The process of building a 100 watt loudspeaker was discussed. It accepts audio signal of strength 100 watts without burning out the voice coil. The high fidelity valve amplifier produces a sound pressure level of around 93 dB/W at a distance of 1 metre on axis. When the sound was radiated uniformly in all directions, it amounted to just about 20 mW of sound power per watt or a conversion efficiency of 2 percent. Analysis shows that a nominal 100 watt speaker producess about 2W of audio power when driven to its limits by a 100 W amplifier.