The Brüel & Kjær 4191 is a 1/4-inch condenser measurement microphone designed for high-frequency and high sound pressure level applications. The smaller 1/4-inch capsule diameter extends the usable frequency range beyond what is achievable with a 1/2-inch capsule, and the reduced diaphragm area increases the maximum SPL before the mechanical linearity limit is reached. PLACID 1/4-inch Class 1 measurement microphones (PM400 series) are designed for the same application space.
ISO/IEC 17025 accredited calibration for 1/4-inch microphones is available from PLACID using the comparison method per IEC 61094-6 against a traceable reference. Calibration is performed at normal incidence across the full frequency range to 40 kHz. Contact PLACID for high-frequency calibration options and lead times.
If you are evaluating PLACID PM400 capsules as replacements for existing B&K 4191 capsules in B&K preamplifier housings, note that the 1/4-inch capsule thread and pin configuration follows the same IEC standard as the 1/2-inch range. PLACID confirms compatibility before processing any replacement capsule order. Sensitivity screening to a defined tolerance window and batch calibration are available for orders of five or more capsules, supporting a controlled transition in an existing measurement programme without full system recalibration.