The walls of your house have major advantages over a normal loudspeaker enclosure which add enormously to sound quality - namely zero resistance, rigidity , and acoustic isolation.

ZERO RESISTANCE
Unlike all box loudspeakers,placing a loudspeaker in a cavity wall creates no back pressure on the cone and gives no resistance to the movement of the cone generated by the electrical signal - this means better bass, less phase changes, and no rear energy reflected back through the cone.

 RIGIDITY
The rigidity of a loudspeaker enclosure is a major factor in the ultimate quality of the loudspeaker. This is because every loudspeaker drive unit, as it vibrates, attempts to create vibration from the surrounding enclosure and baffle. If it succeeds then efficiency and transient performance is lost, but more importantly spurious resonance are created in the speaker enclosure panels which can be highly audible in their worst case.

Another major problem in loudspeaker enclosure design is the need to isolate the mid range and high frequency driver from the resonance caused by the bass unit. Both mid range and treble clarity suffers as a result of baffle or other resonance reaching the unit.

However, by using the walls of your house, we can use a structure far more massive than any box loudspeaker, with resonance virtually non-existent. .