Dayton Audio PS220-8 8" Point Source Full-Range Neo Driver - Manual (Page 8)

Kms Symmetry xc(x)
This curve shows the symmetry point in the nonlinear compliance curve where a negative and
positive displacement x=xpeak will produce the same compliance value
kms(xc(x) + x) = kms(xc(x) – x).
A high value of the symmetry point xc(x) at small displacement amplitudes x » 0 indicates that the
rest position does not agree with the minimum of the stiffness characteristic. This may be caused by
an asymmetry in the geometry of the spider (cup form) or surround (half wave). A high value of the
symmetry point xc(x) at maximal displacement x» xmax may be caused by asymmetric limiting of
the surround.
You can find a detailed description of these non-linearities and their remedies in the papers
“ Loudspeaker Nonlinearities - Causes and Symptoms , Assessing Large Signal Performance of
Loudspeakers , and “Diagnosis and Remedy of Nonlinearities
Testing performed by Redrock Acoustics – www.redrockacoustics.com