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Koss UR-55 Soundstage and Grill MOD

post #1 of 41
Thread Starter 

UR55-mod [1024x768].jpg


I'm not aware of many people owning the Koss UR-55, but I just did a mod the other day and I liked it so much that I felt I absolutely MUST share it with everyone. It turns a good headphone into something really great and improves many things.

I always liked the UR-55 but sometimes I felt the sound was very very slightly muffled, but still very good for the price. The sound was just not as crystal clear as my Maxell DHP-II or even the Beyer Dynamic DT-235. They do have more bass than both and are even more fun to listen to. They seem to have the Porta Pro sound signature in a way. I don't think it uses the same driver at all. The UR-55 driver appears to be 40mm. I don't think it's a titanium driver, because the sound is not as bright as the KSC75 to my ears. The highs are definitely rolled off and the sound signature is very non fatiguing.

Since my UR-55 wasn't being used as much I decided to try and open them up to experiment. I also wanted to figure out if they were really open, closed or semi-open.

The pads along the edges are held in place by adhesive behind some plastic. The adhesive of course doesn't cover up any holes. What you do is put a small thin flat screwdriver behind the plastic and gently lift up and work your way around. Once it's removed there is now three screws. I 100% suggest to DO NOT REMOVE the ear pads. If you do, be very, very careful. I was able to reuse mine after removal.

Once the screws are removed you will notice that the metal grill has thin fabric covering the back of it. The grill is held in place by bent small metal tabs. To remove the grill you can bend the tabs and press gently against the grill with screwdriver. I had to go back around to the outside and pry off the grill. Once it's off, there is very little chance it's going to be reusable!

Next, remove the fabric from the plastic. This takes a long time since it's glued in place in four areas. The fibers hold on and it's hard to get them off.

If you are going to remove the metal grill I suggest doing it WITHOUT removing the pads. This may be  very difficult and I haven't tried it. You can pop off the Koss logo and use the hole to force it off. Just be careful to not poke the driver inside!!

When I played music from them after doing this mod the sound was quite impressive. The differences to my ears were not subtle. Have you ever done the Grado SR-60/80 mod? The result of doing this is even MORE noticeable.

I have a feeling that the driver of the UR-55 is similar to the driver of the SR-80 and needs air to sound it's best. I'm not sure of this, but I think this is the case.

The biggest change i've noticed is that the soundstage is much better and more noticeable. The overall sound is much more clear and I'm not sure how this could be. The highs are obviously still rolled off, but the mids SEEM to be even more forward. The bass seems to be reduced slightly, but not as bloated as it was previously in some bass heavy songs. Imaging is just amazing for a $50 headphone. Now this part is probably just my imagination, but it felt like there was even more detail than before. In one song, I even heard some recording hiss.

I did this mod at 3am and I was so impressed with the differences that I laid in my bed listening to all my music until 5:30am! No joke!! Despite the driver being a bit more open the sound doesn't leak out as much as my Grado SR-80 with the grill removed. It's strange that there is still some decent isolation.

I thought that maybe all these changes are my imagination, but I definitely don't think this is the case. I listened to them for another 3 hours today and i'm still impressed. This may also be a good budget solution for a portable open gaming headphone. I'm going to test them out later today.

Hopefully someone who likes doing mods and doesn't mind some risk can try this. The mods are 100% NOT reversible, so it is a risk and you most likely void the warranty! If you don't like the changes, you've wasted $50. I felt it was totally worth it in every way. It reminded me of when I did my Grado SR-80 mod. It felt like I had turned my $80 headphone into something much more expensive. I can't say it will be the same way with this, but the sound was really improved by a lot.

 I've noticed that some low quality MP3s I have sound VERY bad on these. Even more so than a lot of my other headphones. They're not THAT revealing, but I kept wondering why some music sounded like garbage on these and it was my source file.

The best music for these that I have is Pearl Jam, Radiohead and Imogen Heap. If Imogen Heap doesn't "Wow" you on these headphones after the mod, I don't know if any under $75 headphone will. After lots of testing I don't think these need an amp, but do benefit from one.

Edited by tdockweiler - 11/20/10 at 2:06pm
post #2 of 41
Thread Starter 

I didn't really expect many replies to this thread due to lack of interest right now in the UR-55, but that's OK!

Today i've acquired my old un-modded pair of UR-55s. Originally I bought them but gave them to my mom when I upgraded to my DJ100. Since I became interested in the UR-55 again I just bought a new pair. It turns out she never used them much and would have just given me them back! She just preferred the Shure SRH-240 due to better isolation when she's on her treadmill.


So now I have an un-modded UR-55 and the modded version.


The UR-55 modded is now one amazing headphone for $50. It blows the Porta Pro away in nearly every way when modded. I think it could easily compete with a few $100 headphones.



I've compared the two today for nearly three hours while watching basketball while it's muted in the background. Again, the differences are HUGE.


1) Soundstage is improved

2) Bass is less bloated and better controlled

3) Detail has increased by a lot

4) Mids are now much more forward and less drowned out during bass heavy songs


If you compared the two side by side yourself seriously you'd be shocked at the differences.


WITH the grill the sound is muffled a bit. It's not so noticeable in some songs, but in others it is. This is definitely 100% caused by a combination of the grill and fabric cover. Once removed the sound is pretty much crystal clear. The bass is reduced SLIGHTLY, but trust me, it's totally worth it. I felt that before the bass was way too excessive in some songs and it took away from the music.


More people really need to try this headphone and mod it! I think it can compete with my SR-80. I should compare them next. UR-55 is only $50!


Here are a few notes I took. You can skip them if you want since it's nearly the same result from each song:




One Republic - All the Right Moves


WOW! The difference between the two is SUPER HUGE! The sound is very muffled in comparison. It almost feels as if a thin cloth is being covered over the driver. Cymbals and drums are slightly more distant sounding and not as easy to hear. Even vocals sound a bit muffled.  It almost feels as if the bass drowns out the mids a bit. You can actually feel as if the bass is vibrating the plastic shell and degrading the sound quality, however that's possible.


Sorry to sound cheesy, but it feels as if a veil was lifted kind of. More detail is revealed and the hard to hear sound of the cymbals is easier to notice. The overall sound is soooo much more clear.

Pearl Jam - Rival


The only noticeable difference is that the modded version has less bass. At times I felt like the bass kind of intrudes into the mids a bit. The sound un-modded is again a lot less clear.


You can hear a dog at the beginning and it sounds as if he's playing tug of war with a dog toy against a person. You can hear him growling and moving around in different positions in the headphones. In the background you can hear the wind is really loud. You can even hear the sounds of the dog's feet on the ground, almost as if a twig or something has snapped. Could have felt there was a crackle of a fire somewhere there, but probably not.

Pearl Jam - Why Go (TEN)


Vocals and mids sound very recessed and distant. One of the very few Pearl Jam songs that sounds bad on the UR-55. Sounds almost like this song was recorded in a cave. You can even hear sound bouncing off walls.


I think this song is supposed to sound like this. There is a lot of echos in this song. It's slightly more clear now and less cave-like.

Nine Inch Nails - Ringfinger


Can't get over how muffled the sound is on specific tracks compared to the modded version. The grill and fabric is definitely the reason why some songs sound muffled. I don't know why!

During this song at the start you can hear a very light static like sound in the background that repeats every few seconds. On this version you can barely hear it.


That static sound is so clear now.

Chara - Let Me Know


Severely bloated bass during this song. This is not supposed to be how this song sounds. You can even feel the cups vibrate.


Bass is now more accurate.

Utada Hikaru - Fight the Blues

This is a great song for headphones for some reason. The only difference is that un-modded, it sounded much more muffled, even more so than many other songs. On the modded version the entire song is crystal clear.

Radiohead - 15 Steps

Another one of those songs that gets ruined on these headphones when un-modded due to the bloated bass. It seems to drown out the mids a bit. Vocals are also a bit harder to hear.

Vocals on the modded version are very forward and clear. Bass is now more accurate and natural.

Nine Inch Nails - Sin

I've listened to this song a million times in my car. Sounds PERFECT on the modded UR-55. The room this was recorded in seems to have a lot of echo.

Eddie Vedder, Into the Wild Soundtrack - Rise


Perhaps one of the worst sounding songs for the un-modded UR-55. It just seems to try to be constantly annoying. Everything sounds like a cloth is being put over the driver and vocals are distant.


Slightly better here, but I don't find this a fun song to listen to on this headphone. I don't know why.

Chara - Duca

When listening to the un-modded version her acoustic guitar sounds a bit un-natural. Again, the sound is crystal clear on the modded version.



post #3 of 41

If I understood what you did right (I just read through it quickly) you basically turned these into an open headphone from a semi-open, that would explain all the differences you noticed.


Since most mods usually involve removing something from the headphone, I have to wonder if just having a driver held up by nothing but the headband and maybe a plastic circle around it (kind of like if you took the grille and inner foam off of a HD600/650) would be the best design for most headphones.  Zero resonance, zero damping, just straight driver -> ear.

post #4 of 41
Thread Starter 

Yeah these are listed on the Koss website as being open. I'd really call them semi-open, but barely since the fabric and grill kept air from getting in there it seems like. Somehow the bass and the grill/fabric were just not a good combination and messed with the sound signature a bit and made the bass a bit too much with some songs. I bet just removing the fabric would have been enough, but it's too hard to remove just the fabric and keep the metal grill.


I guess with this headphone it would be like the difference between a closed Grado SR-80 and an open one. I bet the closed or semi-open would sound NOWHERE near as good. I've never tried that though.


I wonder if putting felt around the edge of the UR-55 and on the back of the driver would do anything. Maybe. The sound is already good enough as it is.


I guess some drivers sound best when closed off a bit. I tried to remove the foam on my DHP-II Maxell to make them more open and the bass and sound just got much, much worse. So bad that I immediately reversed it.


When modding my SR-80 I also removed the grill and button and that helped the sound slightly too and i'm not sure why. Since it was already mostly open anyway, it was very subtle.


BTW I think the driver enclosure can change the sound a lot. My DHP-II kind of has a hollow sound to it. Not as bad as it sounds really. I bet if it was in a different type of ear cup it'd sound very different. This is obvious though, but it depends on the type of driver I guess.

post #5 of 41
Thread Starter 

I've been comparing the fully modded SR-80 with the modded UR-55 side by side for the last two hours. I was going to do a review, but the differences are so minor that it's not worth it.


So far i've found these differences:


1) The modded SR-80 has more bass impact. The SR-80 mod also added far more mid-bass. Bass heavy songs are better on the SR-80 slightly.

2) Vocals on the UR-55 are far more forward.

3) Soundstage and Imaging is far better on the UR-55

4) This is obvious, but the SR-80 has less rolled off highs and is much brighter.

5) Believe it or not, mids are slightly more forward on the modded UR-55, but at the same time very slightly less clear. Maybe just 2-3% more clear on the SR-80!

6) Some background detail is more noticeable on the UR-55. Recording hiss is much more present on the UR-55.

7) Metal would be far better on the SR-80 I imagine.


Basically if I wrote down all the strengths and weaknesses it'd come out to a tie. Un-modded the UR-55 would lose...badly.


For sound quality from best to worst, here is how I'd rank my portable headphones under $80:


1) Modded SR-80 (8.5) / Modded UR-55 (8.5)

2) Maxell DHP-II (8)

3) Beyer Dynamic DT-235 (7.5)

4) Audio Technica ATH-M30 (6.5)

5) Sennheiser HD-497 (6)


Without the mods, the DHP-II would rank higher than the UR-55 easily.


Modded UR-55 or the DHP-II would be a perfect budget headphone for gaming. I've tried them, but my favorite still is the Koss Pro DJ100 at any price and prefer it over my k601 for gaming! I bet it'd hold up well against the AD700! For music and games the DJ100 would get a 9 for sound from me, but it's not really portable and needs an amp. BTW an un-modded SR-80 I'd give a 7.5/10.

post #6 of 41

Holy crap you put a lot of work in this lol... Hopefully if anyone has a ur-55 they end up reading this, it sounds like its a pretty big improvement.


Also, you have way too many low end phones smily_headphones1.gif

post #7 of 41
Thread Starter 

Yeah it's that darn headphone addiction. I was just so amazed with the differences I had to know for sure if it all just wasn't my imagination. Totally 100% NOT my imagination. I'm even willing to say they improve the sound by like 50%. Nowhere near subtle.


I'd be surprised if anyone read all that I posted. I really hope someone might be willing to try out this mod. The UR-55 deserves some attention. It's just an amazing headphone when modded. It's now extremely detailed. Since when do you have a $50 headphone where 128kbps MP3s sound like garbage and on some songs you can here what appears to be recording hiss! The level of detail is so high for such a cheap headphone. They still also have that fun sound signature.


Today I did some more experimenting with the UR-55. I noticed that when I took the glue off the vent hole behind the driver the sound totally was ruined. I then covered it with a plastic bumper to see what would happen and it appeared to have even more detail. Not sure if it was this or the other thing I changed for testing.


I did two tiny changes today and one of these seemed to make the headphone a lot more brighter. I have no idea how on earth this could happen. Cymbals suddenly were sooo much better and almost what they sound like on my Grado.


It either involved putting a seal on the vent hole or allowing more air into the holes surrounding the driver.


Yeah I need to get rid of some of my old headphones. It's really annoying having this huge box of headphones out. I like each and every one and I hope someday I can stick with only two, but it seems impossible!




Originally Posted by HibyPrime View Post

Holy crap you put a lot of work in this lol... Hopefully if anyone has a ur-55 they end up reading this, it sounds like its a pretty big improvement.


Also, you have way too many low end phones smily_headphones1.gif

post #8 of 41
Thread Starter 


Edited by tdockweiler - 11/25/10 at 6:29pm
post #9 of 41

Hmmm...this is very interesting since I did something like this but with portapro drivers....

A while back my sr60's had died on me and i wanted some cans to use at home. I thought I'd get the portapros to save money and buy a reasonable sr60 replacement and i loved the sound but the metal headband was yanking out my hair like crazy, thus the modding began. My uncle had some old Sony mdr v150's and offered them to me since they werent working from there i took the drivers out, cut huge holes in the back of the earcups and decided to put the portapro drivers in and rewire them. The result was exactly what you mentioned: tight controlled bass, beautiful level of detail and a huuuuuuge soundstage. However one huge flaw where the pads that came with the sonys...the cheap pleather pads rested on my ears and not around making them very uncomfortable. So i decided to put the quarter modded comfies on them and test it out. My god the detail blew me away! the downside: They were TOO open...anything leaked in and out it was like speakers... I still have those koss drivers (very mutilated however) and managed to fix my Grados but unfortunately they have a balance issue (the left side is louder than the right)

post #10 of 41

I've been looking for a cheap pair of good over the ear headphones and these seem like the perfect fit. I stumbled across these on Best Buy's website, and considering I have a $20 gift card I'll probably go pick them up soon.


I've read your reviews, and if I get them I might try this mod. Thanks for all your time you have put into trying to get these headphones noticed, it will probably save me a good bit of money.

post #11 of 41

Interesting.  I've done several mods to my UR-40s and the improvements were quite real, even on a $20-30.00 headphone.  Bravo.

post #12 of 41

Nice post OP, I picked these up a few weeks ago and am really liking them. I wanna do your mod but I'm worried I'll mess something up, I think that's leading to me not being able to follow your instructions. You explained it pretty basically but I'm looking at them and thinking I'm going to do it wrong and break them. This might sound weird but does anyone have a video of the process? My brains just not computing. I went around the plastic line that's like a 1/8th of an inch behind the ear pads thinking that had to be what I needed to remove. But after going all the way around it still didn't want to come up.  


Yeah I'm a n00b, but I have bad luck and would hate to kill my new headphone.

Edited by quebert - 12/16/10 at 1:15am
post #13 of 41

Hi tdockweiler, to clarify, are you saying that the mod is to remove the metal grill from the back of the housing (with the Koss logo on), with a small screwdriver, and pry off, or have you opened the entire housing (into two parts) and removed the metal grill from the inside by unscrewing?


I'm interested in doing this mod, but need the modding process to be clarified before proceeding.(then I'll post the results).

post #14 of 41

Still not sure how this mod is done, so where you say "What you do is put a small thin flat screwdriver behind the plastic..", do you mean underneath the foam pads, or in-between the two halves of the housing?


Lifting up the two halves of the housing with a small screwdriver looks to reveal some screws.......so assuming that this is not the place to lift the plastic to get access to the film behind the metal grills?


If someone can add some more detail to this mod, I'll go ahead and do it, and post the differences it makes (basically desperate to add some more midrange and top end to these phones...)

post #15 of 41

It's OK, I've worked it out, the foam pads are mounted onto a thin plastic base, that is then glued onto the main housing, you place the screwdriver between the plastic base of the foam and the housing, then lift up, I'll post some pics in a bit.

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