here is an article by Richard Clark (from Autosound Magazine)
Richard Clark11-14-2002, 12:07 PM
guys--------stuffing the box with polyfill has the effect of converting SOME OF THE PRESSURE CHANGES INTO HEAT-----adiabatic means the the system would be loseless regarding applied energy and really does not relate to pressure specifically-------with any spring (except a textbook perfect one that does not exist in nature) there is at least some isothermal effect------the air in the box is a reactance (spring) and when energy is applied (the spring is squeezed)------ the spring returns the stored energy when released------since there are no perfect springs all the energy is not returned-----the energy is lost as heat when the material in the spring flexes------this is no different with an air spring in a woofer box or a car suspension spring------the polyfill makes the box a more lossy system by absorbing SOME OF THE ENERGY by converting it to heat-----that leaves less spring pressure to push on the speaker cone------but the system by no means becomes totally isothermal (meaning all the energy would be converted to heat)-------if it were the box would behave like it was an infinitely large resistance and would resemble a transmission line-----------bottom line?????-------like i have posted about a jillion times-------the effect is subtle at best and does not make a very large (if any) audible difference..........RC
[ November 14, 2002, 12:09 PM: Message edited by: Richard Clark ]