Loudspeaker

Abstract

Sound emanating from the high-frequency diaphragm of a coaxial speaker will diffract into the annular gap between the tweeter unit and the midrange cone. This results in response irregularities. We therefore disclose a loudspeaker, comprising first and second drivers located substantially coaxially with the first driver located centrally and the second driver located concentrically around the first driver, the loudspeaker being bounded at its radially outer side for at least part of its extent by the voice coil former of the second driver and including a spacing between the outermost extent of the first driver and the innermost extent of the second driver thus defining an annular space, the annular space containing a sound-absorbent material. By placing the sound-absorbing material in the annular space, the resonances within this space are damped, thus alleviating their effect. The annular space can have a lower resonant frequency that is below the passband of the first driver. Essentially, instead of minimising the effect of the annular gap by reducing its size and seeking to seal its outer opening, we propose to enlarge the space so that the fundamental resonant frequency it exhibits drops out of the passband of the high-frequency driver and hence out of the frequency range of interest. This both prevents the fundamental frequency of the cavity from being excited, and also allows sufficient room within the space to accommodate a sound-absorbent material to absorb these undesirable resonances.