Suspension part

• Woofer
• Other Transducers

Spider and surrounds are critical parts of the mechanical system determining the total stiffness of the suspension and centering the rest position of the voice coil in the gap. The shape of the stiffness nonlinearity causes nonlinear distortion and limits the maximal peak displacement. The asymmetrical shape of the curve may rectify the ac signal causing a dc component in the voice coil displacement which moves the coil away from the rest position. Visco-elastic properties of the suspension material may cause a memory effect of the suspension, such as creeping of the displacement, loss of stiffness for low frequencies and after high peak displacement. 
Therefore, the static, quasi-static and point-by-point (incremental) methods provide data which cannot describe the dynamic behavior of the suspension at audio frequencies. Reliable data require a dynamic operation above 10 Hz in vertical orientation while the inner and outer rim of the suspension part is clamped in a similar way as used in the final application. The properties of the suspension part highly depend on temperature, humidity and vary over time.

• High peak displacement for small size
• Symmetrical shape of the stiffness characteristic versus positive and negative excursion
• Desired soft limiting to protect the voice coil former
• Stiffness K(x=0) at rest position is constant over time (ageing)
• Stiffness K(x=0) at rest position is independent from peak displacement xpeak
• Suspension characteristics are independent on climate conditions

• Stiffness K(x=0) at rest position
• Shape of the stiffness characteristic K(x)
• Force-deflection curve F(x)

• Asymmetrical shape of the K(x) characteristic generates dc displacement which moves the coil away from optimal rest position and generates Bl intermodulation distortion
• Stiffness K(x=0) at rest position decreases over time and may cause motor instability

• Laser
• Microphone
• SPM Bench 
• MSPM Bench

Speaker Component Measurement with KLIPPEL