SB Acoustics SB29SDAC-C000-4

The THD measurements at voltage levels 2 - 5.6 V were carried out with High Pass Filter "on" (2nd order Butterworth type, 600 Hz cutoff, HPF2-600)

When making measurements using log sine sweeps the tweeter back chamber cap vibration was clearly evident at some frequencies. The cap made of thin plastic and has insufficient stiffness and vibrates under the sound pressure from back side of the tweeter membrane. This effect can be seen at comparing diagrams "Scale 5 Ohm" and "Damped_back_chamber" of impedance frequency response in a form the spike around 2 kHz. For damping the back chamber cap it was sufficient to firmly attach the palm to it and the effect disappeared.