IEC PAS-62458:2006 pdf download Sound system equipment – Electroacoustical transducers – Measurement of large signal parameters
3.7 compliance limited displacement x C
displacement implicitly defined by minimal compliance ratio which is the ratio of the minimal value of the force factor, C(x), in the working range ±x C referred to the C value at the rest position x = 0. After defining the threshold C min the displacement limit, x C , can be found in the non-linear C(x) characteristic
3.8 excursion
limit, x limit limit describing the maximal travel of the coil without considering the distortion in the output signal. This value may be derived from the geometry of the moving coil assembly and the suspension but should be verified by practical testing to ensure that the loudspeaker can be operated up to x limit without being damaged 3.9 static method measurement technique which determines the non-linear parameters of the transducer by using a d.c. signal of certain magnitude U i (for example, voltage) as stimulus. To measure the non-linear parameters within the working range –x peak < x i < x peak with sufficient resolution, multiple measurements are performed where the magnitude of the d.c. stimulus is changed (for example, voltage U i = i × U step with I = 1,… N). At each working point, i, the displacement, x i, and other relevant state variables (force F i , current i i ) are measured after the transducer has reached steady state. Due to the visco-elastic behaviour of the suspension material, the settling time may exceed multiple seconds. The values K(x i ), Bl(x i ) and L e (x i ) at the working point, x i, are estimated by using equations (1), (3) and (4) 3.10 point-by-point dynamic method measurement technique which determines the non-linear parameters of the transducer by using a d.c. signal, U i (for example, voltage), superimposed with a small a.c. signal, U ac , as stimulus. To measure the non-linear parameters within the working range –x peak < x i < x peak with sufficient resolution, multiple measurements are performed where the magnitude of the d.c. stimulus is changed (for example, voltage U i = i × U step with i = 1,… N). At each working point, i, the d.c. displacement, x i , and other relevant d.c. and a.c. state variables (a.c. part of the displacement, x ac , force, F ac , current, i ac ) are measured after the transducer has reached steady state. Due to the visco-elastic behaviour of the suspension material, the settling time may be multiple seconds. The amplitude of the a.c. stimulus is sufficiently small to ensure that the transducer behaves linearly (K(x i +x ac ) ≈ const., Bl(x i +x ac ) ≈ const. and L e (x i +x ac ) ≈ const.). The parameters of a linear loudspeaker model are estimated at the particular working point, x i , by using the measured a.c. state variables only. Whereas some small signal parameters (force factor Bl(x i ) and inductance L e (x i ) are identical to the large signal parameters measured by other methods, this technique provides the incremental stiffness, K inc (x i ), which has to be transformed into the regular stiffness by integration