Perhaps because positive experiences with tuning speakers in the past, I couldn't help tweaking further the ear pads of the 007.
After trying a variety of materials inside the pads, it was shocking how different they all sounded - much bigger differences than between amps. Will post a report with pictures soon, but the good news first: I ended up with an ear pad mod that makes the 007 Mk1 sound quite much more open, with much bigger sound stage, and also with more defined and snappier bass (or another option for lush, wet, softer bass lines a la old reel tape players, depending on your taste). In parallel, I have also experimented with the TH900 with the goal to get the mids work better - and I have very good news there, too.
Out of the available stock pads for various headphones, the SR Omega and the 009 pads may be the best choice for the 007, but couldn't find any source for them, original or 3rd party - so these remain to be tested.
Some more details on this.
Having two sets of brown 007 pads, I decided to destroy modify one of them to imitate the SR Omega pads. During the previous (http://www.head-fi.org/t/677809/the-stax-thread-iii/2040#post_10459375) experiments, I noticed tendencies I wanted to check further. So far, no springs, inner earpad foam front side trimmed ~2 mm, opening made larger cca 4 mm in diameter.
Now it was time to adjust the leather pad to these, and experiment with various fillings.
Undo the sewing and take off the inner cover (on the right) and the other side of the flank, resulting in 3 parts: the inner cover (below), the inner flank, and rest of the ear pad.
First, enlarge the opening by cutting a circle:
The result is circular, rather than the original trimmed circlar shape (this was intended).
Do the same to the other part:
The results so far:
Then, redo the sewing (manually or with a sewing machine, depending on your skills).
Note that since the inner diameter has been increased, a ~3 cm long leather extension is needed for the flank.
When sewing, leave the extension part to the end, then cut as it's required and finish the end.
In the next phase, cut new fillings and assemble the ear pads.
The picture above is just to suggest the thickness in the front.
Next, I experimented with the ear pad fillings. The method was just to push the pads against the drivers (without mounting) and try that way for gross comparison. Then, the winner combinations were tested assembled on the drivers.
I have tried 5 materials for the filling: (a) the original foam, (b) open cell foam, (c) active carbon filter pad (for house ventilation machines :), (d) polyester fiber acoustic pad, (e) natural wool felt pads. I ruled out non-carded natural wool filling as it was not practical. The selection was based upon what materials I had at home from earlier speaker tuning, but there may be a lot of materials which sound better than these. One thing to say, there was considerable difference in how did they sound compared to each other:
- original foam has softer, rounded bass lines, good slam, kind of old reel tape sound
- open cell foam had somewhat cleaner bass, and it's still foam (easy to deal with and people are used to it)
- active carbon filter pads increased the effect above, resulting in very spacious, deep, extended, clean bass with superior piano/base strings attack and decay, also making the treble cleaner, and somehow the timing was more consistent over the frequency range, resulting in higher perceived PRAT and resolution
- polyester pads were OK but nothing special; slightly softer sound but so much as the foams
- wool felt is tricky, since it depends very much on density, much more than for the rest. I had medium density pads, they took away all boominess and dark signature, but the results were a bit too shiny perhaps.
Since the carbon pads were quite stiff, I have put a very thin layer of polyester pad on them, and ended up using this.
The carbon pads are 14-15 mm thick (angle-trimmed 2 mm in the front), and the poly pad 2-3 mm.
I have tested the same things for the TH900, with the same tendencies, and end result, so this seems to be pretty consistent so far. The sound stage with these pads is huge both in width and depth (perhaps higher, too), and pin-point. Saxophone sounds more direct and velvety, as do synth and strings, violin/cello has more physical body, piano is more transparent and resonant - all welcome.
I have tested again using the springs, but again it sounded better without them. However, that is an option to make a darker, more distant sound.
Now my 007's sound the same open as with the previous mod, but with the differences described above with the carbon pads. I am eager to compare it to 009 and other flagships, and will get back in a few weeks with the results.
Meanwhile, if you can source SR Omega and/or SR-009 pads, please notify me, too :).