Estimate dB SPL loudness of headphones given a signal level.
How to Use
Look up the sensitivity/efficiency of your headphones, and set the units accordingly. Enter the impedance of the headphones. Then enter the desired signal level and click Calculate.
This calculator assumes a 0Ω output impedance amplifier. If your amplifier has a high output impedance, the loudness will be reduced by an additional attenuation value, which can be found using the output impedance calculator.
Sample 1: Finding a headphone’s loudness
Say you want to find out the maximum loudness of a Sennheiser HD650 (nominally 300Ω) when driven by a Focusrite Scarlett 2i2. From measurements online you find that the 2i2 manages to output 8 mW into 300Ω before clipping. Sennheiser advertises that the HD650 produces 103dB SPL at 1Vrms input.
Plugging 103dB/V, 300Ω, and 8 mW into the calculator, you find that the HD650 will max out at 106.8 dB SPL when driven by the 2i2. Since the average level of music is usually around 15dB lower than the peak level, you determine that the highest undistorted music loudness with the HD650 from the 2i2 will be roughly 90dB.
Sample 2: Finding a headphone’s sensitivity
Note: you can also perform this same calculation more directly using the sensitivity calculator.
Say you have measurements of a headphone’s loudness or a headphone specified using nonstandard units and you want to find its sensitivity. For instance, the Campfire Honeydew is specified as 17.44Ω, “94 dB SPL @ 1kHz: 17.68 mVrms”.
Plug in 0.01768 V (converted from mV) as the input level, and 17.44Ω as the impedance. Now using these values, find a sensitivity value that produces 94dB as the output. Blindly guessing using 100dB/mW as the sensitivity produces 82.53dB output. To get 94dB output would require an additional 11.5dB, so enter 111.5dB/mW as the sensitivity (since 100dB/mW+11.5dB/mW = 111.5dB/mW). The calculator now outputs 94.03dB, which roughly matches Campfire’s specification. So the Campfire Honeydew’s sensitivity is roughly 111dB/mW when expressed in standard units.
As another example, the Logitech G433 is specified as 32Ω, “107 dB@1KHz SPL 30 mW/1cm”. Plug in 30mW as the input power, and 32Ω as the impedance. Again blindly guessing using 100dB/mW as the starting point for sensitivity returns 114.77dB output. This is 7.77dB higher than Logitech’s 107dB value, so the sensitivity must be 7.77dB/mW lower than the 100dB/mW starting point. Entering 92.23dB/mW as the sensitivity now produces 107dB output. So the Logitech G433’s sensitivity is roughly 92dB/mW when expressed in standard units.