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Scanning Mechanical Vibration


Complex transfer function Hx(r, f) at point r on the radiator’s surfaceTRF, SCN
Magnitude and phase plotSCN
Animated vibration patternSCN, RMA, HMA
Distributed mechanical parameters SCN, RMA, HMA
Rocking mode SCN, RMA

The complex transfer function between electrical input and mechanical vibration measured at multiple points r with sufficient spatial resolution on the surface of the radiator may be considered as distributed parameters describing the vibration behaviour of the transducer in the small signal domain. The data can be represented as magnitude and phase response at a particular point, as a distribution of magnitude and phase over the surface, and as a 2D or 3D animation where the vibration is superimposed with the geometry of the radiator.



Transfer Function Measurement (TRF)

Using a sweep with amplitude shaping (emphasis by 10 dB/octave to higher frequencies), TRF measures the displacement transfer function Hx(f) at higher frequencies (25 kHz) with sufficient SNR.

Scanning Vibrometer System (SCN)

SCN uses TRF, DA hardware, laser and additional control robotics (two linear actuators and a turntable) to scan the mechanical vibration and geometry.

Rocking Mode Analysis (RMA)

Uses laser scanner vibrometer measurements of transducers for automatic identification of the root-causes of rocking modes. Quantifies imbalances of mass, stiffness and force factor and reveals the location of each imbalance center on the diaphragm. This is useful in avoiding driver instability, voice-coil rubbing and impulsive distortion and in assuring consistency of production. Especially suited for microspeakers and headphone transducers.

Higher Modal Analysis (HMA)

Uses laser scanner measurement for automatic identification of modal parameters (modal resonance frequency, damping, gain) and characteristic vibration patterns (mode shapes). This divides the complicated vibration pattern on the diaphragm into separate vibration components that are easier to interpret. Interaction of modes and their influence on sound radiation and response can be studied and non-beneficial vibration-patterns identified. Modal parameters can be used to tune finite element models which share the same “modal view”. The module provides animated view of diaphragm deformation to locate potential sources of nonlinear distortion.


The figure above shows different ways how to visualize the transfer function describing the vibration of the scanned surface.
The figure above shows different ways how to visualize the transfer function describing the vibration of the scanned surface.

Templates of KLIPPEL Products

TRF Scanning Cone Vibration
Manual scanning of cone vibration using a laser sensor with high cut-off frequency (>15 kHz)


Audio Engineering Society 
AES2 Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement 

International Electrotechnical Commission 
IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers

Papers and Preprints

W. Klippel, et al., “Distributed Mechanical Parameters of Loudspeakers Part 1: Measurement,” J. of Audio Eng. Soc. 57, No. 9, pp. 500-511 (2009 Sept.).

W. Klippel, et al., “Distributed Mechanical Parameters of Loudspeakers Part 2: Diagnostics,” J. of Audio Eng. Soc. 57, No. 9, pp. 696-708 (2009 Sept.).

F. J. M. Frankort, “Vibration Patterns and Radiation Behavior of Loudspeaker Cones,” J. of Audio Eng. Soc., Volume 26, No. 9, pp. 609-622 (September 1978).

J. R. Wright, “Automatic Vibration Analysis by Laser Interferometry,” presented at the 88th Convention of the Audio Eng. Soc., Preprint 2889, (March 1990).

C. Struck, “Analysis of the Nonrigid Behavior of a Loudspeaker Diaphragm using Modal Analysis,” presented at 86th convention of Audio Eng. Soc., Hamburg, Preprint 2779 (1989).

P. J. Anthony, et al., “Finite-Element Analysis in the Design of High-Quality Loudspeakers,” presented at the 108th Convention of the Audio Eng. Soc., February 2000, Preprint 5162.

M. Karjalainen, et al., “Comparison of Numerical Simulation Models and Measured Low-Frequency Behavior of a Loudspeaker,” presented at the 104th Convention of the Audio Eng. Soc., May 1998, Preprint 4722.

J. Wright, “Finite Element Analysis as a Loudspeaker Design Tool,” Paper MAL-11; Conference: AES UK Conference: Microphones & Loudspeakers, The Ins & Outs of Audio (MAL), March 1998.

A. Bright, “Vibration Behaviour of Single-Suspension Electrodynamic Loudspeakers,” presented at the 109th Convention of the Audio Eng. Soc., (September 2000), Preprint 5213.

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