Koss ESP950

Been comparing ESP950 vs Paradox. Pretty damn close tonally! Could almost be mistaken for a mis-positioned right channel!



Green: Paradox
Yellow: 950
measurement rig is always changing so temper the results. Disregard the plots past 10k for the most part.

Some notes:

• 950 has lighter e-stat timbre. Not Stax-y though. I wouldn't haven't listened to it until 3AM last night if it sounded like Stax plastic. Paradox is more fleshed out with better bass power nonetheless.
  
• 950 is brighter and more sibilant with instruments/vocals. Paradox shows more overall energy in treble but 8k peak (not big <5dB depending on how you position) is more noticeable to the ear
  
• Hard to say which is more resolving and plankton grabbing. Thought it would be 950 but Paradox is more refined and hi-fi to me right now Might come down to the accompanying chain.

I'm able to enjoy both immensely. Going to have a tough time going back to face tweeter.

 

Wow! These seem to match more closely than the L+R channels of some of Beyer's Teslas.

I'm surprised that the 950 maintains bass extension though - they seem to start rolling off pretty early in most other measurements. Was it difficult to get them sealed?

Also, were you running the 950 out of the E90?

 

I just stuck the 950 on a flat, felt surface. Marv tries to break the seal a bit which is probably why his measurements showed some roll-off

As addressed in the first post, running them out of a modified SRD7

 

My bad - this is what I get for not re-reading the thread. Thanks though!

 

I know I already posted with a similar question, but I really could use some input from others with the esp-950. What is the general thought on using the Valhalla 2 as a preamp before running the signal to the E90?

I quite like the effect, but am left wondering if there is some kind of technical reason I should not do this.

 

Status update: Changed out Parasound Zamp with Mjolnir (fed into SRD7). Different sound for sure.

 

With its world debut exclusively here on SBAF, make yourself a witness to the mods nobody was asking for, on a headphone that almost everyone except for those reading this thread have forgotten or never knew existed.


FYI: I'm not responsible if you mess something up, but please know that every mod should be reversible and/or not have any impact on the lifetime warranty if performed properly.


Plan

Over the past few months I have been developing the following modifications for the KOSS ESP/950 headphones.

The purpose is three fold:

• Make pads seal reliably.

• Improve the structural integrity of ear cup.

• Dampen the ear-side enclosure.



Pads

After trying some more complicated alternatives, the simplest solution became the clear method of choice. On the back of the detached pad, use an exacto knife to cut through the vinyl. Add about a 1/2 inch of foam in the shape of the stock foam insert to the pad and seal back up using electrical tape (Don't buy the cheap stuff...really, it's not worth it.)

The purpose of adding this height to the pads is that it will allow for a dependable seal onto the head and provide much better bass extension. This might be the easiest mod, but it has a great impact. I recommend buying extra pads from KOSS ($5.00 per pair direct from the manufacturer) and mutilating your spares.

Memo: I will be getting some memory foam in soon and working on the ultimate comfort version of the stock pad.

Baffle

Exploratory Surgery

If you have ever taken the pads off of your ESP/950's you will see that pretty much all of the part of the headphone ear-piece that faces your head, with the exclusion of the driver area, is made up of flat plastic. This stands out as a distinctly bad idea design if you are trying to prevent weird resonances from appearing. You might think that the cover foam is serving to dampen this baffle, however, this material is necessarily acoustically transparent as it lies between the ear and the driver.

There is normally a substance holding the thin cover foam onto the ear cup. On my headphones, the cover foam was not as tight as I would prefer, and tended to extend towards the ear just a little bit. I very quickly removed the substance holding the cover foam (it feels like a thin rubber adhesive). This reveals a set of slots in the baffle. Now we are getting somewhere! These slots had been somewhat dubiously covered by the rubbery substance that has been removed. Because a good baffle seal is VERY important, I decided after some experimentation to seal these slots with two layers of tape. See the results below.





Now the task remains of somehow improving the structural integrity of the earcup, while integrating a damping mechanism.

These two challenges were met through the implementation of a single mechanism.

By applying self-adhesive foam to the baffle plate, one could strengthen the baffle to improve isolation between backwaves and frontwaves while simultaneously providing much needed dampening for the earcup.

Using a picture of the padless earcup, I devised a perfectly scaled template for the foam piece that I needed. The foam I use, is good ole self-adhesive Creatology foam.




Once carefully cut and trimmed, the baffle-foam needs to be paired with a cover-foam piece that is slightly larger than the hole in the middle. I have opted to add dimples to my baffle-foam, because I think there might be a sonic benefit... use at your own discretion/delusion.







Now that these pieces are ready, remove the adhesive backing and stick the cover-foam onto the inside hole where the driver will be once installed. Finally, align the now complete foam unit over the earcup and firmly press to ensure the foam bonds to the flat earcup surface.

It should look like this:







Now slip the pads on and you are good to go!



Sound

It is difficult to compare the before and after since there is so much time involved in the mod, and I have no measurement gear. Subjectively, there is what I believe to be an improvement to the baffle plate dampening/isolation that adds clarity and possibly helps with imaging. When I first listened to the ESP950's I loved the fact that they have a tremendous clarity and fastness that make is seem like they are windows to where the music was performed. The baffle mods only serve to further enhance this impression.



The pad mod makes sure that the bass doesn't disappear and allows you to finally appreciate the extension that the drivers can produce. I still EQ the lowest bass up a few db, but it doesn't need near as much EQ now that the pads are sealing.



The modded headphones still very much retain the classic ESP/950 sound, but add dependable bass extension, and added clarity. Because I am the only one who has ever done these mods together, it would be easy for me to make crazy claims, but I will refrain from doing so and encourage others here to experiment with my ideas and provide any feedback they can.

 

@New Reformation Awesome work mate! I'll try to get around to implementing your mods this weekend if I have time.

 

@OJneg

Thanks! I went through a few iterations of my mods before I found the method that I posted. The more I listen the modded headphones the more I am convinced that the improvement is definitely worthwhile. More impressions to follow as I get more time to do critical listening.

If you have any questions about the mod just let me know! It would be amazing to eventually have some graph info for the modded vs stock ESP/950's.


Oh, I also had a try at a purely aesthetic mod for the E/90 amp. You might not be able to see in the pic, but the finish is brushed metal.



I think it looks a whole lot sharper next to my other gear than it did before.

 

Update: I have acquired some memory foam and incorporated it into the pads on the ESP/950. Though the mechanics of the pad mod are super simple, it is so difficult to get everything back together that some will probably want to give up.

•Simply use a sharp exact knife to cut through the back of the pad on the vinyl area closer to the outside edge.
•Flip the lip that attaches to the headphones over so that you have good access to the area where the pad has been cut.
•Take out the stock foam.
•Using the stock foam as a template, cut your memory foam into the proper shape.
•Stuff the memory foam in first, then push the stock foam in behind it. (The memory foam I have compresses quite a bit and needs some support to function 100%.)
•Use electrical tape to seal the seam back up. This is VERY tedious work and requires a lot of patience to get right.
•Put the pads back on the headphones.

Verdict? The pads are now SUPER comfy and offer practically perfect seal. The sound is better than ever and that bass is slammin' pretty nice for an stat! The sum total of my mods is a headphone that offers incredible clarity and transparency while avoiding the pitfalls of stridency, hollowness or plasticky timbre. To the contrary the sound sig is nice and dynamic with deep bass and no shoutyness through the mids or lower treble. These headphones have come a fair way since I bought them and I think they might be endgame for me.

 

I do this same thing but with a Lyr 2 into a Mjolnir ExStata that drives the Koss'. This seems to give the effect of a little more dynamic sound, plus some additional flavor from the tubes. The ExStata has a passive volume control and I run it wide open, using the LYR 2 volume knob. I haven't tried it with the E/90, but it could be a little noisier depending on the quality of the E/90 volume pots and circuitry. Just a guess, but it may not even be a concern. I don't see any harm in doing this if you like the sound.

 

Out of nowhere, a wild Steve Guttenberg review appears!

http://www.cnet.com/news/the-koss-esp-950-headphone-dazzles-the-audiophiliac/

It is super weird that he would give a review now with the ESP/950 being as old a headphone as it is, but he gives them high praise. He also compares them to the Stax SR-207 and LCD2 if anyone is interested.

@OJneg
Did you ever get a chance to attempt the mods I have posted? I know life gets busy, so its fine if you haven't, but I was interested in gaining your more seasoned expertise on the effects of the mods. I'm still loving these headphones post-mod.

 

Haven't posted a mod here in a while. I have recently worked on making full-blown memory foam pads that compensate for the need for greater thickness along the bottom, and thinner thickness along the top edge. It's amazing how much sub-bass and dynamics depend on a perfect seal. Listening to the first working model of these re-mastered pads, and things are rocking hard. On a whim I also conditioned the ear-pad material a bit to make it softer and less crinkle-sounding. If there is any interest I can post pics/instructions.

 

That would be great. If you can post pics of the area you taped, that would be good too.

 

I was thinking of having custom leather pads fro the 950 made by these guys:

http://vesperaudio.com/earpads

Would be about $50, which isn't too bad. I'm really intrigued by thought of pads that are more comfortable, and provide a better seal (to get better bass). I would love to see pics of the modded pads!

 

Any particular things to look out for in a used pair?

 

Noise in the headband and the cups. I can lightly twist my headband and it sounds like crinkling paper. I will be sending them for repair. Also, sometimes their is a squeal, but I haven't experienced it.

 

Just got one used for cheap, some impressions after around 2 days (w/ stock amp)

• Sounded rather boring and unimpressive at first, does not really have much "wow" factor like some other phones, think watching a live concert from home with a nice loudspeaker system piping live music versus standing front row at the same live concert.
• Seems to be a very even FR without significant peaks or dips, HE-400i's and TH-X00s sounded rather aggressive and relatively fatiguing in comparison, great for extended listening sessions, pretty resolving as well
• Very smooth and non-sibilant mids and highs, compared to the two phones above, downside being that it can be rather lacking in impact and weight, which is not good for genres which like more "bite", also seems to be slightly dark-ish in tone, coming from the ESP's, TH-X00's feels like someone strapped subwoofers to your head, for better or worse.
• Bass has decent extension, but lacks impact and reverb, this may be a seal issue.
• Very wide imaging L-R, with good separation in those directions, not sure otherwise.
• Very light and comfortable, even if pads are very meh

Overall, pretty impressed with these for the price, likely going to be keeping them for quite a while..

 

I appreciate those who are interested in my continuing mods making their enthusiasm known. I finally had the chance to rework the pads a bit more and to simplify the vertical tilt that facilitates a better seal on the bottom edge of the earpad. Throughout the process of developing mods, I have learned that simple is best. I tried some more complicated methods than I am posting here, and the more simplistic fix is better because it is more stable physically and sonically. I only have a phone to take pictures with at the moment, so bear in mind the camera work is not my best.

Because the pads are SO hard to tape back up once you stuff the memory foam inside, I will be posting a picture of the re-sealed pad along-side the foam that comprised the stock padding. I have TWO pieces of memory foam the thickness of the stock foam pressed inside the cover of the earpad so you can easily imagine that it is a tight fit. Everything is stiff soft, when placed on the ears though.



Use a very sharp pen-knife to make a cut about 1/4 inch from the outside edge of the pad. Hopefully you can see the general methodology of opening and resealing (using electrical tape) the pads by looking at the picture below:




The necessary additional thickness needed to correct the stock pad's problem with sealing along the bottom is remedied by cutting a second piece of foam and attaching that on top of the foam already applied to the ESP/950 chassis by means of double sided tape. You could use the adhesive on the back of the foam, but I wanted to leave the option for easy removal.



After the pads are put back on there is pretty much no visual difference from stock:



SOUND IMPRESSIONS:

It seals better, so the bass is nice and reliably present. The memory foam is less prone to making noise and increases the wearing comfort even higher than before... Which is saying something. As an unforeseen consequence, I think that adding even more mass to the main baffle has tightened the sounds even more. At this point I can see maybe investing in custom leather pads out of an interest in having a nice aftermarket add-on, but I'm not sure that there would be any functional addition beyond the mods I have already made.

The Koss electrostats that were originally introduced the same year I was born are still VERY competitive over two decades later. I found a picture of an old review from when they were first introduced and amazingly they were priced at $2000.00. When adjusted for inflation, they would have been introduced at about $3500.00 new in 2016! Audio gear is not good because it is expensive, but let's not forget that the ESP/950 was once VERY high-end gear that retailed for top-dollar. Today, the quality of the gear remains the same, but it is far more accessible than it once was.

 

Good Stuff, I would try it on mine if I wasn't so bad at DIY...

On a sidenote, where do you get these craft materials (memory foam + creatology stuff) for decent/cheap prices?