How to Read a Headphone Spec Sheet Line by Line

Read impedance and sensitivity as a pair, treat frequency response ranges as marketing, and most specification sheets become useful. The sheet is a set of measurements with conditions attached, and the conditions are usually missing, which is where misinterpretation starts.

Frequency response range

A claim of 5 Hz to 40 kHz states the limits at which the headphone produces some output, at a tolerance that is rarely given.

Without a tolerance, the range is not comparable between models. A figure of 10 Hz to 30 kHz at minus 3 dB is a much stronger claim than 5 Hz to 40 kHz at minus 20 dB, and the two look similar on a page.

The shape of the response matters and never appears in the range. Two headphones with identical ranges can differ by 10 dB in the midrange.

Impedance

The nominal impedance is an average and is usually quoted at 1 kHz. The curve varies with frequency, often rising sharply at the driver’s low-frequency resonance.

Impedance alone does not indicate difficulty. A 32-ohm headphone with a deep impedance dip is a harder load than a 300-ohm headphone with a flat curve.

What it determines is the sensitivity of the response to the amplifier’s output impedance. Lower nominal impedance means greater sensitivity to that mismatch.

Sensitivity

Sensitivity is quoted in dB per milliwatt or dB per volt, and the two cannot be compared without conversion.

A dB/mW figure is a power rating and describes efficiency. A dB/V figure is a voltage rating and describes how loud the headphone will play from a given source, which is what you actually need to know.

Where only dB/mW is given, convert using the impedance: subtract 10 times the logarithm of the impedance divided by 1000, which for 32 ohms is about 10 dB.

Total harmonic distortion

A distortion figure is meaningless without the level at which it was measured. A rating of 0.1 percent at 90 dB says nothing about behaviour at 110 dB.

Where the level is stated, compare like with like. Most headphones reach 1 percent distortion at some level, and that level is the practical limit for clean reproduction.

Distortion at low frequencies is usually higher than at mid frequencies, which is normal for dynamic drivers and rarely audible in music.

Maximum input power

This figure indicates the level at which the driver may be damaged. It is usually generous and rarely reached in normal use.

It is more useful as an indication of the design’s headroom than as a limit to observe. A pair rated at 1 watt can typically be driven from any reasonable amplifier without concern.

The figure is quoted per channel and refers to continuous power. Short transients well above it are usually harmless.

Cable and connector specifications

Length, connector type and whether the cable detaches are the three items worth reading, because they affect daily use more than any electrical figure.

An unbalanced 3.5 mm connection is the standard. A 6.35 mm connector indicates a desktop design, and a 4-pin connector indicates a balanced option that may use any of several incompatible wiring standards.

Where the cable is fixed, the plug becomes the failure point. Detachable means a replacement rather than a repair.

Weight and dimensions

Weight is quoted in grams and predicts comfort less reliably than clamp force, which is rarely published.

The headband and cup dimensions tell you more in practice. A cup that is too small will press on the ear, and a band with limited travel will not fit a larger head.

Where the manufacturer publishes pad dimensions, read them. Pad depth and inner diameter affect both comfort and the measured response.

What the sheet cannot tell you

Comfort, clamp force, isolation, build quality and the shape of the frequency response are all absent or unreliable.

Use the sheet to eliminate candidates that cannot be driven by your source, then decide the remainder by listening and by trying them on.

Where to find better data

Independent measurement databases publish response curves on consistent rigs and are more informative than any manufacturer sheet.

Compare measurements taken on the same rig rather than across rigs. A curve from one database and a curve from another are not directly comparable in the upper midrange.

Where a manufacturer publishes measurement conditions, treat that as a good sign. Where none are given, treat the numbers as indicative rather than precise.