Older tube amps with output transformers need a load on each (if they're stereo), so you'd need a plug with a resistor across it for the second channel. Solid state amps are not liable to such damage, and can have any number of speakers attached. I have one with two output jacks, but you can use just one, even daisy-chaining the speakers if you have two and room for 'em. So the amp can be between the speakers (using both jacks) or at one end of the speaker chain.

Bob