Characteristic sound pressure
The characteristic sound pressure (often also referred to as sensitivity) in a loudspeaker is the sound pressure level that is generated when a constant voltage is applied at a defined distance, measured in dB SPL per watt and meter .
It is the sound pressure level dB SPL that a loudspeaker achieves under test conditions (often between 125 Hz and 8 kHz {250 Hz and 4 kHz}) and with voltage adjustment at typically +9 dBV (2.83 V corresponding to 1 W electrical signal power at 8 ohms) generated at a distance of typically one meter.
For example, the sound pressure level of a good loudspeaker is:
- 92 dB SPL (at 2.83 volts input voltage, at a distance of 1 meter).
It is important to specify other test conditions (test signal, bandwidth).
Here is the electrical reference power
This is not about the degree of efficiency , as it is often incorrectly mentioned in the data sheets, but rather the characteristic sound pressure .
No manufacturer dares to state the very low efficiency of loudspeakers. The usual values are between 0.2% and a maximum of 3% for hi-fi speakers and studio monitors , i.e. between 0.002 and 0.03. The sound power is not important in daily practice and can only be estimated or measured with great effort (spatial integration or reverberation room ).
For loudspeakers with an integrated amplifier (here the amplifier and converter form an electrically specially coordinated unit in a common housing), e.g. B. with the so-called active loudspeakers and many control loudspeakers, the characteristic sound pressure can only be given for a certain input voltage to be named or its level.
Incorrect information on the efficiency of loudspeaker data
In the loudspeaker data, the efficiency is rarely given in percent, but the characteristic sound pressure level in dB / W / m. Some loudspeaker manufacturers incorrectly call their measured data in dB / W / m "efficiency" and thus cause confusion, because the characteristic sound pressure cannot be the same as the efficiency.
The efficiency has to be converted into the characteristic sound pressure level in dB:
- Characteristic sound pressure level in dB = 112 + 10 log (efficiency).
| Characteristic sound pressure level | Efficiency | in percent |
|---|---|---|
| 102 dB | 0.1 | 10% |
| 99 dB | 0.05 | 5% |
| 95 dB | 0.02 | 2% |
| 92 dB | 0.01 | 1 % |
| 89 dB | 0.005 | 0.5% |
| 85 dB | 0.002 | 0.2% |
| 82 dB | 0.001 | 0.1% |
literature
- DIN 45570 Bl. 1, "Loudspeakers and terms, symbols, units"
- DIN 45573 Bl. 1, "Loudspeaker test methods, measurement conditions and measurement methods for type tests"