High-quality sound speakers for home sound equipment to reproduce low-frequency signals with a frequency of 30-50 Hz, which corresponds to the length of the sound waves 7-10 m. in Order to efficiently radiate such fluctuations, we need a dynamic head with a large diameter of the diffuser (there are instances d of 400 mm). However, in practice most commonly used “dynamics” with the size from 200 to 300 mm. Their own resonant frequency in the range of 15-30 Hz.
When the head beep, her mobile system oscillates, radiating to both sides equal in strength but opposite phase sound waves, which are omnidirectional in nature. Body dynamics is not able to isolate one from another region of compression and rarefaction of the air. The result at the point of hearing sound pressure is low. This phenomenon is known in the art as an acoustic short circuit. Eliminate it by placing an acoustic radiator in a sealed box (Fig. 1). (Symbols in the figures denote: a — width B — depth C — height of the box, x is the material thickness, (1 — thickness of plate). Often it makes one or even several holes, positioning them in certain places of the body (Fig. 2). These holes are called patinir meters, or backreflection. Their kind — passive radiator (Fig. 3), which is an offline dynamic head. The location of the holes on the front panel speakers are selected in such a way that back radiation coincided with the front, thereby increasing the low frequency sound pressure.
Important for speakers, have their size, shape and materials from which they are made, the internal “stuffing” and design of the front panel. Thus, the body affects the technical parameters established in this dynamic heads and primarily on enhancing its own resonant frequency. An important role is played by the diameter of the diffuser and “displacement” hull. With the increase and decrease in the size of the moving system resonance frequency varies slightly. If the head with a large diffuser to install in a relatively small box, the resonance frequency will change markedly — low frequency “cut off”, and as a result the effective frequency range of speakers is shrinking. In other words, incorrectly matched by the volume of the housing can degrade the playback quality even very good drivers.