Speaker (Bass-reflex)
A bass-reflex box is an open box. Includes an opening that allows air to flow from inside to outside of the box. This opening is often practiced in front of the camera and generally in a circular. Usually include a tube whose dimensions conform to cushion the overall ventilation speaker to get the desired frequency response.
The principle of the bass reflex is: All the box is a ventilation system that includes an acoustic resonance. The air in the vent pipe is a mass of inertia. The air in the chamber is suspended like a spring. These two elements are physically connected and have a resonance at a particular frequency. This resonance is opposed to the movement of the diaphragm of the speaker to a very precise frequency.
The advantage of a Hi-Fi speaker of ventilation is that the displacement of the membrane is less important. This helps reduce intermodulation distortion. It is also easier to obtain a low frequency response. On the contrary, this type of camera is more difficult to achieve, their size and the ventilation tube should be accurately determined according to the characteristics of the speakers.
Advantages of the close box |
Disadvantages of the close box |
The quality of the speaker is relatively less sensitive in close support, and we may also use a loudspeaker diameter lower (25 instead of 30 cm or 30 instead of 38 cm) for theoretical results identical. |
The principle of the vent leads to a phenomenon of lag and noise airflow, which is not negligible. |
The total volume of the box is lower than an office close, always equivalent results. With a large speaker and vent properly calculated, we can drop very low in the extreme bass. |
The principle Bass reflex may cause sudden heels (up to the destruction of the speaker) when using the speaker beyond its capacity in power or if it sends too serious frequencies (below the resonant frequency of the vent). Beware of bass-reflex using loudspeakers poor quality ... They move much air, but does not reproduce in infra-serious. |
Finally the performance of such a cabinet is pretty much superior to that of a closed box, hence the need for electrical power than for the same sound pressure provided. |
The fund may be insufficiently rigid, resulting in a permanent phenomenon of "boom boom" very uncomfortable (especially in High Fidelity). |
MONTAGE DES BOOMERS EN ENCEINTE BASS-REFLEX
In the bass-reflex enclosure, a vent is used in the resonator
auxiliary.
The resonant frequency of the vent is written:
For good results at low frequencies:
- The resonant frequency of the vent must be equal to the
resonant frequency in the open air speaker;
- The surface of the vent must be below the surface
Speaker divided by twenty.