Dayton Audio PS180-8 6-1 - Manual (Page 6)

The displacement limits XBL, XC, XL and Xd describe the limiting effect for the force factor Bl(x), compliance Cms(x), inductance
Le(x) and Doppler effect, respectively, according to the threshold values Blmin, Cmin, Z-max and d2 used. The thresholds
Blmin= 82 %, Cmin=75 %, Z-max=10 % and d2=10% generate for a two-tone-signal (f1=fs, f2=8.5fs) 10 % total harmonic
distortion and 10 % intermodulation distortion. The thresholds Blmin= 70 %, Cmin=50 %, Z-max=17 % create 20 % total
harmonic distortion which is becoming the standard for acceptable subwoofer distortion thresholds.
Traditionally, Xmax has been defined as the physical overhang of the voice coil, 15% times the physical overhang, or the
point where BL has dropped 70% from its X=0 value (same as X Bl). The additional nonlinear limits allow us to quantify the
other factors that limit a loudspeaker’s performance.
These parameters are defined in more detail in the papers: “ AN04 – Measurement of Peak Displacement Xmax” , “ AN05
- Displacement Limits due to Driver Nonlinearities.” , “AN17 - Credibility of Nonlinear Parameters” , “ Prediction of
Speaker Performance at High Amplitudes” , “Assessment of Voice Coil Peak Displacement Xmax” , and “Assessing Large
Signal Performance of Loudspeakers”
Symbol Number Unit Comment
Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=70% 4.6 mm Displacement limit due to force factor variation
X C @ C min=50% 4.5 mm Displacement limit due to compliance variation
X L @ Z max=10 % >4.9 mm Displacement limit due to inductance variation
X d @ d2=10%
22.3 mm Displacement limit due to IM distortion (Doppler)
Parameters at the Rest Position
The value of the nonlinear parameters at the rest position (x=0) may be used as input for the traditional linear modelling and
may be referred as “linear parameters”. Please note that these parameters depend on the instantaneous state of the driver
(voice coil temperature, peak value of displacement) and are presented for three different modes of operation:
Mode Properties
LARGE+WARM the transducer is operated in the large signal domain, the peak value of the displacement is high (|x| < xmax), the variation of
the parameters is not negligible, the voice coil temperature is increased (D TV > 0) due to heating.
LARGE+COLD the transducer is operated in the large signal domain, the peak value of the displacement is high (|x| < xmax), the variation of
the parameters is not negligible, the effect of heating is compensated while considering the cold voice coil resistance Re(D
TV =0
).