Induction Dynamics® SolidDrive® is a powerful hidden sound transducer that transmits acoustical energy through almost any solid surface. The entire surface becomes a speaker delivering high-quality sound and the frequency response of conventional diaphragm speakers. SolidDrive® provides a distinct advance for audio systems used in home theater systems, distributed audio, and other high-performance audio applications. SolidDrive® works with rigid surfaces that include glass, drywall, granite, metal, wood, ceramics, laminates and composites. Because the SolidDrive® utilizes materials already existing in a room, it’s ideal for installed home audio, commercial audio, or a home theater sound system anywhere an invisible sound source is needed.
They also have passive EQ for different materials