First of a disclaimer - I'm a hobbyist and quite the beginner at that, so bear with me.
What I'm trying to build is a metronome with an astable 555 oscillator that is driving an 8 Ohm loudspeaker. I have gathered some experience with 555's now and have already completed this project with a piezo.
In that case I used two 555 oscillators, one that produces the square wave and one that uses a transistor to turn the first one on and off at the desired beats per minute.
Now I've looked into how to do it with a loudspeaker and have found these guides:
Safe to say I'm quite confused, baffled even. They all just use one astable 555 that represents the bpm. Don't loudspeakers need an AC signal? My piezo does.
How do they turn on the loudspeaker with just the "on period" of the duty cycle?
I suspect it has something to do with the capacitor in series with the loudspeaker but it would be nice if someone took the time and explained it to me.
PS: My confusion in a simple picture:
EDIT: As requested, I added a schematic of the mentioned piezo circuit below.