The mechanical driver part of the subwoofer might be able to be made smaller, but the surface that moves the air still needs to be large - there is a relationship to the wavelength of the sound involved that I no longer remember. This is why tweeters are small.
Does this mean impossibly small subwoofers? Would the rotating part have to precisely match the audio frequency to be amplified?
The mechanical driver part of the subwoofer might be able to be made smaller, but the surface that moves the air still needs to be large - there is a relationship to the wavelength of the sound involved that I no longer remember. This is why tweeters are small.