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Technical Data - Loudspeaker Sensitivity (SPL)
SPL represents one of the most useful specifications published for any loudspeaker. It is a representation of the efficiency and volume you can expect from a device relative to the input power. This is important because it requires twice the power to increase the volume of a speaker by 3dB. For instance, to increase the volume of a 50W guitar amplifier by 3dB (an audible, but relatively small amount), it would require 100W of power. The same outcome could be achieved more economically by replacing the speaker with a model that is 3dB more sensitive.
Loudspeaker manufacturers follow different rules when obtaining this information. Always ensure that you compare like for like when looking at the sensitivities of different manufacturers loudspeakers. Most manufacturers determine sensitivity by measuring the sound pressure level at one metre, with 1W of input power. The preferred method is to measure with the microphone one metre from the baffle board. Then take the frequency response curve and points across the specified usable frequency range to obtain the average sound pressure level (SPL). This method is extremely accurate and represents exactly what you can expect from the transducer in a specific application.
Although sensitivity is important, be sure not to buy your speakers based on efficiency alone. You must be willing to compromise to get your ideal combination of low-frequency reproduction and sensitivity. If you have lots of power, you can have awesome low frequency reproduction and maintain lots of volume from a speaker with lower sensitivity. On the other hand, if power is a consideration, you may want to sacrifice some low frequency reproduction in order to maintain a higher sound pressure level.
As a comparison, think of a car. If all you do with your vehicle is drive a few miles to work each day, you can probably get by with a small, efficient compact car that has less than 100 horsepower. On the other hand, maybe you car share and carry six other people to work with you. In that case, you need a larger, more powerful car. The end result is you give up efficiency but are doing much more work. The key with loudspeaker selection is to choose the loudspeaker that offers you what you need in terms of low-frequency reproduction, but has the best sensitivity in it's class.
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