Here is a picture of a pair of KOSS KSC-
50 headphones which I purchased on eBay.
These headphones were less than $10 U.S.
These are great sounding headphones,
namely because they use the same speaker
from the KOSS Porta Pro line, just put into
a more "sporty" housing.

For some people however, these clip on
headphones  may be a little uncomfortable  
to wear. Also, due to the gap between my
ear and the headphones, a lot of the bass
was being lost. To fix this, I put the KSC 50
drivers into a better headband. Here are
some pictures I took of the process.
The packaging, and two shots of the KSC
50s, with one showing the inner sponge.
The headphones would slip off as soon as I
leaned my head over.
Okay, now for the fun part. I don't even
think the headphones were an hour old
before I took them apart.
Here is a picture of the sacred KSC-50
driver, which  is what all the fuss is about.
I am going to put the KSC 50 drivers into this
headset. I found this headset at a local salvage
shop, and paid about one dollar for them.
I was fortunate this time because It turned
out that if a  cut was made on the old KSC
housing along the blue lines shown, the
remaining piece would fit nicely into the new
headset, pictured above. All that was needed
was to just add a little glue to hold the cut
piece onto the headset.
Here are some pictures of the headphones all
finished. The bass is much better now, since the
drivers are pressed against my ears. Also, they are
much more comfortable to wear, which is very
important for long listening sessions.. There is a
little piece of the old silver KSC showing, and I will
leave it on, instead of painting it black.
Look at the strange left overs, they look like the
remains of a space ship!
A Way To Modify the Koss KSC-50 Headphones to Improve Sound Quality and Comfort.