I finally had some time to do a couple of Bilavideo's mods on my pair of 325i and thought I'd post my findings.
THE GRILL CLOTH MOD -
I used a right angle dental tool away from one of the holes to snag and then slowly lift the grill cloth until it tore. I was then able to pull off most of the cloth with my smallish fingers. The dental tool made quick work of the remaining threads. I thought I'd just live with this first mod for a few days before trying the hole mod so I did nothing else.
Listening, I could well understand how one could notice little sonic effect by tearing off these grills, especially if they don't have good aural memory or didn't listen to the same tune immediately before and after the mod. But thankfully I was able to notice changes. First thing that surprised me was that cymbals became sweeter and cleaner. Some high level transits that were a little rough before were less so now. There was more high and low level detail present...instrumental and vocal lines were easier to follow for instance. And I noticed imaging effects I hadn't heard before too. It also seemed the whole frequency range was louder (I was able to turn the volume down a notch) EXCEPT in the bass? To me the bass sounded a little drier, or less fleshed out. Even with the bass turned up on my Sansa Fuze player something still wasn't quite right compared to before (I think it was the EXTREME lows that were effected but I wasn't 100% sure). Why the bass was now a little anemic I couldn't say, perhaps the more noticeable mids and highs just obscured the bass a bit. Still with the increased detail and sense of ease I heard taking the cloths off was worth it. But I'm curious if anyone else who has just done the grill cloth mod also noticed reduced bass.
THE HOLE MOD -
I pulled off my medium length Head Coverage wood cups and used a bic pen to make the four holes as show. (If I didn't do the pic paste thing right the link is h**p://img218.imageshack.us/img218/5787/img26702.jpg). Oh, and I didn't do any damping. The very lightweight foam on the magnet back that you see was stuck on a couple of years ago but effected little to no change.
Listening. WOW...now there's the bass! Perhaps even a little too much bass. These longer (than stock aluminum) wood cups already naturally strengthen the bass so if you're using something similar I'd recommend you first try just two holes and go from there. The bass from these phones is now very satisfying compared to the pre-hole mod state. But it's only in bass strength and bass detail where I heard any change with the hole mod. All other improvement were wrought from removing the grill cloths I thought (but others may experience differently).
There is a little something extra about the hole mod that some might find difficult to believe tho. I'm slightly hard of hearing in my right ear...a reduced sensitivity across the entire frequency range if you will. With music systems and equipment without balance controls I'm always struggling with any headphone. In such cases I'm constantly pushing the headphones right driver closer to my ear trying to get a correct left/right balance. So when punching holes in my 325i I thought I'd try an experiment. On the left side instead of widening all four holes I left two of the holes with just the original pen point hole without widening. Well guess what, I definitely notice a balance shift and am not pushing the right driver towards to my ear anymore. It's now as it should be, some program material is slightly shifted to the left, and some program material is slightly shifted to the right...I'm very relieved and thrilled!
I've always known that ultra small tweaks in vinyl playback systems could make large sonic changes but I wasn't expecting this in a headphone...very surprising!
So I'm wondering just what the next Grado headphone mod will be. What I foresee is an inert adjustable 2 piece felt/fabric/paper system replacing the stock black felt/fabric hole covering. One semi circular piece fixed to the plastic and flanking the hole area (but not covering the holes) has a raised rail on each side of the holes. Another semi circular movable piece with holes rides underneath the first piece's rails. This movable piece with holes has at each end a tab with hole or loop that can be pulled to infinitely vary the amount of flow from all the holes at once. I mean pulling the tab on one end of this second slide piece would open all holes to whatever degree you want, pulling the other end tab would close all holes to whatever degree you want. Perhaps even a thin pin/rod could be used through the cups grill to mate with the tab's hole/loop for adjustment negating cup removal. Such a system would cater to those who like/need to tweak and fine tune for proper tonal and output balance.
Thanks again Bilivideo for these great mods. Cheers.