How to test second hand speakers - advice please

I'm going to buy some second hand mid/tops cabs. Obviously I need to hear them running to make sure they sound fine. Can anyone give me any advice as to what checks to make to ensure they are fully funtioning, as this is my first purchase. I'm told you can use computer software to check their frequency response, but is this workable? Also is it worthwhile/standard practice to open the cab to check what drivers are inside?

I don't have the ears or experience of a sound engineer so will not be able to test speakers adequately by ear unless it is absolutely knackered. Any advice greatfully recieved.

A sine sweep is nice if you're setup for it(have it burned on a disk, lappy, or MP3 player) and the current owner has something to power the speakers with and accept your input device, but you also have to have some awareness of the speakers in question so you don't damage them with this and so you know what to expect from a good set. Mid/top cabs as the name suggests won't produce much lowend so there's no point getting hung up on that, concentrate instead on midrange clarity and high end detail. It also helps to bring a music track that you are intimately familiar with and something that should expose the strengths and weaknesses of the boxes under audition, in this case something with strong vocals for example and maybe a loud cymbol crash.

Also compare one speaker with the other if they are sold as a pair. They are supposed to sound strictly the same, except if one has been damaged...if available, play with the balance knob to quickly switch between left and right

As well as a multimeter, a 9volt battery can quickly check if all of the 'speakers are wired properly in phase by looking at the cone movement
Mik