Ok, so my synth plugs into my amplifier, with my talkbox going through the amplifiers output, as shown in this picture

However in the diagram on the back of the talkbox and in several others it shows another cable from the other side of the talkbox into a 'speaker enclosure'.
Why is this? I thought a Talkbox worked with the sound from the amplifier going into the tube (and only coming out of the tube), why do you need both an amplifier and a speaker system?
So, basically. How the hell do i set this thing up?
