I had the same issue with driver touching the ears with it removed.. but doesn't putting the spacer back cover the holes cut out and defeat the purpose? As yet I haven't done this mod but want to do it soon, still not convinced it will help the he400. What they should do is have spacers made of the same foam material that is inside the pads.
No - depending on how and where you cut the holes, many remain exposed and can be there to capture reflections (I assume). In my particular case, I can see some of the holes I cut, while others are partially / completed obstructed. If I could do it over, I would keep my holes as close to seam as possible. As it is, I am pretty close, but could have been a tad more aggressive. That way, no matter what, the holes would have maximum overhang into the listening area and probably capture some of the sound as it radiates to the ear.
With the spacers installed, looking at the cans, what you end up with is probably 1/4 to 1/2 inch 'cylinder' firing at the ear. The pleathers / ear lobes absorb/reflect some of the sound energy as it travels to the ear. No question that the pleather has some overhang - not blocking the drivers, but certainly posing an obstacle in what would otherwise be a cylinder tube strapped to you ear. Question is, by letting the drivers be closer to my ear, am I doing a better job of minimizing unwanted reflections? Second question would be, do we have an issue wherein a square planar wave front travels badly through a round hole?
In any event, even without the spacers, reinstalling the pads places them against the plastic retaining ring. That ring has holes in it, yes, but the whole circumference of mount ring / pad surrounds the driver and does not really expose the holes to the driver any more without the spacer ring than with it. But it does potentially add more distance between the driver and your ear, and does add another more surface are to cause potentially more reflections I suppose.
Its a tough question - there is little data to go by, and I can't assume that my end result is the same as in the JERG guide, which, btw, only shows a slight smoothing out of frequency response in the 1 khz - 6 khz range mainly. I am not sure that there was a big impact on decay.
As far as I am concerned however, the basic mod - cutting some holes and cutting out excess pleather from the plastic ring is an improvement. I am willing to bet that the right pads would make a big difference in terms of improving damping. Stay next to the seam and try to get two rows or so, and you will probably get a maximum impact. I may take an exacto knife to mine again / remove spacers again with the same songs and have another listen.
I'd like to stuff a wad of poly-fill into the cups to see what happens. Has anyone tried that?
Edited by MrMateoHead - 12/18/13 at 12:54pm