This is review and detailed measurements of Drop's X KOSS ESP/95X electrostatic headphone. It is on kind loan from a member and when it was available, cost US $500. Not sure what is different with it from the original KOSS model which I think cost $1000.
Typical of most electrostatic headphones, there is a required amplifier/driver ("energizer"):
The headband separates from the earphones using a clever and simple button on each side. The rest is not so impressive as the plastic is what $10 toys would be made out of. Same applies to the amplifier which looks metal in the picture, but is very cheaply made plastic. The plastic has one advantage: the headphones are super light. Wearing them was comfortable for the 2 hours or so that I used them for testing.
The headband friction fit is too loose so the position of the headphones does not stay the same. Pull them on and off and they change.
The retainers on each side of the earphones creeks as you move around.
The most major flaw is the volume control. They copied the one from Stax where you have the left and right volume on the same shaft. On Stax, you adjust the two but then when you turn the very large knob, both channels adjust at the same time. Not so here. It is darn near impossibly to adjust the volume and not have one channel change more than the other. It was so frustrating that that I gave up on using it and set it to near max and used my DAC's volume control.
Massdrop X KOSS ESP/95X Measurements
I measured ESP/95X on GRAS 45CA standardized headphone measurement gear which is (still) on loan from the company. The drive and analysis was the Audio Precision APx555. Let's start with our new dashboard:
Distortion is quite low for low frequency source tone of 40 Hz (peak amplitude in sampling of music). We can see second harmonic at 80 Hz to the tune of -65 dB which is quite good.
Most important measurement though is frequency response:
The dashed blue line is most preferred frequency response for a headphone. Between 200 and 3 kHz, we have decent agreement. Below that we have significant deficiency which is the case with many headphones. We do have drooping in lower treble as indicated by the cursor lines near 5 kHz. There is also some extra energy around 1 kHz. Lack of bass and highs would indicate a sound that would be rather flat and unexciting.
While I have become comfortable with the above comparison of measurement versus expected, some people may want to see the two substracted from each other and look at the deviation. A flat line here then indicates 100% compliance with the preference curve:
This looks a lot worse than many other measurements out there. The reason is that I use 20 dB span and others use many multiples of this. Increase the range vertically enough and you can make any frequency response look flat!
Anyway, we see the shortfall in bass from 200 Hz down. There is that strange shelving which may be some kind of electronic filtering in the amplifier.
As usual, ignore stuff at or above 10 kHz.
Somehow I lost my IMD vs level test from the last review.
Until I recreate it, let me treat you to other distortion graphs:
For some reason this AP graph only shows second and third harmonic. Note that this is pure THD and has no noise in it.
Comparison to Stax SR-303 Headphones
I thought it would be good to perform a quick comparison to one of my Stax headphones, the SR-303 driven by their lower end SR-313 amplifier:
This response has a much better adherence to our preference curve. We have matching bass down to 50 Hz compared to 200 Hz in ESP/95X. And then slopes down gradually, kind of like a speaker would. This looks like some kind of high pass filter.
Massdrop X KOSS ESP/95X Listening Tests
Out of the box the sound was decent. I think having that first peak in the 3 kHz help to not have a hollow sound. That said, lack of bass is obvious, and there is little sparkle. I heard no "speed" people talk about. Once again I think people take the lack of bass and equate that with 'speed." The large earphones do provide a taller presentation which as a fun exercise, you can adjust up and down as you move the cups.
I decided to use EQ to improve things and this was more time consuming than I expected. Here is where I landed:
I had to build a custom bass boost for it as you see above. It responded very well to this.
There was some extra energy around 1 kHz. I went back and forth on this a fair bit but at the end, I decided to take it out using that teal Band 1 filter.
This last bit was the most complicated. I tried to boost what was missing around 5 kHz, but not let the overshoot at 6 kHz make it too bright. I think a more proper automatic filter generation may work better here than my eyeballing it.
When it was all said and done, the ESP 95/X went from rather unexciting and dull to a "hifi speaker." We now had bass, more highs and less midrange emphasis. Indeed I enjoyed it for a couple of hours listening to a lot of music.
Then out of the corner of my eye I saw my Stax SR-303 and decided to listen to that. The tonality of the Stax out of the box was way more pleasant than the ESP/95X. The Stax material was also in a completely different class. This prompted me to then measure the Stax as you saw in the previous section, confirming what I was hearing.
There was a difference though: the ESP/95X could barely get loud enough for my music selection. The Stax misses that mark. Turn it up beyond a certain spot and the drivers start to crackle.
Conclusions
I don't know why people are so fascinated with how some speaker/headphone is made. What matters are the results. If full frequency response is not delivered faithfully, I don't care if you bring a live orchestra to my room. I won't like it. We have that problem here to some extent. The frequency response deficiencies are there and are significant but are not show stoppers. Correction is mandatory unless you want something plain sounding with little dynamics, bass and sparkle in the highs.
The ESP95/X didn't light up any magic for me that people talk about other than what the large size of the driver brings.
If you are itching to hear what electrostatic headphones are about, you can opt opt for these and I won't chase you out of town. Otherwise, I suggest looking for a headphone with better response. So while I can't recommend the Massdrop X KOSS ESP/95X, I am not opposed to them either in a sea of other headphones, many of which are worse than it.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any kind donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Typical of most electrostatic headphones, there is a required amplifier/driver ("energizer"):
The headband separates from the earphones using a clever and simple button on each side. The rest is not so impressive as the plastic is what $10 toys would be made out of. Same applies to the amplifier which looks metal in the picture, but is very cheaply made plastic. The plastic has one advantage: the headphones are super light. Wearing them was comfortable for the 2 hours or so that I used them for testing.
The headband friction fit is too loose so the position of the headphones does not stay the same. Pull them on and off and they change.
The retainers on each side of the earphones creeks as you move around.
The most major flaw is the volume control. They copied the one from Stax where you have the left and right volume on the same shaft. On Stax, you adjust the two but then when you turn the very large knob, both channels adjust at the same time. Not so here. It is darn near impossibly to adjust the volume and not have one channel change more than the other. It was so frustrating that that I gave up on using it and set it to near max and used my DAC's volume control.
Massdrop X KOSS ESP/95X Measurements
I measured ESP/95X on GRAS 45CA standardized headphone measurement gear which is (still) on loan from the company. The drive and analysis was the Audio Precision APx555. Let's start with our new dashboard:
Distortion is quite low for low frequency source tone of 40 Hz (peak amplitude in sampling of music). We can see second harmonic at 80 Hz to the tune of -65 dB which is quite good.
Most important measurement though is frequency response:
The dashed blue line is most preferred frequency response for a headphone. Between 200 and 3 kHz, we have decent agreement. Below that we have significant deficiency which is the case with many headphones. We do have drooping in lower treble as indicated by the cursor lines near 5 kHz. There is also some extra energy around 1 kHz. Lack of bass and highs would indicate a sound that would be rather flat and unexciting.
While I have become comfortable with the above comparison of measurement versus expected, some people may want to see the two substracted from each other and look at the deviation. A flat line here then indicates 100% compliance with the preference curve:
This looks a lot worse than many other measurements out there. The reason is that I use 20 dB span and others use many multiples of this. Increase the range vertically enough and you can make any frequency response look flat!
Anyway, we see the shortfall in bass from 200 Hz down. There is that strange shelving which may be some kind of electronic filtering in the amplifier.
As usual, ignore stuff at or above 10 kHz.
Somehow I lost my IMD vs level test from the last review.
Until I recreate it, let me treat you to other distortion graphs:For some reason this AP graph only shows second and third harmonic. Note that this is pure THD and has no noise in it.
Comparison to Stax SR-303 Headphones
I thought it would be good to perform a quick comparison to one of my Stax headphones, the SR-303 driven by their lower end SR-313 amplifier:
This response has a much better adherence to our preference curve. We have matching bass down to 50 Hz compared to 200 Hz in ESP/95X. And then slopes down gradually, kind of like a speaker would. This looks like some kind of high pass filter.
Massdrop X KOSS ESP/95X Listening Tests
Out of the box the sound was decent. I think having that first peak in the 3 kHz help to not have a hollow sound. That said, lack of bass is obvious, and there is little sparkle. I heard no "speed" people talk about. Once again I think people take the lack of bass and equate that with 'speed." The large earphones do provide a taller presentation which as a fun exercise, you can adjust up and down as you move the cups.
I decided to use EQ to improve things and this was more time consuming than I expected. Here is where I landed:
I had to build a custom bass boost for it as you see above. It responded very well to this.
There was some extra energy around 1 kHz. I went back and forth on this a fair bit but at the end, I decided to take it out using that teal Band 1 filter.
This last bit was the most complicated. I tried to boost what was missing around 5 kHz, but not let the overshoot at 6 kHz make it too bright. I think a more proper automatic filter generation may work better here than my eyeballing it.
When it was all said and done, the ESP 95/X went from rather unexciting and dull to a "hifi speaker." We now had bass, more highs and less midrange emphasis. Indeed I enjoyed it for a couple of hours listening to a lot of music.
Then out of the corner of my eye I saw my Stax SR-303 and decided to listen to that. The tonality of the Stax out of the box was way more pleasant than the ESP/95X. The Stax material was also in a completely different class. This prompted me to then measure the Stax as you saw in the previous section, confirming what I was hearing.
There was a difference though: the ESP/95X could barely get loud enough for my music selection. The Stax misses that mark. Turn it up beyond a certain spot and the drivers start to crackle.
Conclusions
I don't know why people are so fascinated with how some speaker/headphone is made. What matters are the results. If full frequency response is not delivered faithfully, I don't care if you bring a live orchestra to my room. I won't like it. We have that problem here to some extent. The frequency response deficiencies are there and are significant but are not show stoppers. Correction is mandatory unless you want something plain sounding with little dynamics, bass and sparkle in the highs.
The ESP95/X didn't light up any magic for me that people talk about other than what the large size of the driver brings.
If you are itching to hear what electrostatic headphones are about, you can opt opt for these and I won't chase you out of town. Otherwise, I suggest looking for a headphone with better response. So while I can't recommend the Massdrop X KOSS ESP/95X, I am not opposed to them either in a sea of other headphones, many of which are worse than it.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any kind donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
