Measuring loudspeakers

Measurement turns speaker design from trial and error into a repeatable process.

Basic equipment

A useful measurement setup includes:

A frequency-response measurement compares microphone level with frequency.

Record and document:

A time window can exclude later room reflections, approximating free-field behavior at mid and high frequencies.

The trade-off is low-frequency resolution: a short time window cannot resolve deep bass accurately.

Placing the microphone close to a woofer or port reduces the room’s influence and improves low-frequency signal-to-noise ratio.

Nearfield results usually need scaling and careful splicing to far-field measurements.

Placing the source and microphone close to the ground reduces one major reflection and can be useful outdoors or in a sufficiently large space.

Measure at several horizontal and vertical angles. This reveals directivity and crossover behavior that an on-axis curve cannot show.

An impedance sweep helps identify:

A speaker can behave differently as level increases. Repeat selected measurements at increasing drive levels while remaining within safe limits.

Look for:

Begin at low voltage.
Never exceed driver excursion or thermal limits.
Protect tweeters from accidental low-frequency signals.
Do not connect a computer interface directly to a power-amplifier output without an appropriate attenuator.
High sound levels can damage hearing.