How does the size of a speaker affect its frequency response
Reducing the size of the speaker enclosure will cause the dB of some frequencies to be higher compared to the rest of the frequencies.
The speaker consists of an enclosure, a driver and a crossover. The speaker enclosure is normally made from hard wood like plywood or MDF (Medium Density Fiber). The enclosure will help to hold the speaker driver in place and also absorb the vibrations from the driver.
The diaphragm of the driver moves back and forth to create sound. The forward movement of the diaphragm will cause the air pressure inside the enclosure to drop and the backward movement of the diaphragm will cause the pressure inside the enclosure to rise.