OK, allow me to answer this as gingerly as I can. We all know through our readings, that Grado has some variation of sound among their same model. For example, it has been noted on more than one occasion, that people have heard Grado model "X" sound one way and then when they heard another pair of model "X", the sound was different. With that being said, it's hard to predict fully how your results will end up if you decide to take the ink pen to the holes and cover them with the felt. However, do keep in mind that one of our members - Chris, has found that buying some muslin fabric from the fabric store is an excellent restoration fabric to use if you feel that you've opened up too many holes. I believe he tried felt initially, but it didn't work as well as the muslin fabric did for un-muddying the bass.
I wish you were a bit closer to me. You could hear a pair of SR-225 Grados with all 10 vent holes opened and the felt applied - as well as the loin cloth removed. However, they are in a set of Cabillas cups, you'd still be able to decipher the sounds based on your music and what you currently hear with your stock SR-225i ... before putting them under the surgeon's knife.
After hearing nothing but headphones with modified drivers over the past 2 months (with the exception of the stock Alessandro MS-Pros) and now hearing Marty's SR-325i Grados, I sort of wished two things had happened first.
- That I had put several hundred hours of play time on the headphones before popping some holes open.
- Used the drivers in the wooden cups after the proper break-in to determine if the bass was at a good enough level for me
Now, with that being said, I might consider moving towards the following modifications on my SR-225 and my MS-1i headphones:
- Remove the felt and install some muslin fabric and see if I can restore the sound and tone of the bass as close back to "stock" as I can.
- Keep the Dynamat installed on the rear magnet of the drivers.
- Switching over to silver cables to see if some of that Grado "sparkle" can be restored a bit.