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So, let's turn "on-ear" Koss PortaPro fragile headphones into over-ear real comfy headphones thanks to modding KOSS UR-40 !

 

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At first, use some plastic adhesive tape to remove the poor quality pleather from the original earpads and you will get low-cost velour comfy earpads:

 

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Now 3 screws to be removed to open the cup of the Koss UR-40:
1 at the top of the driver position and 2 at the bottom right and left:

 

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And there it is! The famous 60 Ohm Koss driver!

All you have to do is gently pull out the upper plastic black tip with a flat screwdriver to remove the original 40mm titanium coated black driver (not shown here) and replace it with the blue (from original PortaPro), black (from SportaPro) or even silverish driver (from the 25th anniversary version).
Solder a new cable and remove the thick foam that covers the grill in the earcup to make it sound like open PortaPro headphones.

 

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The cables you see on this picture are from Sony mdr-v300 DJ headphones (needing a previous cutting of the inside end of the black silicone guide of each earcups exit to slide it into it easily) and from the white version of the more recent Sony Mdr-zx610ap (needing total removal of the 2 silicone tips earcup exits).
P.S.:
The super soft grey velour earpads seen on the left UR-40 DerfMod version comes from old wireless Thomson headphones Whp-565 and fit perfectly here. Adding some foam under them ameliorates the wearing comfort. Easy as 1 2 3. King of mod. Enjoy!

 

[mysticstryk]

Very nice!
 
I found a pair of these headphones buried in a friends closet.  I asked if I could have them and toy around with them.  I ordered a sportapro and am going to do a similar mod, just for kicks.
 
The sportapro driver is the same as the portapro correct?  Just a different color?

 

[ROOMBAZOOM]

Hello!
Yes, it is. Black plastic back for sportapro, and blue for portapro.
I think both are made out of mylar (?)... and sound similar if not identical.
Be carefull of fake sportapro on ebay... They sound like crap with less bass and définition.
Have fun with modding Koss UR40.

 

[mysticstryk]

Hello!
Yes, it is. Black plastic back for sportapro, and blue for portapro.
I think both are made out of mylar (?)... and sound similar if not identical.
Be carefull of fake sportapro on ebay... They sound like crap with less bass and définition.
Have fun with modding Koss UR40.

 
Did the mod a couple weeks ago.  Got a sportapro off amazon for cheap.  I also took out the foam behind the drivers on the ur40.  I'm just using the cabling that was already attached to the sportapro drivers.

 

[Music Alchemist]

I owned a UR40, KSC75, and KTXPRO1 at the same time. The only one I still own is the KTXPRO1, because it sounds a lot better to me overall, and even more so with EQ. I actually like it more than most headphones in the three-figure range, which is quite impressive considering I only paid like $15 for it. Interestingly, the KTX and KSC have the same drivers (if I'm not mistaken), but different enclosures, and thanks to this they sound different. The KSC had more sparkly treble and a more spacious soundstage due to resting away from my ears, but the mids and bass were hardly better than Apple earbuds. Pressing them up against my ears didn't improve the sound either. I was going to write more about how the three headphones compare, but I'm lazy. haha. Since all three are so cheap, it's easy to compare them, so if you're curious and want to see which you prefer, you can do so for barely over fifty bucks.
 
Oh! And if anyone knows of mods for the KTXPRO1, please share!

 

[ROOMBAZOOM]

Hello Music Alchemist.
 
From my findings on head-fi KOSS UR-40 and KOSS KTX-PRO1 share exactly the same titanium driver.
So you should take the UR-40 and try to remove the grey foam covering the back of the driver and change earpads for velour ones.
Add some foam under padding to improve bass response and aura-nomic comfort.
Or - considering that your KTX-PRO1's drivers are burned in (though I am not a "burn-in effect" believer) -
just put them into cups of UR-40 DerfMod and enjoy the comfort of circum-aural open headphones.
 

http://images.google.fr/imgres?imgurl=http%3A%2F%2Fwww.head-fi.org%2Fcontent%2Ftype%2F61%2Fid%2F1040468%2Fwidth%2F350%2Fheight%2F700%2Fflags%2FLL&imgrefurl=http%3A%2F%2Fwww.head-fi.org%2Ft%2F690682%2Fthe-non-grado-driver-grado-thread%2F150&h=263&w=350&tbnid=P_oUvB8z_vTLgM%3A&docid=KSF1cvgepgkDRM&ei=5_d8V5vyF4XOa6b7nrgD&tbm=isch&client=firefox-b-ab&iact=rc&uact=3&dur=4443&page=2&start=15&ndsp=16&ved=0ahUKEwjbgdrt6d7NAhUF5xoKHaa9BzcQMwg8KA8wDw&bih=548&biw=1138
 
Thanks for reading.
 
Post-scriptum:
To answer clearly to the question debated at the very first page of this thread,
factory sealed Koss UR-40 definitely are half open-back headphones.
Koss website information on UR-40 is mistaken when describing them as closed ones.
Nevermind we love you still, John C. Koss...

 

[Music Alchemist]

  Hello Music Alchemist.
 
From my findings on head-fi KOSS UR-40 and KOSS KTX-PRO1 share exactly the same titanium driver.
So you should take the UR-40 and try to remove the grey foam covering the back of the driver and change earpads for velour ones.
Add some foam under padding to improve bass response and aura-nomic comfort.
Or - considering that your KTX-PRO1's drivers are burned in (though I am not a "burn-in effect" believer) -
just put them into cups of UR-40 DerfMod and enjoy the comfort of circum-aural open headphones.
 
Thanks for reading.
 
Post-scriptum:
To answer clearly to the question debated at the very first page of this thread,
factory sealed Koss UR-40 definitely are half open-back headphones.
Koss website information on UR-40 is mistaken when describing them as closed ones.
Nevermind we love you still, John C. Koss...

 
Hi there. Thanks for the info. I thought the UR40 driver was a lot larger? I'm not worried about it either way. I usually use high-end headphones and will upgrade to ultra-high-end once I can. I'm only using the Koss at the moment due to financial circumstances.