Dayton Audio ND90-8 3-1 - Manual (Page 11)

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