Impedance
All speaker have a certain amount of impedance which is a frequency-sensitive function. They have typic impedance values in the rang shown in Fig1. Nominal impedance is a speaker impedance at a particular frequency, usually the one above the lowest resonant frequwncy (fo) at which the speaker has the lowest impedance.

Frequency
A practical frequency response for a speaker is the frequency range within which the speaker output will not drop by more than 10dB from the rated output sound pressure level.

Input Power
The input to a speaker is defined as follows: P=E2/Z
P: input power (W)
E: voltage across the voice coil (V)
Z: nominal impedance (Ω)

Maximum allowable input power
Themaximum input(rms) power containing various frequency spectrums, applied
repeatedly for 1 minute every 2 minutes, on which the speaker can operate regardless of distortion without being damaged.

Output sound pressure level
Output sound pressure level is defined with an input of the rated power at 4 different frequencies applied to the speaker terminals. The output is defined as SPL which is dB relative to 2×10-5Pa at the average value.