You're at a gas station or passing through a parking lot when a guy calls to you from a van filled with stereo equipment. He says he works for a company that deals in high-end home theater systems for wealthy clients, and they just got done with an installation for which too many components were ordered. He shows you brand new speakers, amplifiers or digital projectors, still in their boxes, and says they're selling them at a loss because they can't be returned. He produces a brochure showing speakers priced at $849, the same ones he's willing to sell you for a mere $50.
How would you respond to this situation?
If you said, "walk away and don't buy anything," your instincts are correct.
The White Van Speaker Scam has been around for decades, at least since the 1980s and possibly earlier. It doesn't have to be a van, which doesn't have to be white, and they don't have to be selling speakers, but the basics remain the same: convincing a buyer that they are getting a big discount on high quality goods that turn out to be junk. It can happen in-person like the example above, or online through sites like Craigslist and Facebook Marketplace.
The items being sold always turn out to be garbage, no matter what jargon the seller throws at you. Speakers are almost never actually capable of handling the claimed wattage, cheap paper cones are concealed with fake ones, and the enclosures are often weighted with bricks or concrete to give them more heft (to make them "feel expensive"). Stereo components and projectors are similarly cheaply made, off-brand and occasionally non-functioning. There are cases where the box doesn't contain anything but rocks or bricks.
No professional home theater installer is ever going to "accidentally" order too many speakers or any other equipment. What company would have an order for a single 5.1 surround system and buy six more systems by mistake (and drive all six to the job site)? And even if they did, wouldn't they just warehouse the extras for the next orders? There's no rule that says, "we didn't use these supposedly-high-end electronic components today, therefore we either have to sell them at a loss or toss them in a dumpster."
However, you don't really need to think about it that much. You only have to remember two things: first, if a deal seems too good to be true, it is too good to be true. Second, don’t buy electronics from dudes in vans.