Thanks Purrin for making the measurements of my headphones. 

For your information, these are the specifications of the headphones you measure:

1.  Active diaphragm diameter: 80 mm.
2.  Spacer thickness: 0.5 mm.
3.  Diaphragm thickness: 3 microns.
4.  Stator and spacer material:  1 mm and 0.5 mm copper clad PCB respectively.

My diaphragm diameter is actually 2 mm larger than that of SR007.

I'm not sure what is causing the resonance.  But I feel that the diaphragm diameter is a bit too wide.  This makes tensioning the diaphragm quite difficult.  I have to put a lot more tension on it in order to make it stable.  Could this possibly be the cause?

Wachara C.