Alignment
Coupling between two resonant systems of one degree of freedom (loudspeaker + Helmholtz resonator) creates a two degrees of freedom system with two resonances. In fact, the pressure response, proportional to the volume velocity response
, is a response of order 4 which is written in general terms as:
where
, noting
.
Pressure response is therefore a high-pass filter of order 4 having a slope of 24 dB/oct.
So, it is necessary to choose the dimensions of a Helmholtz resonator in such a way that the volume velocity generated by the vent is neither too large nor too small to obtain a suitable response at low frequencies, that is to say not showing any too visible resonance, which caused dragging effects in the vicinity of the resonant frequency of the box.
