It is easy to understand how loud a speaker will sound and comparing them just by looking at some specifications. You will need two values, RMS and sensitivity.
Power Handling of Speakers
RMS is the speaker's continuous power handling level. You can adjust your speaker's maximum power input to its RMS level and you can use it for a long period.
There is another power handling value called "Peak Power". This the power handling level of speakers before failing. If you match your speaker's maximum power input level with peak power handling level, sooner or later you will obtain a blown off speaker.
Sensitivity of Speakers
The sensitivity of speakers is a measurement done by power speaker @ 1 watt and measuring the sound intensity by 1 meter away. It is a direct comparison for different speakers and their sound-producing capacity at the same power input levels.
Some producers choose to give @2.83V/1m values for the sensitivity values. If you want to transform that value to @1watt/1m value it should be, you just look at their impedance level.
- Impedance 8 ohm = no change,
- Impedance 4 ohm = -3 dB
- Impedance 8 ohm = -6 dB
For example, you come across a speaker that has 4-ohm impedance and 89 dB sensitivity @2.83V/1m. Then you can easily calculate that this speaker has 86 dB sensitivity @1watt/1m.
You Know RMS and Sensitivity? Good, that is Enough!
It is time for another small calculation. If you have enough power supply level in your head unit or amplifier, what you need to do is comparing speakers at the RMS power input level.
Doubling power input will increase the sound intensity by +3 dB. So,
- 2 watts = Sensitivity +3 dB
- 4 watts = Sensitivity + 6 dB
- 8 watts = Sensitivity + 9 dB
- 16 watts = Sensitivity + 12 dB
and so on. You can calculate this according to different RMS and Sensitivity levels of different speakers and easily compare them in terms of their loudness levels.