ampeg svt 18 cab problem!

[herman]

is there any way possible to find out what rms rating the 18" speaker is? could it be done with speaker still in cab?
i know its 8ohms but there is no wattage rating on speaker anywhere, any idea how to solve this? on the back of cab
it says 500w rms and 4ohms, but i know for fact the driver is 8ohms.

[Mr. Foxen]

RMS rating doesn't tell you anything useful anyway, so not much point in knowing it. If you are wondering what sort of power head to use, the answer is any, they all have a volume control somewhere along the kine. Listen for the cab farting out, if it does, back off the volume, if that isn't loud enough, you need more cabs.