Mazda Bose audio system in the RX-7 is implemented with the so-called Acoustic Wave Music System.
The subwoofer configuration is using two low frequency drivers, mounted face-to-face in an isobaric loaded configuration. This helps reduce the enclosure size by half of what it would be needed with only a single speaker. The speakers are placed on the left side of the car as you look at it from the rear.
