engleski

The correction of low frequency non-linearities due to non-optimal Qtc in loudspeakers by the use of negative feedback

Qtc is the total quality factor of the low frequency driver in a sealed box and it is determined by the total quality factor of the driver itself (Qts) and the volume of the enclosure that houses the driver. The most commonly used value of Qtc is 0.707, because it provides the flattest frequency response and the most acceptable rolloff of 12dB per octave, and it is achieved by adjusting the volume of the enclosure to the know Q of the chosen low-frequency driver. However, there are certain situations (due to space constraints, for instance) when the enclosure for the driver must be considerably reduced from its optimum size, leading to a significant increase of the loudspeaker’s resonance frequency, bumps in its frequency curve and a steeper rolloff. It is common practice that these unwelcome nonlinearities in the frequency response are partially compensated with the help of suitable equalizers. This article explores the possibility of using negative feedback to correct these nonlinearities in the frequency response of loudspeakers in sealed boxes of suboptimal volume and provides experimental results of the proposed method applied to a low-frequency driver in sealed boxes of different sizes.

loudspeaker; sealed box; Qtc; negative feedback; low-frequency nonlinearities

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