An Electret Microphone is a type of condenser microphone that eliminates the need for a high-voltage polarizing source. It achieves this by using a specialized dielectric material called an "electret," which is permanently permanently charged with a static electric field during the manufacturing process.

Because the capsule is permanently polarized, these microphones do not need 48V phantom power to charge the capacitor plates. However, they almost always still require a small DC voltage (often from a battery or lower bias voltage) to power the internal impedance converter (usually a JFET) that buffers the capsule's incredibly high impedance output. The term "Back Electret" referenced in the original text denotes a specific, superior construction where the charged material is applied to the stationary backplate rather than the moving diaphragm, resulting in a lighter diaphragm with better transient response and stability over time.