Reading Microphone Specs That Actually Matter
Microphone spec sheets are written to impress rather than inform. Frequency response gets a graph; the number that will actually decide whether you hear hiss is buried in a footnote.
The three that matter: self-noise (under 15 dB-A is quiet), sensitivity (low-output mics need strong preamps), and max SPL (only if your source is loud). Frequency response matters far less than the graph implies.
Self-Noise: The One To Check First
Every condenser microphone generates a small amount of noise from its own electronics, quoted in dB-A. Lower is better.
| Self-noise | Verdict | Suitable for |
|---|---|---|
| Under 10 dB-A | Exceptionally quiet | ASMR, foley, classical, nature |
| 10–15 dB-A | Quiet, professional | Studio vocals, voiceover |
| 15–20 dB-A | Acceptable | Podcasting, streaming, general use |
| Over 20 dB-A | Audible on quiet sources | Loud sources only |
When it matters: capturing anything quiet or delicate. Whispered vocals, ambient recording, solo acoustic instruments. If you amplify a quiet performance, you amplify the microphone's own hiss with it.
When it barely matters: close-miked speech and loud sources. A microphone 3 inches from your mouth receives a signal so much louder than 18 dB-A that the self-noise is irrelevant.
Dynamic microphones don't quote it: they have no active electronics to generate noise. With a dynamic, any hiss you hear comes from the preamp, not the mic.
Sensitivity: Why Some Mics Seem Quiet
Sensitivity describes how much electrical output a microphone produces for a given sound pressure, usually in mV/Pa. Higher means more output.
| Sensitivity | Type | Preamp requirement |
|---|---|---|
| 20–40 mV/Pa | Typical condenser | Modest, most interfaces fine |
| 8–20 mV/Pa | Low-output condenser | Reasonable gain needed |
| 1–3 mV/Pa | Typical dynamic | Plenty of clean gain |
| Under 1.5 mV/Pa | Low-output dynamic | Strong, quiet preamp essential |
This explains one of the most common frustrations in home recording. Certain well-regarded dynamic broadcast microphones have very low sensitivity. Plug one into a budget interface, turn the gain to maximum, and you hear both your voice and a layer of preamp hiss.
The microphone is not faulty and the interface is not broken. The microphone needs more clean gain than that preamp can supply. The usual answers are an inline preamp booster or an interface with stronger, quieter gain.
Buying lesson: check a dynamic microphone's sensitivity against your interface's available gain before purchasing. A low-output mic and a weak preamp is a genuinely bad pairing, and it is not obvious from either product page. More on levels in What Mic Gain Should I Use?.
Maximum SPL: Only For Loud Things
Max SPL is the sound pressure level at which the microphone begins distorting, in dB.
| Max SPL | Handles |
|---|---|
| Under 120 dB | Speech, quiet instruments |
| 120–135 dB | Most vocals and general recording |
| 135–150 dB | Drums, guitar cabinets, brass |
| Over 150 dB | Kick drums, very loud sources |
For reference: normal speech at close range is roughly 70–80 dB. A snare drum up close can exceed 140 dB.
If you only record speech, ignore this number. It will never be the limiting factor.
A pad switch (often -10 or -20 dB) attenuates the signal before the electronics, effectively raising the usable max SPL. If a microphone has one, it can handle louder sources than the base figure suggests.
Frequency Response: Less Useful Than It Looks
Frequency response is the range a microphone reproduces, quoted as something like 20 Hz – 20 kHz, usually with a graph.
The reason it deserves less weight than it gets: the range specification alone tells you almost nothing, because it rarely states tolerance. A microphone claiming 20 Hz – 20 kHz might vary wildly across that range.
What genuinely matters is the shape:
- Flat: reproduces the source with minimal colouration. What you want for capturing an instrument accurately.
- Presence boost: a lift around 3–8 kHz for clarity and intelligibility. Extremely common on vocal and broadcast microphones, and desirable there.
- Low-frequency roll-off: deliberately reduces rumble and proximity-effect bass build-up.
A tailored response is not a defect. It is voicing chosen for a purpose. A broadcast microphone with a presence lift and bass roll-off is better for speech than a perfectly flat one.
What The Spec Sheet Won't Tell You
Three things matter more than any number above, and none appear on a spec sheet.
Your room. A microphone with superb specs in an untreated room will produce a worse recording than a modest one in a treated space. This dominates everything else.
Your distance. Three inches versus eighteen inches changes your recording more than any spec difference between two microphones in the same price bracket. See How Far Should Your Microphone Be From Your Mouth?.
Whether the type suits your situation. A condenser with excellent self-noise is the wrong choice for a noisy bedroom, no matter how good the numbers are. See Condenser vs Dynamic Microphones.
A Practical Reading Order
When comparing two microphones, check in this sequence:
- Type: condenser or dynamic, given your room
- Polar pattern: does it suit how many people and what noise you have
- Sensitivity: can your preamp drive it cleanly
- Self-noise: only if recording quiet sources
- Max SPL: only if recording loud sources
- Frequency response shape: flat for accuracy, tailored for voice
- Connection: USB or XLR, per your setup
Stopping after step three is fine for most buyers. Steps four and five only bind at the extremes.
Rather than cross-referencing spec sheets by hand, the Microphone Selector Tool filters by pattern, connection, budget and recording environment together, and flags when a microphone needs phantom power or a strong preamp.
Related Guides & Tools
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