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 limit 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 forcing the voice coil to hit the boundaries of the magnetic gap. Rubbing of the coil will dramatically reduce life-time of the speaker and deteriorate the 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 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 imbalances in the distribution of mass, stiffness and force factor in the electro-mechanical system. It then quantifies the contribution of each root cause to the total rocking motion and reveals the position of the center of imbalance for mass, stiffness and excitation force on the diaphragm. With this information available, weak points in the design can be found and problems in manufacturing solved. The risk of voice coil rubbing and impulsive distortion in the output signal is effectively reduced with great benefits for the quality and reliability of the speaker.