So I was at my store and bored looking through for some information on if the new black portapros had any significant changes when I came across this thread. Being the greedy person I am I took the portapro that I already thoroughly enjoyed as far as sound and did the kramer mod. I then went home and "borrowed" my grado 225s cups to see if they would fit on the porta pro and if they did anything sound wise. The 225 cups dont exactly fit unless I have the original cover that I cut a hole with on but after listening to them I do have to say it does make a noticeable difference to me. Its not life changing but it is worth 10 bucks or so to get some new cups. Main difference I hear after a brief listen while I type this is a widening of the perceived sound stage. To be a bit more specific I'd have to say the overall bass is a bit more fulfilling with a bit more room to play with, mids are a bit more pronounced for me and the highs dont seem quite as abrasive to me because they arent right on my ear. To me it signifies a more "warm" sound meaning some more bass and mids are there to be heard.
Forgive the janky picture taking as well as headphones as I just kind of plopped them on. I'll have to buy those senn cups and see if that changes anything. I'm testing this on Radiohead - Nude, Pink Floyd - Pigs, Norah Jones-Don't Know Why, and Neutral Milk Hotel -In the aeroplane over the sea on a sansa clip+ on normal eq with all files being flac.
Just some notes for people doing this, 1)when I initially punched holes in the grill for the kramer mod the sound came out being a bit too much treble and not enough punch in the bass anymore but this may be because I made the holes all the same size, 2) be careful about distorting the shape of the grill as it doesnt have that much space between it and the diaphragm which you will hear touching the grill 3) obviously be careful with the grill as i said a second ago, the diaphragm is right there so it is easy to puncture.
Overall I'd say cups would be worth it. The bass is still the best part of these headphones and while they may become a bit more "airy" with cups they certainly still have a good attack and punch plus its worth it for the widened soundstage. Of course all of this is IMHO.
NINJA EDIT! : I found out that another pair of koss headphones (ksc75) have the same grill guard and I got those headphones for cheap (10 bucks when radioshack had them clearance ) So I took those out and fixed my error with the grill hole sizes by making the outside diameter ones larger than the inside ones. Thus the outside diameter holes are the largest the next ones closer in are a bit smaller and the one hole in the very center of the grill is the smallest. It fixes that having too much treble problem I said earlier. It pays to do it right kids. Also another note, if you're going to drill a hole through the grill make sure to clean up the edges of your cuts really well for little left over pieces of plastic because it only takes a tiny bit extra plastic for it to make contact with the diaphragm below and vibrate off of it
Left is the one with different size holes and the right one is the one with the same size holes. Note this is before I cleaned them up a bit of the rough edges.
This is what happens if youre not to careful and use a belt loop punch lol.
This last picture just shows you the difference in drivers between the portapro and ksc75 and give an idea that the grills are the same size and shape.
Sorry for the bunch of pics. Just thought i'd share my experiences with the mod and some tips to other people doing the same thing.
