Koss ESP/950 Electrostatic Audiophile Over-Ear Headphones, Black

The ESP-950s are very nice electrostatic headphones, and if you can get them for hundreds off of the $1K manufacturer's suggested price, as I did, they are a great value. Pros: They sound great. Very accurate from bass through the mid-range, with an emphasis on mids. The bass is excellent, but not overdone -- these aren't for bass heads. They love human voices, guitars and pianos. They are lightweight. They come with their own amplifier (you have to use it, or a Stax amp with a modified cable). The whole rig is "portable" in the sense that you can run the amp off of batteries, but it won't fit in your pocket, so I would classify it more as "movable" from room to room, and flexible because you can drive it from an MP 3 as well as any source outputting analog via RCA jacks. Koss puts a lifetime warranty on the system. Cons: They are made of plastic and the earpads are "pleather" or naugahyde, or whatever you wish to call fake leather. Not really uncomfortable, but they do get a bit warm, and for the price a nicer material could have been used. The volume control is dual, i.e., separate for left and right channels. This allows precision tweaking of the left-right balance, but it is also a pain in the rear if you just reach over to tweak the volume and you end up changing the balance because you didn't turn both the inner and outer rings the same amount. And you will change the volume a lot with these headphones, because they have a relatively narrow "sweet spot". They need to be driven a bit to hear all of their capabilities (like most quality speakers and headphones), but they do not like to be over-driven. Pro and Con: They are very revealing. This is a good thing, in that they reveal everything good about a recording and the source of the analog signal received by the amp. They also reveal everything bad about the recording and source, and since much of today's music is poorly recorded, and MP3s at low-mid bit rates make poor recordings even worse, much of the material that many of us listen to does not sound very good on these headphones. It isn't really fair to blame the headphones, but they are a bit more unforgiving than many headphones out there. If you listen exclusively to low-res MP3s of modern pop/rock, you will probably not be overly happy with the ESP-950s. But if you listen to CD's or SACDs or high quality, high-bit-rate digital recordings played through a quality DAC, you will enjoy these headphones.

It's actually not bright or strident at all. Very midrange-oriented. Very smooth. A perfect balance between not-too-dry and not-too-liquid. Just right in that quality. Extreme highs & lows are rolled off and the bass lacks kick, but it's a pleasant, forgiving, pretty even tone in between that is essentially free of artifacts in the mids and highs. Exceptionally refined and delicate. It does require very lean, detailed digital recordings & a great source to shine its best. Mine direct from Amazon, though, has a slight ground hum issue on the right channel even when no power is connected to it, though when it is connected to an audio source it's even worse. It's faint, but noticeable to me on quiet passages. It goes away completely when I touch anything metal on the unit, such as the front of the 3.5mm jack. So putting an unused 3.5mm cable in there and the other end in my waist band is a temporary solution to grounding the unit or preventing it from acting as a radio pickup. .. Or whatever it's doing. I'm not sure which is occurring on it, the non-grounding or radio pick up. Apparently, issues with the energizer/amp are common and people frequently have to send the ESP for replacement or repair. Luckily Koss has their truly perfect warranty... except for maybe the fact you have to pay for shipping both ways. For kids with perfect hearing, who are not bass-heads (or even too particular on just bass tightness, regardless of volume), and who plan on taking care of their ears (read that: keeping the volume down low and wearing musicians earplugs whenever in a loud environment), this might be the be-all, end-all of headphones. If you need a little more low-end kick & tightness or extension up top, then you may want to look elsewhere. If I'd bought this as a youth, not gotten into beat-driven electronic music, and taken care with my hearing, this would be the one.

Set comes in a very nice leather case, that holds everything and a cd player very well. Feels well made despite so light. Hooks up easy, and sounds excellent. Bass can go surprisingly low, mids clear, treble is sparkly but not harsh or sibilant. However like most high end headphones these display what music you feed in. Badly recorded tracks or using a meh source and these will not cover up or temper the sound, what goes in is fully reproduced as it is. High quality tracks fed in from a high quality source will sound heavenly. Soundstage can go 3d wide, or intimately closed in depending on the song/source/ preamp. Split volume control allows very fine tuning of the headspace. Very light on the head. These are open back. Sound and noise can come in, and everyone near you will hear what you’re listening to.

You may think this is all hyperbole, but it's not to me, This is the best deal in consumer audio IMO. You think you know your music, but until you've listened to it through electrostats, you just don't. Unbelievable detail and smoothness. Unbelievable. Battery pack. Leather carrying case. Accompanying amplifier (aka "energizer"). And a limited LIFETIME WARRANTY. Plastic build. That may turn some people off, but not me. If plastic is what makes these affordable, so be it. What matters is inside the plastic. And it keeps the weight down. As for comfort, I have never, and I mean never, worn anything this comfortable on my head. I thought the Fidelio X2s were comfortable. I thought the SHP9500s were comfortable. HD598? Nope. MDR1A? Nope. Hifiman HE400S? Nope. Try something with a light clamp and weighs next to nothing but completely engulfs your ear. I could wear these for 24 hours and not have any irritation. Some buyers report a squealing sound that requires a replacement (just pay shipping) from Koss. Mine didn't. They were perfect. But if you do, Koss will replace them until you're satisfied. I've always thought of Koss as kind of a lower grade consumer audio company. The Porta Pros punch way above their weight, obviously. But these? These have completely changed my view. Koss, I was wrong. I seriously may never buy another set of headphones again. Won't need to. Nothing will sound as good, and if something breaks, I send it back to Koss with a check for $9 of shipping. That makes me happy. UPDATE: Because I've fallen head over heels for this company, I am buying the Pro4S to have for closed back portability. I'll post a refvidw of them at some point. As for my ESP-950s? They're still amazing. I've now paired them with a Dragonfly DAC and a Little Dot MK2 tube amplifier. I could spend thousands upon thousands of dollars and not get much, if any, better than this.

2 stars is probably a bit too harsh but I have to weigh the performance and the "support" against the cost of these. I received these 4 days ago and spent several hours listening to them and comparing them to my "cheapies", a pair of 10 year old Grado SR80s. In the end, I determined that they were either defective or the amp supplied with them is not tuned to compensate for limitations in the drivers. As I mentioned, I'm comparing a brand new pair of these with my old Grado SR80's... very different headphones in design, sound and cost. I listened for about 4 hours the first night I had them and for about another 4 hours since. I'm using a Schiit Modi Uber DAC with my iTunes library... some of which is digitized from vinyl (48KHz/24bit if that matters). I have owned electrostatic loudspeakers for many years (Acoustat III's) so I'm familiar with their characteristics and sound. The Grados have been my main phones for a very long time and for good reason. At $99, they have been remarkably detailed and tonally pretty transparent. There is a bit of an emphasis in the highest frequencies but they are not harsh or bright. The low end is very solid and tight. Vocals sound a bit thin and recessed but not excessively so. When listening to Dave Grusin's "Discovered Again" direct-to-disc album, the triangles and cymbals sound crisp and clear. Switching the 950's, the first thing I notice is how prominent the mid range is. It's very full and rich but if I set the volume up to a comfortable level, the lows and highs practically vanish. It's as if the frequency response curve is dome shaped. I'm guessing this is either a characteristic of the stock amp or a defect in the amp. That's pretty unfortunate, as the headphones are quite detailed, particularly in the upper mids and lower highs. When listening to Dave Grusin's album, the triangles and cymbals are still there but are muffled and lack the presence of the Grados. I've listened to this album on many speakers too and the Grados sound more like those speakers. Switching to Elton John's 'Funeral for a Friend' was also disappointing. Early in the song, when the raspy ARP synthesizer kicks in, it sounds like someone put a pillow over it! I've never heard that on any other pair of headphones or loudspeakers. I did find a software tweak that 'fixes' the roll off at the extremes but I'm not thrilled with it. iTunes does have a built-in EQ. If I set the 16KHz slider to 6db and the 8KHz slider to 3db, that fixes the high end roll off. Likewise, if I set the 32 Hz to 6db and 64 Hz to 3db, that fixes the low end roll off. These changes actually make the phones sound damn good but I'm having trouble squaring this with my idea that everything should sound good with the tone controls FLAT. Yesterday, I called Koss directly and asked to speak someone in tech support to see if my experience was "normal" or perhaps I had a defective amp or something. The customer service lady told me I could not speak to anyone... that I had to submit a form on their website. While still on the phone, I navigated to the help page and found a live chat feature which had an option of live chat for customer service or tech support. I asked if I could use that and she said "both chat options just go to customer service. There is no live tech support chat". So, I submitted the form. I received no email confirmation of the submission and now 24 hours later, still nothing in my inbox. So... in the absence of any real help from Koss and with the nagging feeling that these are somehow 'broken', I elected to send them back for a refund. UPDATE - No reply from Koss 48 hours after submission. The "lifetime" warranty is touted in a number of online reviews for these but that's only a good selling point if you get decent service. If I do finally hear back, I'll post the results here. If I don't, I'll drop the review down to 1 star. FINAL UPDATE - I never did receive any kind of reply from Koss tech support concerning my questions. Nothing. A lifetime warranty is a great thing on principal but useless with this level of service. Downgraded this review to 1-star because of this. POST MORTEM - It's worth mentioning that even though I never received a support reply from Koss, I can confirm that they did receive my support questions... because now I'm getting marketing emails from them! LOL ***UPDATE: Sorry.. I know.. the review that never ends! I ordered another similarly priced electrostatic headphone set and that arrived today (Stax SRS-3100 system). I'm listening to those as I write this. REALLY nice... very smooth like the Koss cans but without the roll off at the extremes. Cymbals, triangles, hi-hats are crisp and clean, just the way I expect them. Bass is tight and full with just the right amount of impact. Anyway.. this is not a review for the Stax... just wanted to let you know there's a better electrostatic phone for about the same money. Unfortunately, nobody on Amazon is carrying this headphone just yet, so you'll need to do a bit of searching or wait for someone on Amazon to pick them up.

Good entry into electrostatic world but can't compare to STAX.

I owned a pair of ESP-9 s that i purchased in the 70's. I dug them out of storage but am afraid to hook them up to an amplifier. After reading about these,so many positive but wary reviews because of their supposed quirks I decided to buy cause I got an unbelievable price on new/open box. Just hooked them up last night. I have never been so satisfied with a purchase and I did have buyers remorse. I can listen to these things all day . I was up all night, started out listening to some Hi-Rez downloads then moved on to ALAC rips of some albums ,then fired up the Turntable. They sound amazing, zero distortion ,zero coloration. The bass is moving. These are an excellent addition to an already fine system,I wont bore anyone with the breakdown of my system, but again I don't care how some people can talk about the cheapness of build, there is no cheapness in sound. Buy these things, they're easily worth the sticker price, but shop around I got mine under 600. Makes me want to experiment with electrostatic speakers, maybe next year.

Comfort: one of the most comfortable headphones I used. It's very light and you barely notice its there. They won't stay on if you move around a lot. But with an energizer attached, I don't see why I would want to use for portable purposes (even with battery pack) anyways. It does get a little warm over extended period. Build Quality: the material seem cheap. The light weight, of both energizer and headphones, doesn't inspire much confidence. Most $300 dynamic headphones have better build quality. The right earpiece develop and buzz after two days of use. I am returning it to Amazon instead of using Koss customer service, which I heard honor the lifetime warranty pretty well. I will order another one and update this review based on the replacement. Sound quality: simply world class. Compared to Stax Lambda (407), Koss sounds a lot warmer and relax. But the airy, effortless, and grain-less qualities of electrostatic headphones are all there. After a lot of careful listening and comparison, you realize that Koss reveals almost (95%?) as much detail as the Stax, but with a more relaxed and musical presentation. I actually prefer the Koss sound and would listen to it a lot more than I did with Stax. The ESP-950 is great, but with a lot of room for improvement in build quality and packaging department.

These headphones are an absolute steal at the discounted price I paid for them -- Amazon special pricing on or about December 1st of this year. The sound is clear, accurate and to the point --nothing artificial about the ESP-950's. And who said that electrostatic headphones couldn't do justice to treble? Folks, let me tell you: this little monster will curl the toes off any dyed-in-the-wool treble fancier. The bass sounds are handled correctly -- not too heavy, not too harsh...just right! it's a-b-s-o-l-u-t-e-l-y gorgeous in the midranges. The soundstage is open and wide. I heard some complaints about the quality of materials used -- while it may not be Stax-metal dipped, the energizer unit and the accompanying headphones are made of sturdy plastic and-or platic composite materials that are very sturdy -- more important: it doesn't take away from the sound at all! Burn-in: Give it a solid 50 hours -- don't strain them at first and play at mid-volume. The energizer unit that comes with the stereophones is plenty powerful -- I chose, however, to piggiback them on top of an Asgard 2 headphone amp for a tiny bit more snap, crackle and pop! The ESP-950 energizer unit allows you to fine-tune the left and right-channel volume separately -- audio-customization heaven! If you're fussy about your music, you know what I mean! The unit comes with a lifetime warranty. I highly recommended it.

Luckily my pair of ESP-950 arrived problem free and after 100+ hours of burn-in, I discovered it sounded like Magnepan MMG. Good mid and overall sound for listening to soft rock ballads. Make sure it was your cup of tea if you are interested in ESP-950. While cheaply built, it was very comfortable to wear. The most immediate issue I encountered was that it was difficult to insert audiophile-grade cables into the RCA input plugs. You could read more about it from the Stereophile review. Since it was an old design headphone, I didn't try to rate it against modern headphones sound. I believed at a deeply discounted price, the ESP-950 could be a good purchase for anyone wished to add an affordable pair of electrostatic headphones to their collection and willing to get it maintained via Koss life time warranty.

This could be a long one. Two of my enduring audio memories are the first time I heard Quad ESL57s and then hearing Koss ESP-9s. Both were astonishing to me at the time, and unaffordable. I still can't afford Quad's current ESLs but when Amazon put these on for $700 Canadian, I couldn't resist. The bar on sound quality at my place has been raised a lot since those early days but these phones have not disappointed me. They are very transparent, detailed, and I have not heard any irritation or congestion on a wide variety of recordings, good and bad, old and new. Others have pointed out that they have a light balance, and that is correct, but the smoothness of the treble compensates for that. The bass seems a bit lightweight as well, but bass notes are clear, not boomy and the pitch is very well defined: the opposite of dynamic woofers. I was so impressed by the smoothness of the sound that I actually listened to test tones (pink noise), which I rarely do. Whenever I've done this with speakers (even my DSP-enabled Martin Logans) there have been obvious peaks and valleys in the response. Not so with these phones: from 40 Hz to 16k Hz, where my old ears give out, the sound level from band to band is absolutely even. Below 40 Hz, I didn't hear much, but I could feel pressure down to 26 Hz. So beware, the result of this is that you might turn the volume up too high, just because they do not irritate. On music, they do better than any transducers I have experienced on strings and choirs (to me, the most difficult of subjects)... second place in my experience goes to Magnepans, which are sweeter, more rolled-off and less transparent. They are also great on voices (whether naturally recorded or close-miked pop solos), acoustic guitar, and piano. I don't think your average metalhead would care for these at all. If you find the sound too lightweight, digital EQs are available on almost all decent media player these days: it should be easy to achieve a normal studio monitor curve, with a bit of emphasis in the upper bass and a gradual treble roll-off. No reliability issues (yet)... Comfort is great for me, although they sit very close to the ear, so you might hear some rustling noises. I have to say that Koss's marketing of these as 'portable' devices is a bit of a joke. I can't imagine packing these on a trip with a 6 AA battery pack in a leather bag the size of my old SLR camera case. But then, if I were a serious hobbyist making recordings out of the studio, I might appreciate this package. Maybe they're selling these off at these recent low prices and will come out with a sensible 'home' version of these, without the bag or battery pack and with a non-detachable headband, and maybe a bit better build quality (they are kind of cheap in look and feel, as reported by other reviewers.) But at this price, they are a real bargain.

Right Out of The Box | The initial presentation is quite nice, you're created with a genuine calf skin carry on carrying the accessories and headphones themselves. Which you have to put together since the earpieces and headband are taken off and are completely modular, completely replaceable. It's also roomy enough to fit the E90 energizer as well, in addition to having ample protective padding. The has two separate compartments that flank the main storage, which has a separator thats velcro adhere and removable so you can use it for many different things. It's very cool since I so happened to be looking for a camera bag for my DSLR and this can easily fit everything inside. Thanks Koss!! Comfort & Build Quality | The ear cups themselves have an elliptical design that are oversized, large and super comfy. Granted they are not beveled like modern headphones and your ears will rest upon a foam liner that sits between the driver assembly and the ear pads. However as someone with fairly larger ears that has trouble with my ears cramming against most driver assemblies within headphones, I found this not to be the case and it's no so shallow that this will be a problem. In fact it's incredibly roomy, so much so that I have trouble finding the right position to wear the in to optimize the seal and sound quality. Not to mention the clamping pressure is perfect, secure but not soul crushing. The headband adjustment is also smooth and well built, and in fact asides from the screws it's about the only part of the headphone that's actually metal. One downside is that instead of a perfectly smooth analogue adjustment, I prefer mechanic clicks and steps instead so you can save your preset for the most consistent fit and sound each time. Another thing is that since the ear pad and/or housing isn't beveled, behind the rear of my ears I can't seem to get a perfect seal, which of course effects bass performance. Another thing is that the headphone has only millimetres of horizontal swivel for the ear cups, unlike similar designs such as the Sennheiser HD 650, which makes the problem worse. I should also mention that asides from the left & right indicators on the headphones, there's no other way to differentiate left from right since the headphone is completely symmetrical. I personally suggest adding brail to one of the left ear cup so that in the dark it'll be easy to tell. In addition to colour coded left & right symbols. Though of course you can just wrap red and blue tape around the metal sliders I was talking about earlier. I personally just wrapped a small amount of electrical tape only on the left cable to tell which side it is from left to right. It's disheartening though that the actual headphone and amp is 90% plastic and synthetic materials which are cheap and will deteriorate very quickly. It makes you scratch your head when the bag that comes with it is better constructed then the actual headphones and amp you're paying for. Particularly the polyethylene headband and vinyl ear pads; Why not use leather for the ear pads and bags?? Obvious thought right? Poor design decision, in fact the could've saved a lot of money doing it the said way, since the surface area of the bag is much larger than the surface area of the pads and headband. My guess is they want your future business buying their OEM parts knowing full well you'll very soon need them replaced. However while the headphone is entirely plastic, it's clearly the sturdy and high quality kind and is a non issue for me. And I'm a big fan of the very open principle and design, as well as the metal grills and the rear of the headphone in addition to the felt lining behind them to prevent dust getting inside and screwing up with motor assembly. Accessories & Goodies | You're also greeted with a nice assortment of cables, such as an extension cable for the headphones, an RCA to RCA cable, and RCA to TRS 3.5mm and a TRS to TRS 3.5mm cable in addition to the power adapter of course and a nice informative manual and warranty card. What's also cool is that there is a battery powered (Type C) AC power bank that makes the E90 amp portable. For whoever in the hell would actually use a 1000$ open back electrostatic headphone in public or on the go, but nice a touch!! Thanks Koss!! If you are going to use this, I suggest buying rechargeable type C batteries which you can find right here on Amazon. The Sound | The sound at first was a little muted, a bit to polite and well 1 dimensional. However with a little burn in it opened up the sound quite a lot. Though it has a soft presentation with slightly distant presence region for vocals (2khz-7khz), it has nice bass impact and sustain and smooth if not sometimes hazy and less defined than ideal dynamics, unlike the bone conducting and lightening slam you'd get from a Hifiman HE 400i. It's a polite headphone, that has somewhat of a warm tilt. However I consider it a reference headphone since it's entire response from 20hz -10khz stays within a 10 db threshold, with no obvious or blatant peaks or dips. Making it easy to equalize for both sound professionals and consumers alike. It also has very decent bandwidth and extension, so you'll get resolved highs and well defined lows and sub bass, along with very low distortion levels and even harmonics. Since this is an electrostatic headphone it takes advantage of a completely flat and super massive diaphragm with not many acoustically disturbing and reflective parts in the way, asides from the stators themselves which achieves a very ideal AOC (Acoustic Openness Coefficient). This allows for a more planar wavefront and virtually no modal breakup since the driver is damped by air (Think about parachutes) due to the flatness of the film. It is said in the literature that the diaphragm is a 1.5 micron thick film of polyester (Their more up to date PR video says Mylar) that's coated with a proprietary material. Not to mention the entire surface area of the diaphragm is actively conducted due to the positive and negative push and pull of the electrodes within the stator, instead of circuit traces or a voice coil which allows for a more linear and pistonic motion and travel of the diaphragm instead of it breaking up into different modes. This is important because it allows for a more natural imaging experience, with sound that's evenly distributed through across the entire out ear and pinna, that utilizes the natural resonance of the out ear. Though since the headphone assembly is not beveled in any way, I found the imaging experience to lack the lazer precise, coherence and depth of the imaging of headphones such as the HE 400i & the HD800. Definitely much better than most headphones, but you don't necessarily get that out of the head experience that some others are capable of, though it's definitely no slouch!! The presence and weight of the image is indeed convincing. The best word for the sound is polite. It's polite, expansive, and has potent weight behinds it's dynamics, not to forgets it's resolving and clean sound too! Operation & Reliability | IMPORTANT DISCLAIMER* This is why the headphone ISN'T* flying off the shelves, it's mainly because this & the build quality, I'm sure you've read the Horror stories and how people have lost their very sanity from dealing with this headphone. The moment I opened and used the headphone, there was a squealing sound within the right ear cup. And an hour later no sound from the amp at all! It took a lot of troubleshooting and moving it around to different location and making sure the cables weren't near some source of noise since the unit is very very sensitive and poorly isolated from the modern modern electronics of today. A lot of guesswork, a lot of frustration of wondering what is actually causing the problem. Sometimes you ask yourself "Well is it going to work today", will it work if I plug it in via RCA or 3.5mm TRS? Off & On? Unplug everything? Another stupid design choice is that the volume pot on the energizer is wackily hard to use. Why? I mean it's just a volume control right? WRONG, it's also a flimsy channel balance control that's is incredibly inconsistent. The unit has TWO knobs and you have to independently turn BOTH of them to get the desired volume, but it's stupidly hard to achieve the perfect balance between channels. An idiotic, idiotic design choice. A simple fix that you can do that I did is simply use electrical tap to adhere the knobs together so they turn at the same time! HAHA problem solved right?? well sort of, kind of.. umm not really.. thing is the amp has this funky issues where if you turn both knobs it'll sort of work, but only for one channel sometimes. Like you have to turn it up then turn it back down a little for the second channel's volume adjustment to kick in.. I don't... it's just incredibly stupid like so many of the flaws with this headphone. This is why I think it's laughable Americans criticize China's production quality and call it cheap all the time, when American products and manufacturing are widely absolutely horrendous, much much worse than Chinese manufacturing and they're somehow proud of products from the USA, just because it's sounds more frivolous and fancy. Not to mention US labour cost is EXPENSIVE and CRAP at the same time lol. My words are going to be harsh, but it's is absolutely baffling this product has survived production for 30 years! Truly remarkable! it cost 1000$ and has materials and features that you can find since and better in a 200$ product and every single user of the headphone is at the mercy of seemingly random days of wondering the headphone and/or E90 amp will work or not!! I will go so far to say it's a SCAM!! An absolute SCAM for 1000$. To get you continuously repairing your headphones and amp and nickel and dimming you for everything in between asides from the free warranty repair, YOU will have to pay for shipping! You HAVE to be WILLING to troubleshoot or work out the quirks that will inevitably come up. I found that you shouldn't put it near or to close to any electronics especially ones that use a 60hz signals like it says in the manual. I also found that you should use your OWN cables instead of the includes one's since they don't seem to be insulated that well at all from noise and it shows since the unit is so sensitive. Though that also may be a problem since the RCA jack or so shallow that your RCA cables may not work with this thing!! AGAIN another design flaw, just make share your RCA cable terminations are the slim type , like the ones that come with the unit. And for the squealing it really could be any number of things. I find that squeezing the affected ear cup towards your head for WHATEVER reason helps get rid of it, though it may occur again out of nowhere and for what reason I HAVE NO CLUE. I also should mention that the 5 pin connector is completely proprietary so it's not compatible with other amps unless you buy a 100$ adapter. Also try to make sure you don't sweat much while using these or use these in damp/moist environments such as a sweaty hot day in Seattle, because since it's poorly isolated it could be causing some of these issues as well since it's an electrostatic. Also avoiding static electricity such as wearing the wrong sweater or rubbing your carpet with your socks may help too. This sounds silly I know, but these are the crazy and absolutely silly things you'll have to deal with and consider when buying these headphone, and for 1000$ this is unacceptable. Though of course that is decision you'll have to make, whether you're willing to deal these issues or not. Thankfully, to combat this Koss provides their famous unconditional no questions lifetime warranty. So if ALL HOPE IS LOST - Send it back to Koss and just pay for the shipping and you're covered. Addendum | TDLR* It's a polite and gentlemanly headphone with soft and plush dynamics, that has a weighty presence to it's image with sibilance and fatigue free comfort and resolving clean and even power. Making up for it's outdated design flaws and shaggy build quality. It's up to the buyer if they're willing to deal with the funky squealing, unreliable operation they'll inevitably have to deal with and troubleshoot and whether this is the quality their willing to accept for 1000$. Granted this is covered by an unconditional lifetime warranty which combats these problems, which you can send your pair to Koss's Milwaukee factory and headquarters for repair. Only buy this knowing these Catch 22's, and if you are SPECIFICALLY looking for an electrostatic headphone and energizer package like I was, since it's the cheapest bang for the buck within it's category and the only alternative to it's competitor STAX. It's an outdated headphone designed 30 years ago with many design and operational flaws. I bought it for the novelty of having a E-STAT headphone complete package around that wouldn't break the bank. But if you don't collect like I do, THERE ARE BETTER AND CHEAPER OPTIONS than the Koss ESP 950 if you don't absolutely have to have a E-STAT headphone. Just buy the HE 400i/Sundara, it's better pretty much in every way that cost HUNDREDS less and get sound on the same level, that's somewhat better. They're basically Electrostatic headphones, since their both single ended planar magnetic designs with very thin diaphragm and you pretty much get all benefits of an electrostatic headphone you can use with a normal amp. I would NEVER, EVER* buy these if this is the ONLY headphone I'll be using, can afford or have around, this is CLEARLY NOT* the best option around, best in electrostatic category & price bracket MAYBE. It's also worth mentioning I bought a used pair in very good condition sold through Amazon for 550$.. Yes 550$ it's a Total steal! - Which they are very trustworthy and reliable and only sell used pairs that customers have returned, which means at or under 30 days of use so I knew for fact I was basically getting them new. Though it's been well documented that they go on sale pretty regularly during the year and you can nab them for 6-7 hundred dollars. Try to buy these at a discounted price, otherwise it's hard to swallow due to all the said issues. I think I may keep these, we will see. If I don't find the sound satisfactory or worth having around and the manufacturing/design defects such as the godawful squealing that sound like someone is dying to disturbing I will return it. MadnewsQ

Overall the sound quality is similar to other headphones above $300, e.g. Sennheiser HD600/650, Shure SRH1540/1840 etc, while the bass and treble are both weak, which can be measured by using appropriate mics. Very light use, twice a year, 30 min ~ 60min each time. Not sure if leaving it in storage, dry and cool an clean, could bring damage to the headphone. It started to produce Whistling Noise that resembling shortwave radio tuning today and I am wondering if The noise is intermittently in one channel and quite annoying. pro: Portable and could be Battery powered cons: plastic look (fair) build quality questionable long term stability