To your original question. Rms is (are) the mechanical loss(es) of a driver. Mostly suspension related, such as viscous drag in the material. Some rubber surrounds have very high loss, foam usually low. Electrodynamic loss is here also, so aluminum voice coil formers will have lower Q. Forcing air through a cloth suspension is also an Rms contributor.
Rms is the resistance that determines Qms. (High mechanical drag gives low mechanical Q.)
David