Thanks to r/headphonelibrary for supplying this tour unit.
@Mshenay is the one who runs it so thank you for having this tour avaliable which recently started again in January 2021.
Accessories
The Koss ESP 95x comes with an e/90x energizer and AC Adapter, 3ft RCA to RCA cable, 2ft 3.5mm to 3.5mm cable and 6ft extension cable.
Fit and Comfort
Comfort wise, I say these are probably the most comfortable headphones I ever tried. It just feels so light on the top headband and does not create any hot spots. The clamp force is a bit light though which I do not mind but at the same time it falls off my head if I am not in an upright position. The pads have a stiffer foam material but not to the point where it could cause comfort issues.
Build
The build for the most part is pretty much plastic from what I can tell besides the part that controls the headband’s extension. It really reminds me of Stax ear speakers I used to own but the build quality on the Koss I would say is better and more held together. I do not have much of an issue with this as you do get a light, comfortable headphone which I can not say many other headphones are anywhere near as comfortable. I do like that you can easily take this apart and replace the headband if needed. The energizer itself is pretty compact as well being about 6”x4.5”x3” and feels light. Also seems to just be plastic and the knob does have an option to change the volume from the left channel and right channel. I think this can be useful as electro stats can sometimes have one side going quieter over time when not properly taken care of.
I also did not notice any creaking noise while I did use this. So that was not really much of an issue for me.
Sound Leakage:
Tried to volume match to what my other headphones I have, and I would say the sound leakage is above average in terms of how much everyone can hear around you. Something like an HD 6xx series or HD 800 would leak less than this, but it is not as bad as a Stax lambda or Ananda.
The sound:
I guess if I were to summarize the sound, I would say recessed sub-bass, recessed lower mids, slightly shouty upper mids, but warm on the treble.
Sources:
I ended up using SDAC-Balanced ->E/90x energizer on foobar2000 with flac files.
Bass
So, this follows a similar feeling in the sub-bass to what most electro stats sound like. I tried some sub-bass tests such as A1 2019, and massive attack angel, and for the most part the sub-bass sections were whisper quiet and there was not much of sense of rumble. I tried to EQ in sub-bass and happy to say it does EQ well, but the amount of EQ it needs for my taste is a bit more than I would be comfortable using. I would say in the +10db range to somewhat get a sense of rumble in these songs and towards my preference. The mid-bass to upper bass has a bit more body in comparison but I still sort of find it a bit recessed. The decay on the bass is fast as well. Overall, really what you expect out of an electro stat but maybe a bit better than Stax’s offerings in this range.
Mids
The mids on the other hand seem a bit more balanced than the other Stax products in this price range. The lower mids do seem a bit recessed where I would be EQing in a few db in to give it more body, usually I prefer more emphasized lower mids. The other part is that the upper mids can be a bit shouty but not anywhere near as bad as stax lambdas can be. I find the part to be well done by Koss versus Stax’s lambdas as they maintained a somewhat inoffensive and relatively balanced signature. I did not really need to tweak the upper mids too much versus but a few db down on 1.5k were nice to have.
Treble
So, I believe my favorite part of this headphone would be the treble as it can be mostly warm and easy to listen to. The treble is pretty much warm throughout it all. I did have an L700 and it just sounded so bright in comparison, the ESP 95x really makes it a lot nicer to listen to. I did notice that were some peaks on 9k, 11k and 13k and made it sound just a bit airier than what I am normally used to. Although to me it does not feel extreme, I just lowered those parts by a bit.
Dynamics:
So, like most electro stats I heard, the macro dynamics are just really compressed sounding, especially in the bass. I would say these are about as compressed as the L700 I had. If macro dynamics are important to you, I would avoid these. It might also not be helping the amount of sub-bass presence this headphone has as I did have to overcompensate to get rumble and better extension.
Detail
Detail wise, I feel these are just about right for their price point. At the time of writing this review, they are on sale for $390 on Drop, although already out of stock for anyone with 120V. I find them a decent offering in this aspect. Just comparing it to my HD 650 which is about $220 if you Drops version, it is getting out resolved by the 95x. Although it is not a groundbreaking amount of more detail you are getting with the 95x. It sounds about right for the price difference.
Separation
Separation wise, it is pretty good as the HD 650 seems to be suffering in this regard in comparison. The 95x easily comes out on top in terms of separating instruments and making it seem less congested in busier songs. From memory, I believe the amount of separation is closer to an Elex but I am not completely sure as it has been a year since I listened to those.
Soundstage and imaging
I would say the soundstage is a bit above average, being bigger than the HD 650 easily, and being a bit bigger than the elex was. Imaging wise, I feel it is pretty well on the left right and back sides, but the front image is a bit hazy feeling. But it is somewhat there just not as defined as it could be.
Comparisons:
Sennheiser HD 650:
Both seem to share a bit more of a warmer signature, with the Koss seeming to have a bit more energy in the upper treble and less energy in the bass. I can see the 95x being an upgrade in terms of separation, soundstage, imaging, and detail retrieval. Although I believe the 650 still does macro dynamics better. The Koss is more suited to some one not really relying on dynamics or intense amounts of bass. The 650 is a good bit nicer with its timbre though.
Focal Elex:
Memory is a bit hazy on this one. But I do remember the macro dynamics being exceedingly well for the price and blowing out the 95x in this aspect. Detail retrieval wise, I feel the elex might be a tinge better but it is not a groundbreaking amount, mostly just in the amount of clarity the Elex has over the 95x. Soundstage wise the 95x is better, and comfort in my opinion is better on the Koss as well. I do find the elex to be a bit more offensive in the upper treble though and shout over the Koss though.
Would I buy it?
I think the Koss ESP 95x is great system for anyone interested in getting in the electrostat sphere. For the price I would easily take this over the L300 + 252s but if you do value detail and only that, I would consider the L300 instead. The 95x is so much nicer tuned than the lambdas Stax has currently on offer, that makes ms turn to the Koss instead. Stax’s lambda series can be offensive in the shout and the treble can be leaning towards the bright side.
It scales very well for much less than other headphones at the same price point through the same equipment. I chose the Mjolnir amp because birgir sells very well made equipment for nothing more than what it cost him in parts and he designed it to pair well with the SR 007. That doesn't mean you can't use a cheaper Stax amp and come away with a very pleasant and competent system. I haven't tested Stax cans or amps yet so I can't vouch for that combo. At $1850 it's not a bargain but you'd be paying a lot more for an L500 or L700 with the same amp.