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Rocking Mode Analysis (RMA)

Features and Benefits

Cope with rub&buzz
Optimize speaker stability
Find the dominant root cause
Capture imbalances in mass, stiffness, BI
Locate imbalances on the diaphragm
Detects systematic errors
Fast laser scan <15 min

For microspeakers, headphone drivers and other transducer designs with thin build and simple suspensions, rocking modes are a common problem. These undesired tilting resonances of the diaphragm appear often in the low end of the passband where they affect the stability of the driver during bass reproduction: Due to the very low damping of rocking modes, already tiny inhomogeneities in the design can trigger large tilting angles, which can force the voice coil to hit the boundaries of the magnetic gap. This will dramatically reduce life-time of the speaker and deteriorate the allowable output and perceived quality of the product due to excessive impulsive distortion.

The Rocking Mode Analysis (RMA) is designed to provide the necessary diagnostics to solve such problems. Using distributed vibration data measured by laser vibrometry (Klippel Laser Scanner System (SCN) or Polytec LDV through POLY2SCN ), it separates the undesired rocking modes from the desired piston mode.

RMA identifies the root-causes for the rocking: Imbalances in the distributions of mass, stiffness and electromagnetic force factor. It quantifies their excitation forces, ranks them in order of magnitude and shows where the geometrical center for each of these imbalances is located on the diaphragm. With this information available, weak points in the design and in the manufacturing, process can be unveiled with great benefits for the performance and reliability of the speaker.