What Is MAX SPL & How Is It Calculated
Speakers will sometimes come with a MAX SPL rating. SPL stands for Sound Pressure Level and is measured in dB (Decibels).
MAX SPL is how loud (in dB) a speaker’s output sound is at a listening distance of 1 meter. This is calculated using two metrics, a speaker’s sensitivity rating and it’s maximum power rating (Watts).
A speaker’s sensitivity rating is how much sound (in dB) a speaker outputs, using only 1 watt of power from a listening distance of 1 meter. So if I provided a speaker 1 watt of power, stood 1 meter away and measured the volume in decibels, the result would be that speaker’s sensitivity rating. A typical professional speaker will have a sensitivity rating of anywhere between 85 – 100 decibels.
In order to get a speaker’s MAX SPL rating we need to increase the power from 1 watt to the MAX power rating for that specific speaker. Starting at the speaker’s sensitivity rating, we need to double the power input to increase the output sound by 3 decibels.
For example: If I have a speaker with a sensitivity rating of 85 dB to increase the sound output to 88 dB I will need to double the power. So this speaker will need 2 watts to produce 88 decibels, 4 watts to produce 91 decibels, 8 watts to produce 94 decibels etc. You can start to see why it takes a lot of power to make a speaker play very loud.
Unfortunately many manufacturers do not accurately measure a speaker’s sensitivity rating which results in the MAX SPL being purely theoretical. Manufacturers will use the known sensitivity of the speaker’s transducer and the known MAX power rating of the amplifier to work out the MAX SPL. The resulting SPL figure does not include sound loss through a speaker’s enclosure and other factors such as protective limiting and differences in how speakers handle high, middle and low frequencies. Mackie (a top brand in the digital sound industry) conducted a case study to find out if the stated manufacturer’s MAX SPL ratings were accurate compared to their actual listening SPL level. They found consistently lower results measuring a speaker’s SPL in the real world against what the manufacturer had stated. Click here to read more on this case study.
Is MAX SPL an accurate way to compare speakers?
If a speaker’s MAX SPL is worked out using estimated MAX power and sensitivity rating, then no this isn’t very accurate. If the MAX SPL is worked out by actually measuring the volume from 1 meter, using an accurate sensitivity figure, then yes. However, most manufacturers will use theoretical figures to work out the MAX SPL, so you should take this number with a pinch of salt.