Sound amplification structure and building foundation structure

A speaker system comprising full-range speakers placed in a room of a building and capable of stereo sound reproduction without using a filter circuit, and a building foundation structure, wherein:

• the full-range speakers each including a single speaker unit,
• the building foundation structure comprises, sequentially from one lateral side to an opposite lateral side, a first underfloor subwoofer, a first sound amplification structure connected to a first of the full-range speakers, a second sound amplification structure connected to a second of the full-range speakers, and a second underfloor subwoofer,
• for each of the first sound amplification structure and the second sound amplification structure, a sound path having a first end and a second end is formed by an underfloor foundation of the building and a concrete peripheral wall formed by standing up approximately vertically from the underfloor foundation,
• the first end of the sound path is able to communicate with the single speaker unit to be placed in the room of the building,
• a width of the sound path widens from the first end to the second end of the sound path,
• the ratio of the width of the sound path at the second end to the width of the sound path at the first end is between 2 and 4,
• the second end of the sound path is able to output a sound that is emitted from the single speaker unit and amplified through the sound path,
• a length of the sound path is 4 m or longer,
• the first underfloor subwoofer and the second underfloor subwoofer are configured as bass-reflex types, wherein a subwoofer-side speaker unit is positioned within an area enclosed by the underfloor foundation and a second concrete surrounding wall that rises substantially vertically from the underfloor foundation, with both the front and rear sealed, and
• the first underfloor subwoofer and the second underfloor subwoofer are arranged relative to one another in a manner that is approximately symmetrically left and right in planar view.