12/20/99: From John B on the MiniDiscussion board:

Top idea. Just modified my "plug", and it is way better. Better fit, stronger bass and better isolation.

1/7/00: From Jerry Johnson:

I couldn't wait to try your suggested mod for the The Plug headphones. I had sought out these phones for 2 months, looking for a headphone that would sound good and not "sound leak" while listening in bed late at night - don't want to disturb the wife. I thought the Plugs would be the answer but out of the box they were clearly lacking due to the poor fit of the pads. Now, with your suggested mod, they are finally listenable.... Thanks for the tip!

1/14/00: JKaiser in the HeadWize DIY forum recommends using a round toothpick to make the hole in the ear plugs and then use a drill bit (not a drill) to enlarge the hole. Complete instructions are in his forum posting.

5/1/00: JonR in the HeadWize DIY forum suggested this idea for making the ear plug holes:

Although reversing the Koss foam pieces worked well for my ears, I still wanted to make custom plugs, so I followed these instructions. But with the brand I use (my favorite for sleeping and on the bus) the hole wouldn't stay open. So I inserted a piece of electrical wire insulation and now there is a rigid "hole" and it stays open; the Koss tube is an exact fit inside the insulation.

7/7/00: Trevor Walton writes:

Ran across your page today, didn't realize there was a page describing that mod. Doing that was the first thing that occurred to me after buying them, not surprised the same idea has occurred to others... Anyway, to get to the point, have you tried using a red hot nail heated with a torch to simply melt a hole in the plug? That's how I did mine and it works quite well - smooth, clean hole. It is nearly effortlessly. Just gotta be careful not to burn yourself...

10/9/00: Leon Werenka had these suggestions for punching holes in the ear plugs:

- a leather hole punching tool - it typically looks like a handheld paper hole punch that has a wheel with 4 or 6 various hole sizes that can be rotated and punched.

- hardware stores sell the two pieces needed for putting snaps in clothing (like the front snap on blue jeans). Before they are compressed with a tool, one piece looks like a little funnel with a tiny hole. The edge is actually needed to punch through the cloth in the installation process. One of these could be purchased for a few cents and easily be pushed through the ear plug against a hard surface.

5/24/01: Mark Calder suggests that DIYers who have constructed the Koss Plug replacement cushions with a drill bit may want to "cauterize" the interior wall of the hole to prevent any foam bits from coming loose and lodging in the ear canal. Since the acoustic tube of the Plug presses against the interior wall of the cushions, I don't think it is easy for foam bits to come loose, but cauterizing the hole is a good safety precaution. The cauterization can be done with a hot nail (see Trevor Walton's suggestion) or with the simple heated needle method described above.

5/27/01: Major revision of article. Added description of heated needle method for making holes in the ear plugs. Also, added section on damping the Koss Plug transducers (modification #2).

5/27/01: "Duncan" in the forums reports on the latest mod (which was posted in the forums prior to this article update):

I've just done this mod (not as yet done the first one) and you are right, it does seem to equalise the sound. Admittedly I wasn't very scientific about it (ripped an earpad in half and placed it underneath the wire by the vent) but what you get out, as you say is quite listenable... not fatiguing (imo) at all anymore.

8/7/01: Richard Petrilla made replacement cushions for the Koss Plugs from Smith & Wesson "Quick-Fit" ear plugs, which cost about $5.00 per set at Walmart. He writes:

The plastic cord between the two sides easily slides off and this leaves a guide for you to bore a hole. You can use a drill, but I would suggest using a hot piece of straight coat hanger. My holes ended being very straight with this method. There is very little melted plastic mess if you do it quickly. I also cut the base just a tad to get the plug at its fatest part.

My plugs have a removable acoustic tube and no mute button. It took me a while at first but now I could do a pair of replacement cushions in five minutes. The cushions are installed on the acoustic tubes up through the middle.

Now for the sound. I like the isolation that the plugs provide. I used mine a few times on the plane and it blocks out a good portion of the outside noise. As typical with other in-ear plugs, the sound can change quite a bit by the way they are worn. If you leave them out a bit, they sound lean. If you push them in farther, they get bass heavy. I did eventually find a good balance and they sound respectable for the $20 that they ended up costing me. I find these to be more comfortable than the foam cushion pads but others may not.

8/7/01: Forum member Mail4U tried the mods on the new version of the Koss Plugs (removable acoustic tube, no mute switch) with these comments:

I did the complete cmoy mod - this needs to be done or it sounds very tinny. With the cmoy modification the treble smooths right out, though accurate bass is still a problem with the foam ear plugs. The midrange and treble to me are very liquid and non-fatiguing with the mod.

I replaced the foam mod with the Etymotic ER20 ear pieces ($10 + $5 shipping). Bass much clearer and isolation is excellent. Generally very smooth non-fatiguing sound. For total $30 cost can't be beat. Think it gives a lot of the under $100 phones a run for the money - the cheapskates Etymotic ER4P!"

12/9/2002: Jason Carr freezes his earplugs before drilling them. He writes:

For getting a perfect hole into foam earplugs, I compressed my foam plugs as flat as possible (end to end), and held them underwater while allowing to expand to them with water. I froze them, which allowed for a very clean drilling. Allow to thaw/dry, then mount as usual. Yippee! Perfect hole, straight, lovely.

The main advantage of this method is that the earplug is hardened (for greatest accuracy and ease of handling), and does not pick up soot from heated metal objects. The perfect and potentially larger gauge hole allows the plug to be kept at normal length for comfort and secure fit while not getting crimped as can happen with smaller-diameter holes.

12/7/2002: Tom Rons writes:

I bought a pair of Koss The Plug earbuds, because I have been wanting earbuds that went straight into my ear for a loooong time. I'm simple not satisfied with the sound level regular earbuds direct into my ear.. and everyone else on my bus ride. Immediately after I had placed an online order (the earbuds aren't available anywhere near me), I started looking around for sites with some more pictures and information on the sound quality, as I usually do (I always get obsessed with things like this for a while). Excited as I was, I stumbled upon your page (thanks Google!), and read about your mods.

I must say, at first I was very sceptical. I'm 17, and I have a mentality that goes either you do it right or you don't do it at all, so I wasn't planning on doing these mods at first. Also, because you stated the earbuds would be slightly less efficient after the modification. I also didn't think it would be necessary for me to mod them, as I usually don't hear any differences.

When I received the earbuds, I was very excited. I ripped the package apart and put The Plugs into my ears, 'Plugged' them into my sony NW-MS9 and hit the play button. After being deafened for about 3 seconds (the volume is always at max, which was pretty silent in my opinion, using all kinds of regular earbuds from whatever brand: Sony, Sennheiser, you name it!), I turned down the volume to about 60% and noticed the sound was just horrible. I usually kick on loads of bass, but not in this case. It was as if every bass kept echoing into my ear canal for a few seconds.. I figured if I wasn't going to try and mod these earbuds, I wasn't going to use them at all, like you did at first.

I printed out your project page and started gathering what I needed, aside for the foam ear plugs, the conical ones that came in the package fit me great for now! I used circular cut foam from my old Sony earbuds (the cheapest model with Twin Turbo circuitry) to balance out the bass and further dampen the sound that could escape through the vent holes. Then I used a drop of super glue to attach a string of foam over the canal on each side, to equalize the treble and act as a filter against ear wax (my primary concern ;). Not expecting much, I plugged in the earbuds (again, into the Sony NW-MS9) and hit play again, only to find out this was the best output any earbud had ever provided me with. Clear bass responses, hardly any interference for my direct environment, and at 100% volume on the NW-MS9 it gave me more output than I ever expected from a portable audio player (before, I was very displeased with the low volume the NW-MS9 provided). Thanks for a great mod, I'm sure it will continue to please many people in the future!

2/4/2003: The new version of the Koss Plugs has a soft, removable acoustic tube and no mute button. Stephen Runa (a.k.a. "Moonwalker" in the forums) sent in this version of the mod with special instructions for the new Plugs:

I posted few times about the Koss Plugs in the past, but now I think I found a way how to mod them so they sound their best. This post will help anybody who tried the mods from Chu Moy's project article and is still unsatisfied with the Plugs. The new procedures will be explained in detail, the ones included in the projects will be only mentioned shortly.



Step 1: Buy some ear plugs and burn hole through them - the supplied ones are very poor quality (as explained in Plugs mod article).

Step 2: Open enclosure using knife (as explained in the Plugs mod article).



Step 3: Use sticker of cca. 5 mm square size and place it inside the small bowl part where cable enters enclosure. The purpose is to close the rear venting (6 small holes). I tested the Plugs have better sound balance when rear holes are closed. After the rear vents are closed, the Plugs no longer produce the annoying squelching sound of the air-crushed diaphragm, when air is trying to equalize pressure on inserting into one's ear.



Step 4: Look at transducer - there's small hole in the middle of it. It's because the magnet is hollow, but for some reason, in the Plugs the manufacturer decided to block the rear hole with some glue. This make waves of some frequencies assymetrical and worsens the sound. I used pure alcohol and small tweezer to remove the softened glue and free the magnet hole.



Step 5: If you have the new version, there's soft removable acoustic tube that can be prone to loss. Remove the tube and apply drop of glue to the outer side of the short solid tube. Wait few minutes, then reinsert the soft tube. Don't use fast drying glue - it's too strong and you may not be able to detach the tube if needed in the future without damaging whole phones.

Step 6: There's also small piece of foam on outer diameter on the back side of the driver. Remove it, since there will be of no use because of the much larger foam inserted in the next step.



Step 7: Now complete the enclosures and listen to some full-specrum sounds/music: the drivers are often very poorly matched, so there's usually more bass on one channel. The side with more bass will need larger piece of foam. Open the Plugs again. Cut a cylindrical piece of some soft foam (diameter=13mm, height=4mm) and put it in the rear enclosure to the channel with more bass emitted. The foam will fit in nicely, expanding to cover entire inner space. Be sure the cable node is under the foam, not touching the driver. This may affect sound quality. Close the modded plug and compare with the other channel.

Now listen and you will notice there's less bass, more mids and trebles and more balance to the sounds. The other channel was initially less bassy, so it will need smaller foam damping. Use the same diameter (13mm), but cut it so it's height is only 2mm, or roughly one half of the first piece. Now listen for bass balance of both channels and enlarge or reduce the smaller piece of the foam as necessary to obtain the best balance. Remember: leave the larger foam untouched - the larger, the better (less peaks and muddy, loose bass).

Step 8: Open phones last time, remove drivers, fix them on the table in diaphragm upside position. Use hair dryer on minimal flow setting from close distance (2-5 cm) for no more than 4 minutes. I watched the temperature using contact thermometer, the safe temp is about 93-98 degrees Centigrade. This will loosen any stresses in the diaphragm material, and tighten the voice coil. You can also use the pliers too to hold the drivers in diaphragm upside position for the hair dryer "de-stress" process. Just secure the magnet section (now upside) between the jaws and apply hot air on the driver.

Remember using this procedure only on cheap phones, not on Senn HD-600! Do not use higher flow settings, the hot and soft diaphragm dome may collapse! When this happens, use small, weak sticker to re-form original shape of the diaphragm. After this 'cure' the sound of the drivers is much!!! less peaky, less bassy and much more close to each other - easy proof of different stresses in individual diaphragms from the factory.



Step 9: Let the drivers cool down, put together the canalphones and let the bass-heavy music flow through them at their max. allowable rated volume for at least 3 hours. If you hear diaphragm clipping or hitting the enclosure, reduce immediately volume a bit. I used short skewer shallow inserted into the soft tubes to reduce noise coming from these phones on the burn-in phase. (This doesn't work for old hard tubes - the holes are too small.)



Now you have near perfectly matched drivers in cheap canalphones. Sound is relaxed now, less bassy, more mid present, not fatiguing at all! I wish I did it first day I purchased my Plugs. I hope all of you will be pleased as much as I am!

PS: I'm not responsible for any damage you can do to your equipment/phones/health or any other damage/injury beacuse of proceeding with my guide and making the suggested mods. Happy listening!

2/4/2003: Richard Chacon (a.k.a. orl2222 in the forums) has a mod for the new version of the Plugs:

I recently bought the new version of the koss plug. I tried Chu Moy's modifications. However, on the new models with the removable transducer tubes, they still sounded too "bassy" for my tastes, also the "rubber" transducer tubes didnt seem to allow a tight fit with my ears, not like my Etymotic ER-4Ps. I then decided to try something.I proceeded to cut off the "tube" of a ball point pen,(making sure it was throughly cleaned with alcohol)enlarged one end, and inserted it over the small tranducer tubes, cutting it to fit snuggly with the foam ear plugs as suggested by Chu Moy. I was also able to use a couple of Ety "rubber" tips also over my makeshift transducer tubes. The difference was night and day. The boominess of the bass was gone, midrange and treble were smoothed out. If you have the new model of the plug, try this you will be amazed at the difference.



The modified Koss Plugs are hooked up to my Sony D25-S. pcdp. I mainly listen to classical, and jazz. With the Ety 4 rubber earpieces attached, i get more of a well balanced sound. With the foamies, they sound more bass orientated. Isolation is good, blocking out 90% of outside noise. I've found that positioning the modified Koss Plugs with wires coming from the top of the ears, rather than the bottom like my Etys, provides better sound and more isolation. I've also found that I can listen to them at night, without discomfort while sleeping.

What I've done is completely remove the rubber tubes, and enlarge the plastic Pen tube using some small Phillips jeweler's screwdrivers by heating them up with a lighter, then enlarging the hole so that it fits on the end of the Koss Plugs. Once you take off the rubber tubes from the Plugs, you'll see what I mean. The replacement "pen" transducer tubes are approx. 1 millimeter in length. I used some super glue to "glue" the pen tube transducers to the Koss Plugs. I've found that using the Ety 4 "rubber" ear pieces to provide the best sound to me. The foamies tend to accentuate more bass.

Overall the modified Koss Plugs sound a heck of a lot better than my sony MDR-EX70s. As compared to the Etys, the isolation is just as good. Sound wise, I'd say they are a notch below my Etys, but not by much - a heck of a lot better than any other ear-plug headphones out on the market currently, except of course, my Etys. Put it this way, my sony EX70s cost me about $70. These modified Plugs sound a whole lot better than those. Don't forget to put in the pieces of old ear foamies behind the transducers. Instead of a pocket knife, I used a single edged razor to open up the koss ear plugs. Also, I've found that positioning the Plugs with the wires coming from the top of your ears works best.

I suggest ordering some Ety 4 replacement ear pieces (not the foamies) from HeadRoom for people who don’t have Etys. They are priced at $15 for five sets. Hope this helps. Attached is a picture of the modded Plugs. They do say "Radio Shack" on them, but they are the Koss new style Plugs. I just found them a couple of bucks cheaper at Radio Shack.

Go to Addendum page: 1 2

Questions or comments? Visit the HeadWize Discussion Forums.