A lot of the time people seem to measure how loud a sound system is by how many watts it is. This can be misleading. After all, are they talking about watts RMS? Watts Program? Or what the amp is actually delivering to the speakers? In the real world how loud a sound system is, is defined by the SPL (Sound Pressure Level) and should be measured in dB.
To really understand how loud a sound system is you need to be a bit more scientific than just looking at the power. It is a combination of the sensitivity of the loudspeaker, how much power it is receiving and how many cabinets there are. Here is an example of how it works. To get us started we have compared a Zeus 4 with a normal reflex bassbin. Zeus 4 | | | | Reflex Cab | | | | | | |
| | | | | | = | Sensitvity at 1w/1m | = | | | | | | |
2.4Kw
| = | Program Power | = |
1.2Kw | | | | | | |
= | SPL at Program Power | = | | | | | | | | = | SPL at 1.2Kw |
= | |
If you put a pair of loudspeakers together and double the power it will be 3dB louder. Double it all again and you will only get another 3dB and so on. This means that you need more speakers with more powerful amps to get the same SPL from reflex cabinets as you would from a Zeus 4 soundsystem. Not only do you need to buy more gear it also means higher storage costs, higher transport costs and a bigger crew. Lets look at those numbers again. This time we will show how a 2.4kw Zeus sound system is as loud as a traditional 7.2kw sound system. 2x Zeus 4
| = | Just as Loud | = | 6x Reflex Cab | | | | | | | | | | | | = | Sensitvity at 1w/1m | = | | |
| | | | | | = | Total power of system | = |
7.2Kw | | | | | | | = | Total SPL for system | = |
| | | | | | | = | Logistics | = | |
Maths For those of you who want to know the maths here are the equations. For SPL from the loudspeakers sensitivity and power- SPL =10*LOG10(power/1)+sensitivity For the difference in SPL when you add more cabinets- SPL = 20LOG(a*10^(b/20)) a= how many cabinets
b=SPL per cabinet | 
