Midrange Driver with honeycomb membrane @ 6093 Hz
Bending mode - sound pressure related decomposition of movement

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Total Vibration
 

In-Phase component

Anti-Phase component

Out-of-Phase component

In-Phase component
(cross section)

Anti-Phase component
(cross section)

Out-of-Phase component
(cross section)

The sound pressure related decomposition of the cone movement shows a bending mode at 6 kHz that causes a dip in the frequency response. The inner and outer cone region vibrate in opposite phase and their produced volume flows cancel out each other.
There is a good bending moment propagation between the inner and outer cone due to the stiff honeycomb membrane which leads to this distinct vibration mode.