I have had good luck on this site for a long time by trusting my gut wrt dealing with people. The deal proposed by your buyer(s) is a known scam as pointed out by several here. The gold standard would be a local cash sale with local pick-up by the buyer. Anything less increases your risk and requires you to decide on the level of risk you are comfortable with in order to sell the speakers. Other options are to be patient and wait for a better buyer and/or to lower your price if you want to speed things up.
I agree with the suggestion to use PayPal and only ship to a verified address as recommended by @jasonbourne52 - but even with that option there are still risks that the buyer may claim shipping damage and lock up your account. Risks of real or imagined shipping damage claims increase when shipping large, expensive items such as speakers.
Unfortunately, bad actors act badly. This is a reason you sometimes see sellers require "a history of positive feedback" - a due diligence step that can reduce risks and protect a seller from one-time bad actors. Things you can do include requiring your buyer have prior positive feedback, requiring payment by PayPal (or that other payment methods clear prior to shipping), and only shipping to a verified PayPal address. Also, pack the speakers better than they were packed by the original manufacturer, and photo-document each step. Good luck.