Ole Wolff Elektronik A/S, Roedengvej 14, 4180 Soroe
sales@owolff.com, T: +45 5783 3830
21-09-2021

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Diaphragm design

Using advanced simulation and measurement tools


Optimizing diaphragm behavior through simulations and measurements


The diaphragm (or membrane) of the speaker/driver is what transforms the alternating magnetic field generated in the voice coil into the pressure variations known as “sound”. In most cases, the ideal diaphragm should convert the applied voltage into piston-like movements regardless of frequency and amplitude. This is no easy task since phenomena like breakups and rocking modes, material nonlinearities etc. occur in the real world. Being able to predict and measure these imperfections can speed up a design process significantly.


No more shooting in the dark

Previously diaphragm design relied on “cut-and-try” approach based on many years of experience of do’s and don’ts. This method is very time- and cost ineffective and even if huge resources are invested, there is no guarantee that the optimal design and performance has been reached. At Ole Wolff we have a faster and more reliable way of designing and optimizing diaphragms.

COMSOL Multiphysics® allow us to design diaphragms for various sizes of transducers where parameters such as foil type (single or multi layers), thicknesses of the foils, geometry of suspension, piston area and shape, number of stabilizing grooves in the diaphragm surface etc. can be simulated and performance verified before any mechanical tooling process is entered. This combined with years of experience assures shortest lead time and closest match to performance targets.

The Klippel Scanning Vibrometer System (SCN) enables us to measure and visualize the diaphragm behavior and adjust and derive material parameters for the Comsol model for further optimization.


Read more about Transducer design


Klippel Scanning Vibrometer System (SCN)

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State-of-the-art technology allows Ole Wolff to:

  • Measure geometry and mechanical vibration of the transducer
  • Visualize the vibration behavior
  • Show contribution to sound pressure output
  • Predict directivity pattern
  • Separate radial and circular modes
  • Analyze actively radiating cone regions
  • Detect loudspeaker defect


Near Field Add-On

Ole Wolff also has the SCN-NF which adds 2pi acoustical measurement capabilities to the same Scanning Vibrometer platform used for laser scan diaphragm vibration.

The SCN hardware is extended with a microphone in addition to the existing laser sensor.

Automated axis control ensures repeatable, precise and fast positioning of the microphone and laser sensors, in combination with a round baffle for measuring transducers up to 10" (30 cm) in diameter, or compact (smart) speakers.

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The SCN Analysis Software performs visualization, animation and analysis of the mechanical vibration using the scanned data which is provided by the vibrometer.

The sound pressure output at any point in the half-space sound field and the polar radiation characteristic are predicted by using mechanical data. Novel decomposition techniques show radial and circular modes and vibration components related to the SPL output.

It is the target of the analysis to provide a better understanding of the interaction between vibration and radiation. Deepened analytics can be provided by optional modules for modal analysis of rocking modes and higher order modes.


Read more about Transducer design


Simulations


Knowing the material properties and having an accurate CAD, the diaphragm behavior can be predicted in Comsol Multiphysics®. Typically the model is set up using a combination of pressure acoustics, solid mechanics, shell physics and lumped electrical/magnetic parameters.


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Full vibro-acoustic simulation of conceptual Ole Wolff headphone driver. The animation shows the deformation of the diaphragm at 1875Hz. The deformation is highly exaggerated for the purpose of visualization.


Read more about simulation in Comsol Multiphysics®


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Comsol simulation of mode at 1875 Hz shows great agreement with Klippel measurement
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Mode at 1875 Hz measured with Klippel SCN system
hvid Streg

contact Ole wolff acoustic design mangeticsDo you want to know more about Diaphragm Design?

Involve Ole Wolff early in your design process and you will get the best result.
Send an e-mail or contact your local sales contact to learn what Ole Wolff can do to help developing your products.


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