The Reversible Bass Mod elevates the bass and slightly attenuates the upper mids and treble frequencies as described by many others in this thread. The sound quality changes are audible and an improvement, IMO.
I'm going to try felt and other materials to partially open/block the bass ports and some ear side of baffle mods, too.
My simple DIY measurement kit is shown and my methods described HERE.
Here are my graphs. Take them FWIW.
EDIT: VARIABLE Bass Port Mods and Measurements
1. Stock = Sealed Bass Ports ---> Not enough bass
2. Bass Port Mod = Fully Open Bass Ports after removing the Stock Tape Disk from each driver makes a 2.5 mm bass port ---> Too much bass
3. Partially Open Bass Port Mod = 1.8 mm hole using Double-Sided Tape ---> Just right amount of bass
4. Partially Open Bass Port Mod = 1.3 mm hole using Double-Sided Tape ---> A little more bass than Stock
5. Remove ear side foam disks = Too much bass
Compare to the graphs, above, and draw your own conclusions:
EDIT: Here is a photo of double-sided tape with a 1.3 mm hole.
To my ears, a 1.8 mm Variable Modified Bass Port falls in The Goldilocks Zone and sounds better than Fully Open (Stock Tape Disks Removed), Fully Closed (Stock Disks in Place), and 1.3 mm Variable Modified Bass Ports.
I used a hole punch with 6 different sizes. The smallest size punch = 1.8 mm and makes a uniform hole in each double-sided tape disk. I usde a thumbtack and toothpick to make the 1.3 mm holes in disks shown in this picture and the holes are not uniformly round. A hole punch is recommended.
turbobb's youtube video shows how to get to the bass ports...Well Done!
Edited by bluemonkeyflyer - 8/8/14 at 6:23am