Woofer is commonly known for its loudspeaker driver, designed to produce low frequency sounds. It can produce sounds ranging from around 40 hertz up to about a kilohertz or even higher. The name is derived from a dog bark, woof in contrast with tweeter. It is a name given to the speakers designed to reproduce high frequency sounds.



The most common design of a woofer is the electrodynamic driver. These use a cone, driven by a voice coil surrounded by a magnetic field. The combination of both the voice coil and the magnet forms a linear electric motor.

And when current flows through the voice coil, the coil then moves in relation to the frame, causing the coil to push or pull on the driver cone in a piston like way. The voice coil is attached to the back of the speaker cone with the help of an adhesive. The resulting motion of the cone creates sound waves as it moves in and out.

Designing and manufacturing a woofer is a challenging task. While designing a woofer you have to keep in mind the following points. Controlling the motion of the cone so the electrical signal to the woofer voice coil is dependably reproduced by the sound waves produced by the cone motion. Controlling the electrical impedance, which is the measure of opposition to a sinusoidal alternating current, is a challenging task. This is done so that the use of economic electronic amplifier can be made possible.

A good woofer design requires an effective conversion of low frequency amplifier signal to mechanical air movement with high commitment and maximum efficiency. It is complicated with the necessity of using a loudspeaker enclosure to couple the cone motion to the air.

The cone materials have its advantages and disadvantages. The three common high quality properties that designers look for in cones are light weight, stiffness and lack of coloration. Exotic materials like Kevlar and magnesium are light and stiff, but they can have ringing problems, depending on their fabrication and design. Materials like paper, which also includes the coated paper cones, and various other polymers will generally ring less than metal diaphragms, but can be heavier and not as stiff.

But, how the frame is design? The frame or the basket is the structure, which holds the cone, voice coil and the magnet in the power alignment. The voice coil gap is quite narrow, therefore it is important to prevent rubbing of the voice coil against the magnet structure in the gap and also to avoid extraneous motions.

There are two types of metal frames that are stamped and cast. Stamped baskets usually made of steel is a lower cost option. And the disadvantage of this frame is that the basket may bend if the speakers are on higher volumes. Cast baskets are more expensive but they are more rigid in all directions. Cast baskets have better damping, can have more intricate shapes, and are therefore usually the preferred for higher quality. Woofers designed for public address and instrument applications are similar to that of the structure of a home audio woofer.