This multi-ply suspension owes its name to its resemblance to a spider web. Located around the core of the loudspeaker and attached to the bowl, it dampens considerably the movements. Its action is prolonged by the crown suspension of the membrane.
His vibrations make us the effect. This is the part of the speaker that we know best, as it is often apparent. It is most often in the form of a cone, or a dome or a ribbon for some speakers of medium or treble specific. The material chosen for its manufacture depends on the use of the loudspeaker. In the case of the subwoofer, petroleum derivatives are acclaimed, combined with rigid materials such as carbon or ceramics to stiffen the membrane and avoid deformations synonymous with distortion.
Integrated into the amplifier box, this electronic filter strongly attenuates the midrange and treble, so as not to disturb the operation of other speakers. In this case, we speak of a high-pass filter whose cutoff frequency is variable and determined by the user who can choose it by operating a potentiometer on the back of the box. Some boxes have a low-pass filter, also called a subsonic filter, which attenuates frequencies below 20 Hz so as not to damage the speaker.
To work, any speaker needs to be charged by a volume of air trapped in an enclosure. The woofer does not break this rule. The air volume of the subwoofer depends on the mechanical parameters of the speaker. This volume of air can be enclosed or tuned, that is to say opened on the outside through a resonator that takes over the speaker at its resonant frequency. This resonator can be a vent or a passive speaker.
The passive speaker
More and more popular, it works both as a resonator (vent) and as a virtual air volume, which allows to design very compact boxes. The passive speaker is devoid of magnet and coil and resonates at a specific frequency, taking over from the active speaker.