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Suspension Part Measurement (SPM)

Features and Benefits

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

The KLIPPEL SPM includes two modules for the measurement of medium and large size suspension parts (spiders, surrounds, cones). The SPM Lite is dedicated to the measurement of the mechanical stiffness k₀ and other parameters in the small signal domain. In addition, the SPM lite can be used to measure the linear parameters of passive radiators.
The SPM Pro is additionally capable of measuring the nonlinear stiffness K(x) and the reciprocal compliance C(x) versus displacement in the large signal domain over the full range of operation of the final product.

A dynamic, nondestructive technique according to the IEC standard IEC62459 is applied in order to measure the parts under similar dynamic conditions as operated in the loudspeaker. This guarantees 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 shape up to 222 mm diameter. The working bench pneumatically excites the device under test to vibrate at the clamped resonance. 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.

Specification

C2 SPM-Pro (nonlinear testing)
C7 SPM-Lite (small signal 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 or LST 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

in the small signal domain.

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 to the left 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.