The SM137 is a versatile, flat-response cardioid condenser probe microphone. The SM137 has an ultra-thin diaphragm for a frequency response that combines a smooth high-end with a tight, controlled low-end and a 15db pad for natural sound reproduction in both acoustic and high volume performance applications. Features Ultra-thin diaphragm for smooth high end and tight, controlled low end15dB pad for performance consistency across a wider range of high SPL sourcesLow self-noise and transformerless preamplifier circuitry Specifications: Type Permanently Biased CondenserFrequency Response 20 to 20,000 HzPolar Pattern Cardioid Warranty: 2 years.