Frequency Characteristics:

The frequency characteristics of a loudspeaker refer to the pattern of the loudspeaker's output sound pressure on its reference axis varying with the frequency of the input signal, while the input signal voltage remains constant. It is a frequency response curve (abbreviated as "freq. response") that varies with frequency, reflecting the loudspeaker's radiating capability for different frequency sound waves.

The frequency range for standard bass speakers is between 20Hz and 3kHz, for mid-range speakers it's between 500Hz and 5kHz, and for treble speakers it's between 2kHz and 20kHz.

Directionality:

The sound pressure frequency characteristics of a speaker vary with the direction of radiation, a property known as the speaker's directivity. It is related to the speaker's diameter; a larger diameter results in a sharper directivity, while a smaller diameter yields a wider directivity. Directivity is also frequency-dependent. Generally, for manufacturers of speakers, there is no significant directivity for low-frequency signals below 250Hz. However, there is a clear directivity for high-frequency signals below 1.5kHz.

Sensitivity (dB/W):

The sensitivity of a loudspeaker typically refers to the sound pressure level measured at 1 meter in the axis direction on the front of the speaker, when a noise voltage of 1W is applied. Sensitivity is a measure of a loudspeaker's ability to reproduce the details of an audio signal accurately. The higher the sensitivity, the more responsive the speaker is to all the details within the audio signal. Manufacturers advise that the sensitivity of a Hi-Fi loudspeaker should be greater than 86dB/W.

Distortion:

There are various types of distortion in speakers, with common ones in speaker manufacturing including harmonic distortion (often caused by an uneven magnetic field in the speaker and distortion in the vibration system, typically occurring at low frequencies), intermodulation distortion (resulting from the degradation of sound quality when two different frequencies are simultaneously input into the speaker, causing mutual modulation), and transient distortion (due to the inertia of the vibration system not being able to keep up with the signal changes, leading to signal distortion). Harmonic distortion refers to the addition of harmonic components not originally present in the playback signal. The harmonic distortion in speakers originates from non-linear distortions such as an uneven magnetic field in the magnets, the characteristics of the vibration membrane, and the displacement of the voice coil. Currently, the better speaker harmonic distortion indicators do not exceed 5[%].