As Timber_MG said.
I will still be 'pushing the envelope' by the following, hopefully not pulling attention away from Decibel's original purpose for this thread. Here follow the T-S characteristics of an Infinity Dynamic 20cm loudspeaker, model R8520, as determined 'on the bench' by me. (I have used several of these):
BL = 6,32 t.m fs = 36,7Hz Mmd = 22,1gm Mmr = 1,5gm Mms = 23,6gm Cms = 8,06 x 10(power -4) m/N Qes = 0,88 Qms = 3,3 Qts = 0,69 Levc = 1,1mH Revc = 6,9ohm Vas = 42 l (1,5 sq. ft)
It will be apparent that Qts is rather high for many uses, also there is bound to be a tolerance as Timber said. I did not test several examples for control.
Also to state that I am not an agent for Infinity Dynamic and have no connection with them. (In fact, I was rather disappointed by the scant attention received at my last visit to their Jo-burg agents.) But the above for comparison.