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Loud-speakers

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There's nothing mechanically or electrically complex about a speaker. It's a coil and a magnet attached to a bit of paper/plastic.

High-order crossover filter?

Well, if we're going there, we might as well just delve into the whole Active Speaker thing and get into the amplifiers.

But a basic speaker (driver) that's been around for decades is essentially a small linear motor: one moving part and very simple in operation.

2-way and 3-way speakers have been around for longer than I've been alive.

"Loud speaker" surprises me. Are you sure they don't use semiconductors for amplification?

Speakers? Definitely not. The amplifier will, but not the loudspeakers. That's basically a magnet, a coil, and a paper cone.

And, as someone mentioned above, usually a RLC filter

Cheap loudspeaker products, like [1] often have built-in amplifiers.