Bose QC25 Headphones Review
The new QC25s from Bose aren't perfect, but they're a worthy successor to the QC15s.
The Insides That Count
The Bose QuietComfort 25 over-ears (MSRP $299.95) deliver a consumer-friendly sound, great isolation, and low amounts of distortion—as long as active canceling is on. Without it, the sound stage suffers dramatically, and sub-bass/bass elements gain notably more harmonic distortion. The solution? About $4.79 for a four-pack of AAA copper tops.
If there's one place the QC 25 over-ears shine without question, it's in the isolation department. Our isolation test measures a set of headphones' ability to isolate noise both with and without an active noise canceling feature triggered, measuring their natural isolation ability as well as the improvements made by triggering the active noise canceling.
With ANC on, the QC 25 over-ears reduce sub-bass/bass tones around 20 dB, meaning they're reduced by 25% of their original volume. While midtones aren't affected as prominently (only around 15-20 dB), high-mid and high-end frequencies are dampened by 25-35 dB, sounding out at only one-eighth of their original volume.
Like most ANC-equipped cans, these Bose offer up a different soundscape depending upon whether or not their canceling feature is active. We measure the frequency response with ANC turned on and off, and found major differences in bass and midtone emphasis, as well as fairly notable differences between the left and right speaker channels.
With ANC enabled, the QC 25 over-ears give plenty of emphasis to sub-bass and bass tones, mustering a flat, even response that's sure to please audiophiles. This emphasis tapers very gently from ~80 dB to ~75 dB at the 1kHz midrange point, dropping off notably for high-mid trebles and spiking again (slightly) around 6kHz. The result is a consumer-facing sound that's nevertheless subtle and well-balanced—save for a period of under-emphasis right around 3kHz.
With ANC turned off, the soundscape is thrown off-balance. It's the sub-bass range between 20 and 60 Hz that takes the biggest hit, dropping from a healthy 80 dB playback to ~75 in the left channel and closer to 70 in the right channel. This volume discrepancy between channels doesn't stop there, actually: Across the entire frequency spectrum, the left/right channels are out of sync in terms of volume. There's also a notable lack of emphasis between 1.8kHz and 6kHz, which means a lot of details lost.
Total Harmonic Distortion
Distortion, the natural presence of mechanical sounds and/or clipped harmonics or bass tones during speaker playback, can be the bane of an otherwise stellar set of cans. Akin to their frequency response test, the Bose QC 25 over-ears perform much better with ANC turned on than when it's off, again compelling consumers to simply never run out of juice.
With ANC enabled, distortion is kept very low: Even the sub-bass range, the most distorted frequency range, never rises above ~10% THD. This number quickly drops to below 3% distortion—the ideal amount—between 60 and 10kHz.
With ANC turned off, things change quite a bit. THD within the sub-bass range (audibly, ~20 Hz–60Hz) jump between 25% and 40% THD depending on the channel analyzed, which is much higher than anything reported while ANC was on. The right channel, in particular, peaks just above 3% THD into the bass range above 60Hz, which is a notably worse result compared to when ANC is on.
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