The generation of a sound and its radiation are two separate processes. In the case of loudspeakers, the loudspeaker principle determines the sound or sound generation; the design of the loudspeaker determines the transmission of the sound pressure. The sound volume and the frequency range of a loudspeaker, however, only become fully effective in connection with the sound radiation. This function is performed by baffles, loudspeaker boxes and bass reflex boxes.
Structure of a loudspeaker box
Loudspeaker boxes are smaller or larger wooden cabinets with one or more loudspeakers at the front for sound radiation. The cabinet prevents acoustic short circuits that work against the movement of the membrane. This allows the speaker membrane to release its kinetic energy into the air. Loudspeaker cabinets are lined with damping material to prevent the formation of natural resonances and, depending on the concept, are designed as self-contained loudspeaker cabinets or have an air vent at the front or rear.
Speaker boxes that radiate the complete frequency range are equipped with two, three or four speakers: with midrange drivers( MT), combined with tweeters( HT) and woofers(TT). In this context, one speaks of multi-way systems. Depending on the concept, a distinction is made between 1-, 2-, 3- or 4-way systems, with the paths referring to the frequency ranges. For example, a 3-way speaker system consists of a midrange driver, tweeter and woofer. The connections of the various chassis are led to the outside and can be connected with a speaker cable or in bi-wiring, bi-amping or tri-wiring, depending on the connection concept.
Self-contained loudspeaker cabinets form an infinitely large baffle where the radiated sound cannot reach the back of the loudspeaker. The air enclosed in the cabinet forms an air cushion with a defined spring stiffness. In the low frequency range, the efficiency is relatively low. Loudspeakers with quality factors with Qts values of more than 0.5 can be used in speaker cabinets. The Qts value determines the damping behavior of the loudspeaker and is decisive for its transient response.
The different multi-way systems
The 1-way system uses a full-range loudspeaker whose frequency response covers the entire audio range from low to high frequencies. The reproduction of high frequencies is critical in the 1-way system, which works without crossovers.
The 2-way system consists of a mid-bass and a tweeter. Both speakers can be connected via crossovers, whereby the crossover frequency is 2 kHz to 3 kHz.
The 3-way system consists of three speakers: a tweeter, midrange and woofer. There are various degrees of freedom for the lower and upper crossover frequency. In addition, design options with other speakers. The loudspeakers are controlled separately via crossovers.
The multi-way systems have sufficient design freedom and are not explicitly classified. For example, a 4-way system can use a tweeter, a woofer and two midrange drivers. One of the better known arrangement systems is the D'Appolito arrangement.
If the loudspeaker box contains one or more power amplifiers, it is called an active box; if the loudspeakers are driven by an external power amplifier, they are passive boxes.