How do you match speaker ohms to match a 4 ohm ampandHow many speakers can you add?

The amplifier will have an output impedance of around 0.04 ohms. We don't use matching. In hi-fi we have always impedance bridging. Zout << Zin.

The damping factor DF = Zin / Zout tells you what Zout is.

Zout = Zin/DF.

If the damping factor DF = 200 and the loudspeaker impedance is Zin = 8 ohms, the output impedance of the amplifier is Zout = 8 / 200 = 0.04 ohms.

You see, there is no "8 ohm amplifier" with a 8 ohm output.

Scroll down to related links and look at "Amplifier, Loudspeaker, and Ohms".