Claus Futtrup

DALI A/S · Research and Development

A numerical method to compute the time-domain response of a loudspeaker or other transducer using contour integration of its frequency response (i.e., transfer function) is presented. The approach, based on Weideman's scheme for inversion of the Laplace transform along a parabolic contour, is applicable to analytic functions that contain isolated s...

We present a methodology to measure transducers with a dual-added-mass technique in order to extract the motional impedance ZM(ω) and force factor Bℓ from the total impedance. This methodology is suitable for determining moving mass and compliance for motional impedance models that include viscoelasticity and frequency-dependent damping by curve fi...

Previous papers dealt with a lumped parameter model for the dynamic loudspeaker which incorporates a mechanical resistance proportional to frequency taking into account the frequency dependence of the mechanical damping. In the present paper, the model is further refined to include frequency dependence of compliance based on the so-called "LOG mode...

An equivalent circuit model for dynamic moving-coil transducers incorporating a semiinductance had been evaluated previously. A more complex equivalent circuit model inspired by problems with loudspeakers with a copper cap on the pole piece is now evaluated in order to include transducers that were not covered by the previous model. A simplified ve...

In recent papers, a lumped parameter model, which can simulate the impedance of conventional electro-dynamic transducers accurately, has been presented. The new model includes frequency-dependent damping, which questions traditional engineering practices in simulations of loudspeaker enclosures and, in particular, associated losses. In this paper,...

The viscoelastic effects in loudspeaker suspensions are investigated from a theoretical point of view as well as via measurements of the electrical impedance and velocity for two loudspeakers, one with high-loss, the other with low-loss surround. As the viscoelastic effects lead to frequency dependence of damping and compliance, better parameter es...

Conventional subwoofers are usually quite deep to accommodate long throw. A shallow subwoofer (SSW) design is presented which aims to maintain the quality of low distortion and long throw bass reproduction. Two design concepts, applicable to larger drivers, are described and results are shown. The result is more bass for a given speaker-depth witho...