Weighted Harmonic Distortion Scores and Tests

Headphones

Hello! There’s a common perception that a “normal” listening level shouldn’t exceed 100dB SPL. However, I think a headphone should handle bass levels with peaks around 120dB (or even higher at very loud volumes, such as 95dBA RMS). Consider the Audeze LCD GX, which has a sensitivity of 100 dB/1mW. Despite this, its minimum power requirement is over 100mW, and the recommended power level is over 250mW. This means that at 250mW, these headphones can reach about 124dB. Evaluating distortion at this level might be quite challenging, but I think it’s worth it. Perhaps using new stimulus signals, like sine bursts, could help measure this accurately. Understanding distortion at higher volumes is crucial for assessing headphone quality post-equalization, particularly in the lower frequencies. This measurement might also explain why planar headphones, like the Audeze LCD GX, sound distinct from dynamic ones—most dynamic headphones struggle to reproduce bass levels up to 120dB.

Hi Heedong_Kang, thanks for your question. I’ll start with the second question.

Harmonics are captured up to the 10th harmonics. Each of them gets weighted proportionally to their order (more weight in high order harmonics) and then filtered in the lower bass band since distortion is abnormally high in the lower spectrum in most headphones which make the value unrepresentative, and inaudible in real life. Up until this step, it would look like these weighting curves

We then filter with an inverse equal loudness curve to represent the actual perception. The results are average to give us the final value.

hello Thank you for always providing good information I have a question about weighted thd item

1. What is the weghting curve?
2. How many harmonics do you measure?