I put everything together and the sound that really impressed me the night before was back! It's not the Aska foam and it's much lighter, but just as thin, but not hard. Why would that make such a difference? The mids are now sooooo good and maybe a little forward it seems like. The treble hasn't really been changed much. The sound is now fairly balanced and everything sounds natural. Bright songs that would drive me crazy on any headphone, still do. I want that. The bass is now not bloated and as good as I remembered. The bass is so good on these and makes my HD-650's bass almost like a joke. What's funny about these headphones is how clear they are.
Unfortunately my ears are now ringing and tired due to all this modding. I'll be able to listen to them more tomorrow. For some reason adding that foam was what caused the biggest difference in the sound! I tried some pillow stuffing but that was terrible and drowned out the mids somehow.
It's really quite amazing how every tiny thing, no matter how small can change the sound.
I don't know if this is my imagination, but it seemed like whenever I added more material to the cups, the mids would come forward a little more. Only when I added that foam (nearly touching the driver) did they sound extremely good. They may be very very slightly too forward now. Maybe if I trimmed a little off the foam, the mids will be less forward. I'll see tomorrow. It could be they sounded too forward because my ears were just ringing and I'm tired. I'm going to try these for gaming too, just for my own amusement.
I know what you mean re: the 650 and bass. My 650's just don't get picked up for use anymore. You raised tons of issues, too many to comment on, but a couple of suggestions from one who has also lost a lot of sleep in this process, and who has been "done" multiple times.
1) If you had a channel cutout, it's possibly the rotation of the locking cable, or a bit of corrosion or debris in the jack. Happened to mine before I figured that out. A few insertions and roatations seemed to polish it up and no more problems.
2) You'll never be done. Live with it. :-)
3) You are using a lot of materials that haven't been discussed, so it's very hard to give feedback. Photos would help should you ever really want feedback...
4) I have found now that even some "bright" songs that used to bug me no longer sound bright, but other songs don't sound muted. I'm not sure what's behind that. My theory is that so many 'phones have so much top end sizzle and distortion increasing brightness that a small excess of energy overlays extra distortion to tip the sound into become irritating. Without the injection of HF distortion, that extra brightness is there, but not to the level that annoys me. David Bowie's "Heroes" has always been a favorite song, but it's not been easy to listen to due to excess brightness. With the "Rastapants" mod completed, it's surprisingly quite smooth.
5) From your description of the foam you picked, I would guess it's an open cell structure. If you can blow "through" it with ease, it's probably not doing much which is why you need a lot. The Akasa foam is moderately open cell, so it does a good job sucking up energy and preventing reflections from the back of the cup. If you are having to fill the cup with your foam, it's probably less acoustically damping, so you need more (if it's closed cell and I'm not sure what's going on at all!). A lot of foam will decrease the volume of the cup, and drive up the F3 (low frequency cutoff), so you'll want to make the vent as open as possible. Just my guess based on your description, I could be TOTALLY wrong about the foam...
6) With rastapants, because the driver is open to my ear, I had to actually reduce the vent to tune the bass for optimum extension and clarity. Foam and what's directly in front of and behind the driver have a huge effect on what the vent is accomplishing. Electrical tape on the outside of the vent is an easy way to tune the bass (and has a big effect on midrange).
7) Plasticine (modeling clay) is a lot denser and therefore more effective at killing resonance in the front baffle than blue tak. It's worth the $5 to buy a chunk of modeling clay.
Lastly, if your ears are ringing, I seriously suggest you turn it down. That should never happen, it causes temporary or permanent damage with every occurance. Your ears will easily adjust to a "new normal" after a short while, to make lower volume sound fine. Protect your ears to enjoy your phones longer... Sorry, can't help myself on this one. Hearing loss is forever...
Edited by mrspeakers - 3/25/11 at 10:57pm