Supervision: Thomas Laurence

Project type: Semester project (bachelor) Semester project (master) Master thesis

Finished

The electrodynamic moving-coil loudspeaker, as patented by Kellogg and Rice in 1924, is the most spread electroacoustic diffuser in the audio industry, since the 1920's. Historically, the current geometry has been imposed by sound performances constraints, following the earlier "ribbon loudspeaker", which was composed a flat and wide electric sheet surrounded by 2 permanent magnets of opposite polarities. However, despite the interesting acoustic radiation performances achieved with conventional moving-coil loudspeakers, there are several situations where a flat, symmetric, electroacoustic transduction should be favoured. This is particularly the case when we want to use the loudspeaker diaphragm as an active acoustic resonator, eg. inside an acoustic waveguide, so as to change the transmission characteristics of a transmission-line unit-cell.

The aim of this project is to identify a convenient "flat" and "symmetric" electrodynamic loudspeaker design, based on the principle of the "isodynamic" loudspeaker. This transducer resembles a ribbon loudspeaker, where the electric cicruit is printed on a thin vibrating film (eg Kapton) the magnet being placed on the surround of the membrane rather than obstructing the back side of the loudspeaker. It is expected to be used as a relatively small membrane (around 5 cm diameter) for active acoustic impedance control applications.

The project will consist in:

• identifying good geometries to achieve correct electroacoustic transduction with the chosen principle

• optimise the electroacoustic performance on a simulation software

• design and build a prototype

• assess the prototype performance

**Profile: ** Electrical engineering, Micro-engineering

**Prerequisites: ** Electroacoustique (BA5) or Audio Engineering (MA1)

**Context: ** Theory (40%), design (40%), measurement (20%)