To get the best sound from your loudspeaker the use of cardboard tubes can enrich the sound and increase the bass quite dramatically.
As you can see in diagram 1 fitting one tube inside another allows you to experiment with the resonance length of the tube and in turn giving the sound that you like.
Once you achieve that sound use tape to hold the tubes at the given length and use hot glue or use contact glue to mount the speaker, making sure not to get glue on the working part of the speaker cone.
You could also make a 100mm cube out of cardboard or balsa wood, mount the speaker over a hole of the correct size for that speaker in the cube, and then add some holes to enhance the bass effect and allow the speaker to breath, see diagram 2.
I also suggest that you proved some ventilation in your model to allow the sound to get out of the model. Having a near airtight model will reduce the level of sound that you can hear.