Neumann TLM 50
A 12mm diaphragm suspended in a 40mm sphere. The geometry does the polar-pattern work, and the transformerless electronics keep it quiet.
Overview
The TLM 50 is Georg Neumann GmbH's modern dedicated omnidirectional pressure microphone. The TLM prefix puts it in the transformerless solid-state family, and the "50" ties it to the classic M50 concept. It is a condenser mic built around a pressure transducer. It is not a multi-pattern capsule switched to omni. It is a single-diaphragm pressure design. The spec sheet doesn't show how much that matters. An omni setting on a multipattern mic is typically two back-to-back cardioids summed, and it inherits their off-axis behavior. A true pressure transducer generates its omni output from one diaphragm, so the polar response holds together differently across the band.
The headline numbers are respectable rather than spectacular. Neumann rates the frequency range at 20 Hz to 20 kHz, sensitivity at 28 mV/Pa into 1 kohm, and the equivalent noise level at 7 dB-A (18 dB CCIR). Self-noise that low lets an omni work on quiet sources and distant pickup without hiss getting in the way. Maximum SPL for 0.5% THD is 134 dB, rising to 144 dB with preattenuation engaged. That is enough headroom for close work on loud sources if the pad is in. Signal-to-noise is 87 dB-A (76 dB CCIR), maximum output voltage is 10 dBu, and the mic draws 3 mA from standard 48 V phantom power.
It is a substantial piece: approximately 850 g, 60 mm in diameter and 152 mm long, with an XLR 3 F connector. The rated impedance is 50 ohms and Neumann asks for a load of at least 1000 ohms. This is no lightweight handheld. It is a stand-mounted studio tool, and the weight comes from the housing and the spherical capsule assembly.
Key Features
12mm Pressure Capsule in a 40mm Sphere
The defining feature is the capsule geometry. A small pressure capsule sits in the surface of a sphere about 40mm in diameter. Period coverage describes the diaphragm as a single nickel membrane roughly 12mm across. The sphere shapes diffraction around the assembly and controls the pressure build-up in front of the diaphragm. That is how a pressure transducer ends up with extended high-frequency behavior while staying linear down low. Neumann's own description, repeated in contemporary announcements, gives pressure-transducer operation at low frequencies and a response that behaves more like a pressure-gradient design up top. Studio Sound (March 1991, p.22) reported the launch and noted the 12mm capsule mounted within the 40mm sphere as the mic's central design idea.
Transformerless Solid-State Electronics
TLM means transformerless circuitry. The TLM 50 belongs with the modern solid-state Neumanns, not the valve-era designs whose numbers it echoes. That means no output transformer in the signal path, phantom-powered operation at 48 V, and a low current draw of 3 mA. The payoff is the noise floor and headroom figures above: 7 dB-A self-noise and a 10 dBu maximum output.
Omnidirectional Pattern with Deliberate HF Directivity
This is a dedicated omni. There is no pattern switching. But because of the sphere-and-capsule arrangement, directivity increases gradually in the upper range while the low end stays a linear pressure response. That is why the TLM 50 turns up in spaced-pair and ambient work. It picks up a coherent low end without proximity effect, and the top end tightens enough to keep the picture from smearing. Period coverage repeatedly describes the design as exploiting the sphere's pressure build-up and diffraction rather than summing cardioids.
Pad and Low-Frequency Filtering
Two switches handle the practicalities. A pad reduces the capsule's polarization rather than attenuating downstream, which is the cleaner approach. It buys the extra 10 dB of headroom (134 dB to 144 dB) at the capsule. A high-pass filter tames the bottom. The low-frequency performance is strong enough that a permanent 30 Hz rolloff is built in to protect following equipment, and the switchable filter cuts below 100 Hz.
XLR Output and Phantom Powering
The output is a standard XLR 3 F, and the mic runs on 48 V phantom at 3 mA. The 50-ohm rated impedance into a 1000-ohm minimum load is an easy load for any competent preamp.
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