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Suspension Part Measurement (SPM)

Features and Benefits

Specification of suspension parts
Analysis of cause of distortion
Defining mechanical limits
Quality control in manufacturing
Optimal driver design in R&D

The nonlinear stiffness K(x) and the reciprocal compliance C(x) of suspension parts (spider, surrounds, cones) and passive radiators (drones) are measured versus displacement x over the full range of the operation. A dynamic, nondestructive technique according to the IEC standard IEC62459 is developed which measures the parts under similar conditions as operated in the loudspeaker. This guarantees the highest precision of the results as well as a simple handling and a short measurement time. Suspension parts are fixed in the measurement bench by using a set of clamping parts (rings, cones, cups) fitting to any size of circular geometries up to 222 mm diameter. The working bench excites pneumatically the suspension to vibration at the resonance frequency related to the stiffness and the mass of the suspension and inner clamping parts. The measured parameter is required for specifying the large signal properties of the suspension parts and to detect asymmetrical and symmetrical variation which are the cause for instable vibration behavior and nonlinear distortion.

Advantages

Dynamical method
Vertical operation
Robust, easy to use

Specification

C2 SPM-Pro nonlinear testing
C7 SPM-Lite linear testing
Module Overview - Moving Parts Measurement

Standard measurements

Transducer nonlinearities (curve shape)
Single-valued nonlinear parameters

Requirements

Hardware
• Klippel Analyzer 3 (KA3)

Software
• dB-Lab
• SPM software

Module
• Transfer Function Measurement (TRF):
Measurement of transfer function and harmonic distortion

Accessories
• SPM bench
• Clamping set (ring, cone, cup)
• Laser
• Amplifier
• PC

Demo Video (Introduction)

SPM Lite and Pro

SPM Lite

Measurement of resonance frequency, Q-factor and identification of linear parameters

Stiffness
Moving mass
Mechanical resistance R

SPM Pro

In contrast to the linear model, the stiffness of a real suspension is not constant but varies with displacement x. Thus, the stiffness K(x) versus displacement reveals the nonlinearity of the suspension part. The SPM Pro measurement automatically determines the voltage and frequency of the excitation signal to measure the nonlinear stiffness at a specified target displacement. An additional long-term measurement mode allows to track changes of the nonlinear stiffness over a long excitation time.

Example

The figure above shows the variation of the nonlinear stiffness versus time using the SPM module in the long-term measurement mode. While the suspension part is permanently excited at the target displacement (15 mm peak), the nonlinear stiffness is measured in 15 minute intervals.