Enclosure type
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Closed box. The simplest type of case: a box closed on all sides with a speaker (speakers) on the front panel. The advantages of such models are high accuracy of sound transmission and low cost, the disadvantages are low sensitivity and somewhat “flat” bass.
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Phase inverter. A classic phase inverter is a hollow tube connecting the internal volume of the case with the outside world (however, there are other options for such a connection). The length of the phase inverter channel is chosen so that the sound waves of a certain range, passing through it, are inverted in phase relative to the waves from the speaker (hence the name). This improves (in particular, "deepens") the sound of the subwoofer and allows you to achieve good performance with a small cabinet size. On the other hand, the sound stream in the tube creates a certain additional noise.
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Strip. A design that combines the features of a closed box and a bass-reflex enclosure. One of its parts is made closed, and the second is equipped with a phase inverter tube; between them is a partition, on which the main speaker is located. Unlike previous types, the speaker is entirely inside the case. Strip-line enclosures provide louder sound than boxes or bass reflexes, with sound quality comparable to the latter. The disadvantage is the complexity of the design, as a result — a slightly higher price.
Body shape
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Case Box. Literally "box". The simplest type of case, in fact, is a box of medium dimensions, designed for installation in the boot.
— Compact. This option means rather than the shape, but the size of the case — as the name implies, it includes devices that have small dimensions. Such subwoofers are as simple as possible to install, some models can be installed directly
under the seat. At the same time, their sound quality and power are usually lower than those of full-size ones.
— Tube. The case is in the form of a pipe, on one of the ends of which a speaker is displayed. This form does not significantly affect the sound characteristics, it plays mainly an aesthetic role —
subwoofers-pipes look quite stylish.
Rated power
The average (root mean square — RMS) power of the input signal, at which the subwoofer is able to work continuously without negative consequences (damage, failure) for at least an hour. The rated power of the subwoofer must be greater than the power of the amplifier connected to it — in order to avoid overloads.
Max. power
The maximum signal power that the subwoofer is able to withstand for a short time (up to several seconds) without any negative consequences. When selecting an amplifier-subwoofer pair, it is recommended to take a subwoofer with a maximum power of at least twice the maximum power of the amplifier. In general, the higher the maximum power, the more resistant the subwoofer is to overloads.
Resonant frequency
The natural frequency of the cone in the subwoofer speaker, namely the frequency with which the cone will oscillate if the speaker is suspended freely in the air and a single impulse is transmitted to the cone (for example, by clicking on it with your finger). In subwoofers, this parameter determines, in particular, the lower limit of the frequency range (see above): at frequencies below the resonant sound power drops sharply. Accordingly, for deep rich bass, the resonant frequency should be as low as possible. This parameter is also used to calculate the size of the enclosure for the subwoofer.
