SPL level of Headphones.com frequency response measurements

1

I have a question about the SPL level at which Headphones.com performs its frequency response measurements.
In their measurement and methodology pages (B&K 5128, compensation, targets), I can’t find any explicit mention of a fixed SPL level, such as 85 dB or 90 dB SPL.
The reason I care is that, because of the equal loudness curves, a frequency response that looks “flat” at a higher test level is not necessarily perceived as flat at more typical listening levels around 60–70 dB SPL.
Does anyone know whether Headphones.com uses a fixed SPL reference for its FR measurements (and if so, which), or do they simply use a fixed voltage and then normalise/compensate the graphs?

1 Like
2

For passive headphones, there’s no specific SPL value required unless testing for harmonic distortion. For active headphones that do have dynamic volume dependend equalization, like Airpods for example, we have to test by the increments available. But as far as depicting it, that’s typically around 85dB for raw data (this equalization depends on crest factor of the music, so 85dB is fine).

If you’re wondering if the response itself changes based on SPL, with passive headphones the answer only in extremely rare cases. But I think this is more a question about the preference bounds, which is pulled from the actual results in the Harman research.

Is there a specific headphone measurement you’re concerned about?

2 Likes
3

Thanks for the clear explanation above.

I usually tune my headphones to a neutral DF slope (about --0.8 to --1 dB/oct), but I tend to listen around 60 dB SPL. At that level, EQ adjustments based on measurements and sweeps feel less reliable, likely because of the equal‑loudness curves: the physical FR stays the same, but the perceived neutrality shifts. That’s why I’m trying to understand which reference level makes the most sense when deriving loudness‑related corrections. Many measurement practices seem to assume something around ~85 dB SPL.

Is ~85 dB SPL a sensible baseline for calculating loudness corrections down to lower listening levels (like 60 dB), or is there a better reference point to use? (I own a Sennheiser HD 550)

4

I feel 85dB is a fine indication of ‘typical listening’, and would be appropriate for anyone listening slightly lower as well.