The previous posters are correct. Place the speakers face to face, as close as possible together without having them touch. Connect one of the speaker cables backwards (+ to -, - to +) which will cause one of the speakers to play out of phase with the other speaker.
The out-of-phase signals will cancel each other out to a great extent. If you have the ability to play a mono signal to both speakers, most of the output of the speaker will be cancelled since it's an identical signal going to both speakers. If it's not a mono signal, you will still get some output as the signal between the speakers is obviously not identical from a stereo recording. However since most of the "shared" signal in a stereo recording is low frequency, much of the low end will be cancelled and you will be able to play the speakers much louder without keeping everyone awake all night while you let the speakers break in! Adding thick blankets or sleeping bags as covers will also further reduce to sound from the speakers as they break in.
Lastly, be cautious. Before doing the out-of-phase trick, listen to the speakers and write down the position of the volume knob when you are playing loud. Do not inadvertently play the speakers "louder than loud" when out of phase. The reduced sound produced by the out of phase signal is still "loud" as far as the speaker is concerned and the drivers could be accidently pushed too hard without you knowing it.
Enjoy,
TIC