Adding to what others have already said:

Speakers will have poor bass response if they are not in a proper enclosure which (a) holds the speaker solidly still so that it doesn't just flap back and forth in the air, and, (b) cleanly separates the airmass in front of the speaker from the airmass behind the speaker (i.e., a good seal). Then, the size of the airmass behind the speaker will determine the bass response, for instance, if they are in a small box, the bass response will still be poor.

Sometimes you will see speaker boxes with a tuned "port" which controls the amount of bleed between the air masses. This redirects the backpressure waves into the narrow frequency range of that tuned port, allowing you to get away with a smaller enclosure at the expense of making the bass response only be good at that one frequency.

I seem to recall that we discussed this in the past here on the BBS. Here's also some links:
https://www.crutchfield.com/S-p2F4lEaHkIG/learn/car-subwoofer-boxes.html
http://education.lenardaudio.com/en/05_speakers_4.html