Basics For Novices Dr.-Ing. Peter Strassacker

The components of a loudspeaker
A Loudspeaker consists of:

The cabinet
The cabinet should be extremely rigid and should not generate any resonance (unlike e.g. a violin). Suitable is particle board of 19 or 21 mm, that can be bought in most hardware stores. They even cut the boards to the required sizes (down to mm). For a first attempt in building a loudspeaker cabinet, building instructions of a kit should be used. The particle boards should be glued or screwed together, if required both. The cabinet has to be completely sealed.

Afterwards openings for the drivers, the terminal plate and a possible bass reflex port have to be cut out. For drawing a pair of composes should be used, the holes should be cut with a compass saw.

The drivers
The drivers convert electrical signals - coming from the amplifier - into mechanical waves that are audible as sound. Usually more than just one driver is needed for ensuring that the entire audible frequency range is represented. Low frequencies require large diameter diaphragm cones (short: diaphragms or cones), high frequencies require small diameter cones. Sometimes there is even a third driver with a medium diameter handling midrange frequencies.

The crossover
The purpose of the crossover is to divide and distribute frequency ranges to the individual drivers according to the their frequency capabilities. The high frequency driver (called: tweeter) cannot handle high power, low frequency sound while the low frequency driver (called: bass driver) cannot handle high frequencies.

The components of the crossover

The crossover receives electrical signals from the terminal. The terminal consists of (usually) two binding posts to which the two cables - coming from the amplifier - are connected.

The drivers receive the electrical signal from the crossover, usually by means of two cables. In the picture to the left the two circles represent the two terminals.

A crossover consists of:

The picture below shows the crossover of the PA 250 kit as an example:
Frequenzweiche PA 250
The characteristics of each component are described by its corresponding value.

The crossover described here is very simple and is taken from our PA 250 kit. It is e.g. used by a Swiss youth group for indoor and outdoor sound reproduction. At 250 Watt input this speaker achieves a sound pressure level of 120 dB (1 metre), almost exceeding the pain threshold. - This speaker is tuned for maximum sound level and can withstand short peaks of up to 1000 Watt.