The most likely thing to be blown with a newer cab is the hi-frequency horn. Arrange with the seller for the following:
Audible check of the cones:
While the amp is on, make a visual check that all the cones move when you play a note. A final check is performed by playing through the cab loudly, with your ear in close proximity to each cone (any distortion introduced by one of the cones will be hard to hear at a distance, but that situation leads to decreased speaker life).
Double check the cones:
Turn off and disconnect the amp. Lay the cab flat on its back and carefully remove the grill. Using both hands, gently move each cone back and forth, feeling carefully for any rubbing or scratchy sensations. Try to distribute the pressure evenly around the cone while doing this. Any rubbing or scraping indicates a deformed (blown) voice coil.
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