Reading a Datasheet: What the Numbers Really Say

The sensitivity needs a reference: 1 W / 1 m or 2.83 V / 1 m. At 4 Ω, the 2.83 V value is 3 dB above the 1 W value. Some datasheets even give two different values – for the 18 Sound 15W700, alongside 99 dB without a reference, there is a reference efficiency of 97.8 dB.

The test method is part of the power handling. The datasheet of the Fane Colossus Prime 18XS describes it precisely: pink noise, bandpass 30–300 Hz, driver suspended in free air, two hours. Program and peak power are derived from this and are not continuous values.

Xmax is sometimes calculated geometrically, sometimes measured via a distortion limit. How a manufacturer proceeds is not always stated. Our driver pages recalculate the geometric Xmax from winding height and gap depth if both values are given, and show deviations as “different definition” – not as an error.

For the PD.185N02, the datasheet states “Xmax 12 mm / 22 mm”; the stated displacement volume matches 12 mm.

The frequency response in the datasheet shows the driver in a measurement enclosure, not in the later plan. For the Fane it says: measured in half space in a sealed 975-litre enclosure. You cannot read the low-frequency extension for a different enclosure from such curves.

Besides the nominal impedance, the minimum is important: for the Fane it is 6.5 Ω for an 8 Ω driver. With several enclosures connected in parallel, the minimum decides whether the amplifier still operates within the permissible range.

Typos and contradictory data do occur. In that case we do not silently adopt a value, but show both with their location in the source – see methodology.