... I have something to add about the Klippel test and the determination of Xmax.
The motor uses two coils and two gaps. When excusrion is low, both coils operate in the gaps for reduced distortion (gaps and coils are in opposing polarity). At high excursion, one cil drives the woofer forward and the other drives the woofer rearward. as soon as one coil leaves its gap, the BL falls, but the other coil is in its gap. This is one speaker for which the XMAX can't be accurately determined by measuriing BL.
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Product Marketing Manager
Harman Consumer Group
Mobile, Portable and Companion Products Division