Does JBL have a defined set of parameters they base their Xmax specs on? According to this AES paper, there are a number of different ways this can be measured: AES comments on Xmax . I think I've noticed a couple of JBL spec sheets that mention Xmax at 10% distortion, but what type of distortion isn't mentioned.

Also, is Xmax a good indicator of maximum output at frequencies other than fs? For instance, if Xmax is .2" at 30hz fs, does it follow that an "equivalent" Xmax, (linear displacement at 10% distortion), at 60hz would be .1"?

John