The Heiserman H251 is a premium large-diaphragm valve microphone designed for professional studio recording, offering versatile polar patterns and meticulous vintage-inspired engineering.

Overview

Engineered with precision for demanding studio environments, the Heiserman H251 features the Generation 4 Hk12 capsule, constructed with brass and an acrylic-chambered backplate. The capsule utilises 6-micron gold-sputtered DuPont Mylar® to achieve superior transient response and sonic clarity. Two master machinists in North Carolina handcraft every component, ensuring exceptional consistency and mechanical precision.

Internal Design

The microphone incorporates a faithful recreation of the original 251 circuit, including an acrylic circuit board, full acrylic head assembly and the original rotational pattern switch for selecting cardioid, omnidirectional or figure-8 polar patterns. The head assembly houses the authentic Ck12 saddle with felt and foam damping for mechanical stability.

Electronic Components

The circuit employs high-spec Vishay and Takman Rex resistors, alongside NOS polystyrene and PIO capacitors, delivering consistent tonal performance. The output stage features a true-to-original wet Tantalum capacitor, enhancing harmonic detail and warmth.

Transformer and Tube

The T14/1 transformer, reverse-engineered from a pristine 1961 vintage unit, delivers balanced output with enhanced low-end response and smooth high frequencies. The microphone runs a 6072 TAD Premium Highgrade vacuum tube, providing low noise performance and classic valve character.

Construction and Finish

The Heiserman H251 features a robust metal body with an automotive-grade Siemens Grey painted finish for durability and aesthetic authenticity. The system ships with a custom bulletproof power supply with global voltage switching, a 7.5-metre Sommer tube microphone cable with a custom 251-style connector, and a rugged flight case for secure transport.

Performance

The microphone offers a sensitivity of 17mV/Pa ±1dB, a frequency response spanning 20 Hz to 20 kHz, and a maximum SPL handling of 130 dB. The self-noise measures just 10dBA, ensuring pristine recordings, while selectable impedance options of 200 ohms or 50 ohms provide flexibility for different recording chains.