.D'ailleurs j'extrais la phrase qui va bien :
At first glance, the port output seems to be 3 to 5 dB higher than the woofer output, which is a counter intuitive result. This is due to the diameter difference between the woofer and port. The port output can be scaled to the correct relative level by writing the summing equation in a different form:
pTOT = pWOOFER + DPORT/DWOOFER * PPORT [5]
For this example, the woofer effective diameter is 14 cm and the port diameter is 5.5 cm, which gives:
DPORT / DWOOFER = 5.5/14 = 0.39 = −8.1 dB [6]
The scaled version of the port response is also plotted in Figure 4a. Now you can see that it is more in line with the woofer level. Before leaving Figure 4a, there are two interesting points not directly related to near-field testing. First, the sharp dip in woofer response at 37.6 Hz indicates the tuning frequency of the vented enclosure. In general, this value is more accurate than one obtained from the impedance curve, since it is not corrupted by voice coil inductance.
