What a frequency-response graph shows (and what it doesn't)

A frequency-response (FR) graph plots how loud a headphone or IEM plays each frequency from deep bass (20 Hz) to the upper treble (20 kHz), measured on a standardized test rig. Tonal balance (is it bassy, bright, shouty, veiled?) is the single biggest factor in how a transducer sounds, and FR captures it well. If two headphones have genuinely matched frequency response on the same rig, they will sound remarkably similar in tonality.

What FR does not directly show: soundstage width, imaging precision, 'speed', 'detail retrieval', or dynamics. Some of these correlate partially with FR features (treble energy often reads as 'detail'; a 3 kHz dip can read as 'distant staging'), and some depend on things a single FR sweep does not capture: fit, seal, distortion at high playback levels, and how the earpiece interacts with your specific ear geometry.

The practical reading order: first check the bass level relative to the midrange (warmth vs leanness), then the 1-4 kHz region (presence and vocal energy: too much is shouty, too little is veiled), then the 5-10 kHz region (sibilance and sharpness). Small wiggles under about 3 dB, especially in the treble, are usually rig artifacts or unit variation rather than audible signatures.

Also remember that a published curve describes one unit, on one rig, with one insertion or placement. Your unit, your ears, and your tips or pads all shift the in-situ response. Treat graphs as a strong prior, not a verdict.

On qfiAudio, FR graphs always name the measurement rig and the measurer, and curves from different rigs are never overlaid on one chart.