• Technology
• + Voice Coil Impedance
• Introduction
• Glossary
• Lumped Impedance Modelling
• Measurement
• Fem Modelling
• Prediction of Distortion
• Conclusion
• Download as PDF
• + Surround Sound with Fewer Speakers
• Introduction
• Sound Quality Objectivies
• Creating Virtual Soundfields
• Practical systems
• Conclusion
• + Optimum Diapragm Waveguide Geometry
• Introduction
• Sperical Waves
• Analysis Stategy
• Results
• Discussion
• Conclusion
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•   Pod Technology
• + Uni-Q White Paper
• Introduction
• Background
• Co-Axial Drivers
• Co-Incident Drivers
• Magnetic Design
• Acoustics
• Discussion
• Conclusion
• References
• Full Paper (PDF)
• + High End Uni-Q
• Coincident Source Array
• Finite Element Analysis
• Dome Profile
• Wavefront Analysis
• Motor Systems
• Laser Vibrometry
• References
• + Reference Paper
• Introduction
• Research & Development
• Reference 207
• Production
• System Design
• Boundary Control Device
• + ACE Technology
• Introduction
• How Does ACE Work?
• Adsorption
• Improvements
• Performance
• Applications
• Technology
• References
• Full Paper (PDF)

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Finite Element Analysis

There are two ways to model loudspeaker behaviour: with lumped parameters or with distributed parameters. Lumped-parameter modelling has been in use for several decades and provides a quick, simple analysis which is usually fairly accurate at low frequencies [1]. However, as frequency increases the reliability of this method fails. At frequencies where the loudspeaker cannot be treated as a lumped-parameter system, the distributed-parameter approach must be used. One popular version is Finite Element Analysis (FEA). KEF were early adopters of the technique for loudspeaker design and have recently integrated it into the design methodology such that it has become a routine design tool [6]. Already significant productivity benefits are apparent.

Essentially the process by which FEA works is to subdivide a complex system into a very large number of simple but interdependent subsystems (finite elements).

If FEA is used to model a structural system (such as a loudspeaker diaphragm) these subsystems will have mass, stiffness and damping properties - and mathematical formulae - which define their behaviour. Because the behaviour of each element is affected by all the others to which it is directly or indirectly connected, the only way the behaviour of the entire system can be analysed is to derive a very large number of simultaneous equations and solve them using matrix mathematics - something to which computers are ideally suited.

KEF use Finite Element Analysis in two distinct forms: (1) for electromagnetic (motor) designs, and (2) for mechano-acoustical (or vibroacoustic) design of the vibrating and radiating parts of the loudspeaker. In theory these two parts could be modelled simultaneously but FEA is computationally intensive and, at present, it is more productive to divide the design and computational effort into two areas.

Magnetic FEA allowed KEF Engineers to optimise the magnet circuits for all the new drivers in the Reference 207, including the radical ‘series neodymium’ approach of the Uni-Q array.

Magnetic FEA can also lead to significant weight reduction, either by using lightweight neodymium instead of conventional ferrites for the permanent magnet or even by optimising geometry and removing significant volumes of redundant metal and thereby reducing distortion.

Vibroacoustic FEA has just reached maturity with its contribution to the design of the KEF Reference 207. It is no exaggeration to state that without FEA it would not be possible to design such a high-performance loudspeaker in such a short period of time.

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