407 with SRM-252S amp, and it completely blowing me away sound-wise, I started looking to see what was sold new today for an affordable price range (head-fi affordable, not real world affordable, but I digress). The Koss ESP-950 immediately jumped out at me. Electrostatic headphone WITH an amp sometimes sold for less than $700? I HAD to check them out!
Koss is usually associated with headphones that are budget conscious, delivering great sound without breaking the bank. By now you guys probably know how much of a fanboy I am of the KSC-75 and KSC-35. I will always have at least one pair of Koss headphones in my lifetime. The Koss ESP-950 has been part of Koss's repertoire for a few decades, known for their incredibly linearity, well balanced, yet musical sound. The ESP-950 comes bundled with their E-90 electrostatic amp. It uses a proprietary headphone input, so it only works with the ESP-950. The great thing about Koss is that their well known Lifetime Warranty is also applicable here, so if for any reason these fail you, you can get them replaced/fixed by Koss directly. More companies should follow this type of business mindset. Standing behind their products for as long as you live!
Build Quality: Unfortunately, the build quality is without question, the worst build I have seen on a headphone costing more than $100. It literally feels like a $20 headphone to me. The internals could be made out of styrofoam, and I wouldn't doubt it.
Seriously, I don't know what it is, but electrostatic headphones seem to focus purely on sound quality, and not build or aesthetics (at least until you hit flagship level Stax headphones).
Starting with the cups, they seem to be the best area of the ESP-950's build. The grills look decent enough, and feel solid enough. It's all plastic, and not a very good feeling plastic at that. Seriously, it feels like this kind of plastic belongs on no name brand budget cans. The extension bars seem to be the only thing made out of metal, and yet, it still feels/looks a bit too thin for my personal taste. Unfortunately, the arms don't like to stay at the length you adjust them to, and I can almost guarantee that it will set itself a bit more loose than anyone may like. That is, unless you have a gargantuan head and wear these fully extended. The headband is made of some cheap feeling pleather that could stand to be a little more dense inside, but is ultimately quite comfortable, as the headphone is so light and loose, the headband feels like it practically just rests there.
The pads? Oh, the pads. They are made of incredibly cheap feeling pleather of the WORST kind. Seriously, pick out an extremely cheap over ear headphone, and I'm sure the pleather pads would be comparable to the ones on the ESP-950. Despite my absolute hate for these kinds of pads, they are actually not uncomfortable by any mean of the word. Due to how loose the ESP-950 clamps to the head, the pads don't really put much pressure on the skin, so it doesn't induce much if any sweat.
The cable is of the standard flat, ribbon-type cabling found on most if not all electrostatic headphones I have seen. This is a good thing. This basically guarantees no accidental tangling. It's a bit short of length, though it comes with an extension cable of decent length. Unless you sit right next to the amp, you're guaranteed to use the extension cable.
Now, I'm not sure if it's a build issue or just typical of electrostatics (didn't hear it on the SR-407), but the ESP-950 retains some static noise even if unpluged. You literally have to touch the contacts at the end of the cable to make the noise dissipate.
Comfort: As mentioned before, the ESP-950 is incredibly lightweight, and incredibly loose fitting (think AD700 type looseness). While the comfort overall is pretty good, the lack of secure fit makes it a little less pleasing than it should've been. The headband is very comfy, and the pleather pads, while of horrible quality, is a non-issue due to the loose fit.
Accessories: The ESP-950 comes in a very, very nice 'leather' bag, used to fit the headphone, the amp, a battery pack (without batteries) to allow the E-90 to be used on the go, a pair of RCA cables, and 3.5mm cables. If only they spent less time with accessories, and more time with the build quality of the headphone itself, but that's just a personal gripe.
Isolation/Leakage: As expected on open and electrostatic headphones, there is absolutely no isolation or passive noise cancelling. These are not to be used where noise control is important.
Sound: So to the meat of the review. As advertised, the ESP-950 is certainly a very linear, very balanced, and very well behaved headphone. These are among the flattest sounding headphones I have heard, where nothing really sticks out over anything else. The upper and lower ends are slightly rolled off, meaning there is no direct bass energy or treble sizzle. The sound as a whole was indeed quite neutral, with a hint of warmth. There is a very good sense of space and soundstage is decent, but not a stand out over what I've reviewed so far. The ESP-950 is soft sounding, a hint laid back, and polite overall. It's quite the contrast compared to the SR-407 which was quite fast, lively, energetic, and aggressive, while maintaing some amazing clarity and refinement. That's not to say the ESP-950 is muted or lacking in clarity. On the contrary. The ESP-950 is among the most detailed headphones I have ever heard. It's most evident during gaming, from what I experienced. The ESP-950 while not being the most musical headphone, is still very enjoyable. Not sterile/clinical, and not colored in any real way.
Bass: While the bass is slightly rolled off at the extreme lower end, it's not a steep roll off. With bass heavy music, the bass has a surprising amount of presence. It's a bit soft hitting and slow in the bass compared to the SR-407 which was very agile and punchy, but rolled off quite a bit faster. The ESP-950's bass overall is enjoyable and atmospheric, but doesn't bring immediate attention to itself. It could stand to gain a bit more speed and punch, but it doesn't 'sound' bass light by any means, just somewhat polite.
Mids: This is easily the biggest strength of the ESP-950. The slight warmth and linear frequency aside from the bass and treble roll off, ensures the mids are slightly forward and immediately engaging. Though not as sultry and intimate as the LCD2, it does have a similar organic tonal quality to it. Basically, voices sound very realistic/natural. If you have a lot of music that relies on vocals more than anything, the ESP-950 will not disappoint.
Treble: The treble is ever so slightly rolled off, but it's not veiled or muddy. It gives the ESP-950 a pleasing clarity to the upper range without any of the harshness found on headphones with more treble quantity. Among the most pleasant treble presentations I have heard. Not too rolled off, not too sparkly. It's in a good place. Trebleheads may want a clearer treble presentation, like that found on the SR-407 however. In this aspect alone, the ESP-950 takes on a more musical than realistic approach.
Soundstage: As previously mentioned, the soundstage while not being a stand out, is quite natural sounding in size. Depth isn't an exact strength, but there is an appreciable amount of width, with great instument separation.
Positioning: For gaming, the ESP-950 stepped it up with Dolby Headphone. The soundstage was a very good size, and while the depth still wasn't amazing, it was pretty easy to poinpoint directional cues. Space between direction cues was very good, allowing for no confusion or distractions.
Clarity: Again, like the HD650 and LCD2, the ESP-950 is slightly on the warmer side of neutral, yet like the other two, clarity for gaming was very, very impressive. Actually, if the soundstage was larger, and depth was better, these may have been right up there with the AKG K70x's in terms of god mode inducing clarity and performance. If I had to rate the clarity for gaming alone, it'd be an easy 9.
Amping: A non-issue as the ESP-950 comes with it's own amp, though people do take the extension cable and mod it to allow the ESP-950 to be used with more robust Stax amps. In any case, the E-90 drives the ESP-950 quite decently based on what I'm hearing, though the amp's volume control is an absolute pain as each side has it's own independent volume control, so you'll have to match by ear. To get around having to constantly re-adjust with different sources, I set it once, and controlled the volume with my Compass-2 (used it as a pre-amp). In terms of gaming, Mixamp owners will probably want to set the volume once (on a high decibel level) and adjust volume with the Mixamp (or other DH devices). The E-90 is also not the quietest amp, with some very slight background noise that occurs randomly.
Value: The prices fluctuate wildly, but if you can score them near the $700 range, they are an incredible value. Electrostatic headphone, amp, bag, portable battery pack. All your bases are mostly covered. The build quality doesn't not compliment it's price, however.
Final Impressions: Those looking for an incredibly well balanced, linear, and neutral-ish headphone, may find the ESP-950 to be a serious contender for your money. The ESP-950 favors it's balance and faithful representation of sound over musicality, but it remains a fine bridge between the two. For gaming, it is among the best for competitive gaming with very few faults, and it's full sound makes it a very good headphone outside of non-competitive use.
Final Scores...
