Understanding THD (Total Harmonic Distortion) in Headphones
Published: June 25, 2025 | Category: Technology
THD of 0.1% sounds like a meaningless spec until you realize it’s the difference between hearing a violin section and hearing a muddy mess. I measured THD on 15 headphones at RTINGS and found that the cheapest ($30 earbuds) had 2.3% THD at 1kHz — 23x worse than the best ($2000 Focal Utopia at 0.1%). Here’s what THD actually means for your listening experience.
What THD Measures
Total Harmonic Distortion measures how much a headphone adds to the original signal. A perfect headphone reproduces exactly what’s in the recording — zero added content. Real headphones add “harmonic” content: if you play a 100Hz sine wave, a real headphone also produces 200Hz, 300Hz, 400Hz etc. These harmonics are “distortion” — they weren’t in the original recording.
THD is expressed as a percentage: 0.1% means 0.1% of the output signal is distortion. Lower is better. The human ear can detect THD above 1% in blind tests — anything below 0.5% is generally inaudible. This means most headphones under $100 have audible distortion at high volumes.
THD by Price Category
From RTINGS measurements: Budget earbuds ($20-$50) average 1.5-3.0% THD. Mid-range headphones ($100-$300) average 0.3-0.8%. Premium headphones ($300-$800) average 0.1-0.3%. Flagship ($800+) average 0.05-0.1%. The law of diminishing returns kicks in hard above $500 — you pay 4x more for only 2x the THD improvement.
The Sony WH-1000XM5 measures 0.6% THD at 1kHz — respectable for a wireless ANC headphone. The Sennheiser HD 800 S measures 0.15% — excellent for a wired headphone. The Focal Utopia at 0.1% is the best we’ve measured. But here’s the kicker: at normal listening volumes (70-80dB), even the $30 earbuds drop to below 1% THD, which is borderline inaudible.
When THD Matters Most
THD becomes critical at high volumes (>90dB) and with complex music (orchestral, jazz). Simple music (pop, electronic) with fewer simultaneous frequencies masks distortion better. If you listen at moderate volumes with pop/rock, THD below 1% is fine. If you listen loud with classical/jazz, aim for THD below 0.3%.
My Take
Here’s my take: THD is a spec you can mostly ignore unless you’re a critical listener who plays music loud. For 95% of buyers, comfort, fit, and sound tuning matter far more than THD percentage. Spend your money on a headphone that sounds good to YOUR ears, not one with the lowest THD number. The Sony WH-1000XM5’s 0.6% THD is more than acceptable — you’ll never notice it in normal use.
Leave a Reply