Audio

Frequency response, headphone jack
20 Hz to 20 kHz, +0.05/-1.25 dB

Frequency response, speakers
230 Hz to 10 kHz, ±3.5 dB

Signal-to-noise ratio (0 dBFS, A-weighted)
-84.5 dB

THD+N (0 dBFS, 1 kHz)
0.039%

Output impedance
approx. 2 ohms

I measured the frequency response at the HTC One's headphone jack using a test tone made up of a series of sine waves in 1/3rd-octave steps from 20 Hz to 20 kHz, with the headphone output feeding an Audio Precision System One Dual Domain audio analyzer. First I measured with the Beats audio mode switched off, normalizing the measurement to 0 dB at 1 kHz. Then without changing any other settings on the phone or the Audio Precision, I made the same measurement with Beats audio switched on.

With Beats off, the HTC One's output measures reasonably flat, at +0.05/-1.25 dB. The -1.25 dB number is at 20 kHz; the results at 20 kHz varied a bit with every sweep, and this is the best result I got. Bass roll-off is -0.5 dB at 20 Hz. When I switched Beats on, output fell by -2.1 dB at 1 kHz, and a narrow +3.5 dB peak (relative to the level at 1 kHz) appeared at 70 Hz. The top octave of treble, above 10 kHz, was also boosted, by a maximum of +2.5 dB at 20 kHz. While that treble boost may or may not be noticeable, depending on your hearing acuity and the headphones you use, that big bass bump at 70 Hz will definitely be audible.

I measured the frequency response of the HTC One's internal speaker using an Audiomatica Clio FW audio analyzer in FFT/RTA mode, and the MIC-01 measurement microphone designed for use with Clio. I measured using a pink noise test tone. I positioned the microphone within about 10mm of the speaker, and ran the measurment first with Beats deactivated, then with Beats activated but without changing any other settings on the phone or the Clio.4

With Beats off, the response shows a strong bias toward the midrange, especially the region between 600 Hz and 1.4 kHz. With Beats on, the response is much, much flatter: roughly ±3.5 dB from 230 Hz to 10 kHz. There's also much more upper bass response, between 150 and 230 Hz.

I measured other characteristics using my NTI Minilyzer handheld audio analyzer with a 0 dBFS 1 kHz test tone. All were better than I expected from a mobile device.

-Brent Butterworth