Review and Measurements: Bose QC25 Headphone

This noise-canceling headphone is top of its class

The Bose QuietComfort 15 was long the standard for noise-canceling headphones because its noise canceling was so much better than anybody else's, and it sounded good. Bose replaced it with the Quiet Comfort 25 in 2014, a headphone that cost the same and offers a new feature: The QC25 works in passive mode when its batteries run down, which the QC15 didn't.

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New Version of an Industry Standard

Bose QC25
Brent Butterworth

Bose claims the QC25 sounds better, is more comfortable, and is made from higher-quality materials with a better finish than its predecessors. The QC25 comes with a case that's even more compact than the one provided with the QC15.  It has a new detachable cable that dispenses with the clunky bayonet-style mount on the QC15. 

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Bose QC25: Features and Ergonomics

QC25-QC15-side by side
Brent Butterworth

Bose QC25 features include:

  • 4.5 ft/1.4 m detachable cord with iOS-compatible mic/remote
  • Active noise canceling with on/off switch
  • One AAA battery needed
  • Passive mode when batteries run down
  • Carrying case included
  • Weight: 6.9 oz/196 g

As you can tell from the photo, the QC25 at left closely resembles the QC15 at right. 

The key feature here is that the QC25 still works when the battery runs down. Also, its case smaller, more rectangular and easier to slip into a computer bag.

The feel and comfort of the two headphones are about the same, and that's good because these headphones are both more comfortable than any of their competitors. As for the sound, it is hard to beat. Matching Bose's noise canceling is tough for competitors because the company owns several patents on the process.

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Bose QC25: Performance

QC25 with case
Brent Butterworth

The QC25 and QC15 are a lot more alike than they are different. The big difference is in the bass. The QC25 seems to have a stronger resonant peak in the low bass, maybe around 40 hertz and below, which gives kick drum and the lower notes of the bass guitar more dynamics and punch. This makes the QC25 sound just a little bit more like something Beats would make.

The QC25's mild bass boost seems to affect the lower midrange slightly, which can make voices seem a little heavy. There is an apparent boost in output in the lower treble, somewhere around 2 or 3 kHz.

Bose headphones have never had a rep for sounding super-detailed or especially good with delicate recordings. The QC25's more powerful and resonant bass made the sound seem a little boomy.

The QC25 passive mode with noise canceling off seemed lifeless and somewhat bloated, without much detail or depth, but it sounds a lot better than the headphones the airlines provide.

On a flight, the QC25 does a great job of eliminating the droning of jet engines and a reasonable job of reducing the noise of the ventilation system and the other passengers' conversations.

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Measurements: Frequency Response

Measurements: Frequency Response
Brent Butterworth

The chart shows the QC25's frequency response in the left and right channels, with noise canceling on and off. There's nothing particularly noteworthy in the response with noise canceling on. It's a fairly "by the book" headphone response that shouldn't have any severe colorations. Obviously, the sound is a lot different with noise canceling off; it has less deep bass, more midbass and upper bass, and -5 to -10 dB less treble response.

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Measurements: Active NC Mode and Passive Mode vs. QC15

Brent Butterworth

This chart compares the QC25's response with NC on and NC off to the response of the QC15 with NC on. (The QC15 doesn't work with NC off). The NC-on measurements are referenced to 94 dB at 500 Hz. Obviously, the QC25 shares many acoustical characteristics with the QC15. The new model has more low bass, a little less midrange energy around 1 kHz, and a couple of dB more treble energy above 2 kHz. It's clear that the QC25 in passive (NC-off) mode sounds a lot different from either headphone in active (NC-on) mode.

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Measurements: Isolation

Measurements: Isolation
Brent Butterworth

This chart shows the isolation of the QC25 right channel with NC off (green trace) and NC on (purple trace), compared with the QC15 (orange trace). Levels below 75 dB indicate attenuation of outside noise—for example, 65 dB on the chart means a -10 dB reduction in outside sounds at that sound frequency. The lower the line is on the chart, the better.

Both headphones deliver excellent noise cancellation. However, the QC25 doesn't seem, at least in this measurement, to improve substantially on the QC15's performance. It appears to be slightly outperformed by the QC15 between 200 and 600 Hz.

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Measurements: Spectral Decay

Brent Butterworth

This chart shows a spectral decay (or waterfall) plot of the QC25 with NC on. Long blue streaks indicate significant resonances. This shows a moderate amount of resonance in the bass, but a strong resonance around 1.35 kHz.

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Measurements: Distortion and More

Brent Butterworth

This graph shows the total harmonic distortion of the QC25 measured at 90 and 100 dBA. These are very high listening levels—you wouldn't listen at that volume. The distortion is a little high, although mainly at low frequencies. The 90 dBA curve is fairly typical with almost no distortion in the mids and treble and about 4 percent THD at 20 Hz. At 100 dBA, there's a distortion spike between 2 and 3 kHz, and a bit of bass distortion (3 percent at 60 Hz and below, rising to about 6 percent at 20 Hz). Could you hear this? Probably not. The threshold for audible distortion in subwoofer testing is often considered to be around 10 percent.

The frequency response changed slightly with a high-impedance (75 ohms) test signal source, which simulates what you'll hear when you use a low-quality headphone amp like the ones built into most laptops. The bass decreased by about -4 dB at 20 Hz, and the treble by about -1 dB above 4 kHz. Clearly, Bose is doing something a little differently here.

With the sensitivity at 32 ohms, it measured with a 1 mW signal between 300 Hz and 3 kHz at 32 ohms impedance, is 97.2 dB in passive (NC-off) mode and 101.3 dB in active (NC-on) mode. That's enough to give plenty of volume from any source with NC on, and enough from all but the weakest sources with NC off.

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Bose QC25: Final Take

Bose QC25 final
Brent Butterworth

The QC25 is better than its predecessor in three ways: It looks cooler, its case is smaller, and it produces sound even when the battery runs down. From a performance standpoint, it seems like just a slight reshuffling of the QC15's characteristics.

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