The titanium nitride coated dome - so called TPM True Piston Motion technology - dramatically improves stiffness with obvious benefits in transient and intermodulation distortion response. With its very high value of elasticity modulus (six times higher than standard titanium), the ultra-thin nitride coated film applied both sides of the dome doubles the treated dome stiffness. The piston frequency range motion extends then by 25% when compared to regular titanium diaphragm, showing a predictable, ideal frequency response decay and avoiding top-end spurious resonances. This results in a more natural sound character up to the top end part of the spectrum. The nitride-free ellipsoidal suspension shape has been designed to maintain constant titanium stiffness, assuring a 3rd harmonic distortion lower than 0.05% over the whole working frequency range.