Wachara,
Total area is 80 x 70mm, well...79.90 x 69.90mm to be exact. Diaphragm is a in-house sub-2 Micron PET. We tried 600Nm but due to the poor Young's Modulus, it was almost impossible to tension and/or get any decent bass. To successfully use a Nanometer film, I personally think the Matrix requires better filler geometry to improve the Young's Modulus but, with current Polymer technology it is difficult to produce such filler based thin-films at such thicknesses.
Diaphragms are manufactured by our other family owned Polymer company.