Microphone types: condenser, ribbon, electret, polar patterns and phantom power.

A microphone specification sheet looks like a list of unrelated numbers, but each figure answers a specific question: what energy it converts, how much noise it adds, what level it can withstand and which directions it listens to. Choosing by price or brand often leaves you with a microphone that overloads on the chorus, picks up the PA return or introduces background noise that is impossible to remove from the mix.

This guide covers the three capsule types you will find in catalogues—Condenser, Ribbon and Electret—polar patterns and the two most misunderstood specifications, Max SPL and Self-noise. It ends with phantom power, the supply carried along the same signal cable that causes more than a few pops on the line.

Capsule types: condenser, ribbon and electret

Condenser describes a capsule made from a very thin diaphragm placed in front of a fixed plate: together they form a capacitor whose capacitance changes with air movement, producing an electrical signal. Because the diaphragm weighs very little, it responds quickly to transients and achieves a flat, extended frequency response. In return, its internal electronics—the capsule preamplifier—need power and contribute their own noise, as well as a maximum signal level beyond which they distort.

Within this family is the Electret: a condenser capsule whose polarising charge is permanently embedded in the plate or diaphragm material, without an external high-voltage generator. This design dominates lavaliers, headsets and screen microphones because it allows very small sizes; it still contains active electronics, however, so it still needs power: bias from a wireless transmitter or phantom when connected by XLR.

The Ribbon is a passive variation of the dynamic principle: a strip of corrugated aluminium a few micrometres thick suspended between two magnets. It needs neither power nor electronics, offers a smooth high-frequency response and a very low output, requiring clean preamplifier gain. Its fragility is physical: a strong gust of air, blowing on it or an impact can deform the ribbon, which is why manufacturers’ manuals advise against phantom power unless the model explicitly states that it is compatible.

By contrast, a conventional dynamic has no electronics or significant self-noise: it withstands stage use, handling and high SPL, but performs less well for distant pickup and detail. The practical rule is not “better” or “worse”, but where the source is, how much level surrounds it and whether you can provide gain without raising the noise floor.

Polar patterns and their effect on stage

Polar patterns describe the directions in which the capsule is sensitive. An omnidirectional picks up equally from all angles, has no proximity effect and sounds most natural for lapel and room use; a cardioid rejects sound arriving from behind, making it the default booth pattern; supercardioid and hypercardioid narrow the front pickup cone but leave a sensitive rear lobe, so a monitor directly behind them enters through the back. Figure-of-eight listens to the front and rear and rejects the sides, which is very useful for MS technique or separating instruments.

Three practical consequences:

• Feedback: the rejection angle matters as much as system gain. A cardioid pointed incorrectly towards the PA performs worse than a well-positioned omni.
• Background noise and spill: greater directionality means less ambience, but also greater dependence on distance and axis.
• Movement: for a moving voice—presenter, MC or performer—an omni maintains a constant timbre, whereas a cardioid penalises every turn of the head.

The wireless systems guide also explains how the polar pattern interacts with attenuation of the antenna by the body.

Max SPL and self-noise: the two limits of a specification

Max SPL is the sound pressure level at which the microphone’s electronics begin to distort, typically at 0.5 % or 1 % THD. It does not measure the capsule “breaking”; it measures how far it can deliver clean audio. This is why studio condensers publish values of 130 to 150 dB and include a 10 or 20 dB attenuation pad: if the source is a brass chorus or the PA itself, you engage the pad and regain headroom. A microphone without a pad that sounds distorted close to a snare drum is not faulty; it is at the limit of its specification.

Self-noise, the equivalent noise level in dB-A, measures the noise the microphone itself generates in silence. It sets the limit on what you can capture: an ambience recording or a falsetto voice with a lot of gain approaches the noise floor before the source. The signal-to-noise ratio is simply the difference between the reference level, 94 dB SPL, and self-noise: 79 dB S/N versus 64 dB S/N is an audible difference in quiet recordings.

How to use them together: for a drum kit or amplifier, put Max SPL first; for a soft voice, distant strings or a quiet room, look at Self-noise. Sheets such as the Neumann TLM 193’s publish both—140 dB Max SPL and 10 dB-A self-noise—precisely so they can be compared in the same units.

Phantom power: what it is, when to use it and when not to

Phantom power is a 48 V DC voltage—the P48 standard; manufacturers accept ranges from 11 to 52 V—that the mixer or preamplifier sends down the microphone cable itself: it appears equally on pins 2 and 3 relative to the ground on pin 1. Because the difference between the two pins is zero, a balanced dynamic microphone sees no current flowing through its output and is not damaged. Phantom can therefore remain enabled on dynamic inputs, with no precaution beyond avoiding pops when connecting.

Cases that do require care:

• Classic ribbons and models not stated to be compatible: turn phantom off before plugging or unplugging, check the manual and, if in doubt, use a preamplifier without phantom on that line.
• Electrets and lavaliers: many receive 1.5 to 9 V bias through a single conductor, which differs from phantom. A microphone expecting bias from a transmitter will not work correctly with only 48 V from a mixer, and vice versa.
• Adapters and chains: any XLR-to-jack adapter that breaks the balanced connection stops distributing the voltage symmetrically; check the wiring before blaming the microphone.

Golden rule: switch phantom on or off with the system open and the fader down, and never with your hand on the capsule.

How to read a specification sheet without getting lost

Before buying, work through the sheet in this order and relate it to your use:

1. Capsule type and polar pattern: where is the source sounding, and what is behind it?
2. Required power: phantom, bias, battery or none. This determines whether it fits your mixer, interface or transmitter.
3. Self-noise and sensitivity: the microphone’s own noise and how much gain you will need for the target level.
4. Max SPL and pad: for close-miking or high levels, check the headroom.
5. Output impedance and connector: low-impedance outputs, 150-600 ohm, allow long cable runs; high-impedance ones lose treble over a few metres.
6. Frequency response and filters: a built-in low-cut prevents rumble on voice, but also cuts body from a choir.

If the sheet does not publish self-noise or Max SPL, that suggests the manufacturer is emphasising something else: these are precisely the figures that separate a studio microphone from a stage microphone.

Choosing by application

Live voice with an open monitor → cardioid or supercardioid dynamic. Choir, strings or room pickup → large-diaphragm condenser with a pad. Lapel presenter or event host → omnidirectional electret in a lavalier or headset. Strings and overheads with a quality preamplifier → ribbon. For studio voice recording, the usual combination is a condenser with an available pad and a preamplifier providing clean gain, as explained in the vocal recording guide.

None of these decisions can be changed in the mix: capsule, pattern and power are chosen before sound starts, and define the ceiling for everything else.

Next step

Once capsule types and specifications are clear, the next hurdle is practical: how to position, power and back up these microphones at a real event. Continue to lavalier microphones, headsets and failover for weddings and interviews.