The likelihood that you get any kind of meaningful arc from puncturing a speaker is almost none, theyre not gonna drive those speakers with high voltage. Especially improbable since you’re likely just destroying the speaker diaphragm, so an arc may not even be feasible from the type of damage done.

When myth busters tested whether cell phones, and then arcing (like from static discharge) would blow you up at the gas station, they had to use a large continuous arc from a neon sign transformer (extremely high voltage) and a sealed box full of the ideal fuel to air ratio of gasoline vapors to get an explosion.

Puncturing a speaker isnt unlikely to ever have to have either of those things. You’re unlikely to get an arc, and there should be like a zero percent chance of a meaningful build up of fuel vapors in an open air setting where the vapors have to make out of the narrow choke of the fuel tank opening, where the nozzle and its rubber splash guard thing are blocking its route, and all the way to where the speaker is

Do you by any chance have any experience working with electricity to back up your concerns?