As others said before, they (the springs) elevate the pads away from the plate, and also keep distance from the ear.
I have tested a lot of times with and without them, with various combinations of pads filling, but every single time I liked more the sound without them.
That applies to the 007 Mk1 and 007 Mk2 (current model) - note that the 007 Mk1 spring is slightly larger, and it's assembled in slightly different way than in the 007 Mk2.
Even better, you can put 009 pads on the 007 (both Mk1 and Mk2) and they will sound more open - the 009 pads don't accept the springs, and they are not needed.
My recommended minimal (and reversible) mod on the 007 Mk2 is this:
1) remove the springs, then if you are brave,
2) take out the filling from the ear pads and cut off the 4mm thick white styrofoam reinforcement from the foam filling. I used a ceramic knife for that and when finished, I could glue the foam back with the original glue layer (if I wanted).
3) re-adjust the head band.
The sound becomes cleaner and more open, bass will have more texture and definition, too. I have also measured them both ways and the measured difference is nearly none, while the sound character did change.
You can combine this with Spritzer's port mod, and decide which combination you like most. FWIW I have left the port open on my Mk2.
On the 007 Mk1, the best sound (and closest I've ever heard to the Stax SR-Omega) is (so far) obtained as follows:
1) remove the springs,
2) use the 009 pads, but cut off the 4mm styrofoam reinforcement and
3) replace it with 2-2.5 mm thick carbon foam inserts: about 4-5 cm long and 15 mm wide crescent shaped one at the back side, and 2 cm long 10-15 mm wide on the front side.
4) re-adjust the head band: start by making it wider and flatter and bent more inwards on the ends, then work your way backwards until you find the best bass impact with largest sound stage.
The change in sound is absolutely shocking. It opens up, sounds more dynamic, much larger stage, and very smooth and natural. I thought my modded TH900 has killer bass, but this is better, and it's better at everything than any Stax I've heard this side of the SR-Omega (including the 009).
Modding the 009 would IMHO make most sense with changing the cables to solid core pure copper and take care of the capacitance. The pad mods don't help the 009 as much as the 007's (the 009 is the most consistent, neutral and reference level Stax I have heard so far), but there is slight change into warmer sound with more bass impact if you do the mod above (you can leave out step 2 if you want, and just add the inserts below the white styrofoam disk but inside the leather pad). However, I would leave the 009 alone, it sounds pretty optimal in stock form. Eventually consider the cable change and/or use a darker/deeper/relaxed sounding source.
IME all these converge in similar directions, towards the listening experience that I've heard with the SR-Omega, but approaching it in different ways and to different extent. The modded 007 Mk2 would be my choice for jazz and small chamber, perhaps for EDM too. The modded 007 Mk1 is good for everything, really, it makes everything sound good since it's so smooth and fluid while dynamic and big sounding, and sounds closest to the SR-Omega. The modded 009 is... well, a 009, with some flavors, and the results will depend more on the ancillary equipment, as it's very revealing. Each to his/her own.
