active vs passive speakers

so do you need to own four amplifiers...two per side?

so do you need to own four amplifiers...two per side?

For two way main speakers you will indeed need four power amplifiers for an active configuration. You also need a preamp section that will split the line level audio signal between the two power amps for each speaker. In an active speaker this is usually all built into the speaker for covenience - so you just connect your XLR plugs from your source/preamp to the speaker.

What you will not often find inside an active speaker is tubes. Since tubes are microphonic it is generally a bad idea to put them inside a speaker - tube amplification would require the amplifiers installed in an area away from large amounts of vibration (although this could still be an active design in principle)

The other interesting thing to point out here is that it can be much simpler to adjust active speakers for different rooms with their non-uniform environments across the frequency spectrum.

With simple trim pots you can adjust the level of each frequency band independantly without affecting the cross-over function or having to resort to an external equalizer.

Small (< .5dB) changes can be quite significant.