Review and Measurements: Bose QC25 Noise-Cancelling Headphone

01
of 09

A New Version of an Industry Standard

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Brent Butterworth

The Bose QC15 has long been the standard for noise canceling headphones because its noise canceling is so much better than anybody else's and it sounds pretty nice. Suddenly, Bose is replacing it with the QC25, a headphone that costs the same ($299) and offers one especially nice new feature: the QC25 still works in passive mode when its batteries run down, which the QC15 didn't.

Bose claims the QC25 sounds better, is more comfortable and is made from more high-quality materials with a better finish. The QC25 also 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 somewhat clunky bayonet-style mount on the QC15. For an additional $100 (gulp), it comes in your choice of toothpaste-inspired colors.

Distracted by the IFA show in Berlin, I hadn't even heard about the QC25 until my colleague Geoff Morrison told me he'd bought a pair and reviewed them for Forbes.com. He asked if I'd like to give them a listen and run some measurements, and of course, I eagerly agreed.

02
of 09

Bose QC25: Features and Ergonomics

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Brent Butterworth

• 4.5 ft/1.4 m detachable cord with iOS-compatible mic/remote
• Active noise canceling with on/off switch
• Takes one AAA battery
• Can be used in passive mode when batteries run down
• Carrying case included
• Weight: 6.9 oz/196 g

As you can tell from the photo above, the QC25 at left closely resembles the QC15 at right. Not that I'm complaining, because discarding a design that works so well would be ... well, pretty much what most mainstream electronics companies do every year.

Again, the key feature here is that the QC25 still works when the battery runs down. Also, its case (shown on the next page) is smaller, more rectangular and easier to slip into a computer bag.

To me, the feel and comfort of the two headphones were about the same. And that's good because I don't know of a headphone that's more comfortable than either of these. I once wore the QC15 through an entire flight from Seoul to L.A. and never experienced the slightest bit of discomfort. It's actually a little frustrating because comfort is the area where other manufacturers could equal Bose, but they don't bother to try. (Matching Bose's noise canceling is tougher because the company owns several patents on the process and has  notoriously diligent lawyers.)

03
of 09

Bose QC25: Performance

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Brent Butterworth

My experience with the QC25 came between trips to two shows -- IFA and CEDIA -- and was thus rather brief. My colleague Geoff Morrison, who loaned me the review sample, got in a much longer listen, which you can read about in his Forbes.com column. Geoff also brought over a sample of the QC15 for comparisons.

Usually, the first of my all-time-favorite test tracks that I use with headphones is Toto's "Rosanna," because it's so sonically dense and takes up almost the entire audio spectrum. It was obvious to me that the QC25 and QC15 are a lot more alike than they are different. The big difference, to my ears, was in the bass. The QC25 seemed to have a stronger resonant peak in the low bass, maybe around 40 Hz and below, which gave kick drum and the lower notes of the bass guitar more dynamics and punch. This made the QC25 sound just a little bit more like something Beats would make. (It's also noteworthy that Bose is now cultivating celebrity endorsements, including Seattle Seahawks QB Russell Wilson.) Score: QC25 1, QC15 0

Another must-play for me when doing quick evals is James Taylor's live version of "Shower the People" from Live at the Beacon Theatre. Here, I noticed that the QC25's mild bass boost seems to affect the lower midrange slightly, which made Taylor's voice seem a little heavier than it should. I also noticed an apparent boost in output in the lower treble, somewhere around 2 or 3 kHz, which gave Taylor's voice a slight "cupped hands" coloration, as if he had his hands lightly cupped around his mouth when he was singing. (This might seem bad but it's an extremely common coloration in headphones, and it seems to be more common in closed-back designs.) Score: QC25 1, QC15 1

Hearing the QC25's heavier bass, I next opted for Mötley Crüe's "Kickstart My Heart." Here, the QC25's punchier, more present bass worked perfectly, giving the tune an extra kick that made the QC25 a lot more fun to listen to than the QC15. To me, the QC25's tonal balance is just about perfect for music like this. Score: QC25 2, QC15 1

Bose headphones have never had a rep for sounding super-detailed or especially good with more delicate recordings, so I figured saxophonist David Binney's purely acoustical recording "The Blue Whale" (from Lifted Land) would be a great test. While neither headphone distorted during the intense upright bass solo at the beginning, the QC25's more powerful and resonant bass made the sound seem a little boomy compared with the QC15. Also, with the QC25, that same coloration I heard before in the lower treble seemed to give the saxophone a less open and natural sound. Score: QC25 2, QC15 2

I listened to a lot of other material, but don't need to detail it here because the results were about the same. With some tunes I preferred the QC25, with others I preferred the QC15. The two headphones sound different, but a clear favorite never emerged in my listening.

When I switched the QC25 to passive mode (noise canceling off), I wasn't thrilled with the sound. It seemed lifeless and somewhat bloated, without much detail or depth. But at least it'll still sound a lot better than the headphones the airlines provide.

I got a similar result when I tested the two headphones' noise canceling. Both did a great job of canceling the pink noise produced by my testing rig when I was running my measurements. When I set up the Butterworth Airplane Sound Simulator (B.A.S.S.), with two Genelec speakers and a Sunfire sub reproducing a recording of cabin noise I made in a 737, the results were again about the same. The QC25 and QC15 both did a great job of eliminating the droning of the jet engines, and a reasonable job of reducing the noise of the ventilation system and the other passengers' conversations.

04
of 09

Bose QC25 Measurements: Frequency Response

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Brent Butterworth

The chart above 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 NC on; it's a fairly "by the book" headphone response that shouldn't have any severe colorations. Obviously, though, the sound will be a lot different with NC off; there's less deep bass, more mid and upper bass, and -5 to -10 dB less treble response.

I measured the performance of the QC25 using a G.R.A.S. 43AG ear/cheek simulator, a Clio FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-Can headphone amplifier. Measurements were calibrated for ear reference point (ERP), roughly the point in space where your palm intersects with the axis of your ear canal when you press your hand against your ear. I experimented with the position of the earpads by moving them around slightly on the ear/cheek simulator and settled on the positions that gave the most characteristic result overall.

05
of 09

Bose QC25 Measurements: Active NC Mode, Passive Mode and Vs. QC15

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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; for the NC off measurement, I did not adjust the level. 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 dB more treble energy above 2 kHz. Again, it's clear that the QC25 in passive (NC off) mode sounds a lot different from either headphone inactive (NC on) mode.

06
of 09

Bose QC25 Measurements: Isolation

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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). (The QC15 was a recent sample and its results vary a little from the sample I measured a few years ago, which I have shown previously on this site; maybe that's because the headphone changed a little, or maybe it's due to gradual and subtle improvements in my measurement technique.) Levels below 75 dB indicate attenuation of outside noise -- i.e., 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 of these headphones deliver excellent noise cancellation, which in my experience can be beaten only by Bose's own QC20 in-ear NC headphone. However, the QC25 doesn't seem, at least in this measurement, to improve substantially on the QC15's performance. It actually appears to be slightly outperformed by the QC15 between 200 and 600 Hz.

07
of 09

Bose QC25 Measurements: Spectral Decay

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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 (something I usually see in closed-back headphones), but a very strong resonance around 1.35 kHz.

08
of 09

Bose QC25 Measurements: Distortion and More

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Brent Butterworth

This graph shows the total harmonic distortion of the QC25 measured at 90 and 100 dBA (set with pink noise generated by the Clio). These are very high listening levels, and the 100 dBA test I do mainly because some headphones pass it and some don't, not because you'd actually listen that loud. The distortion is a little higher than I'm used to measuring, although mainly at very 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). Would you hear this? Probably not; the threshold for audible distortion in subwoofer testing is often considered to be around 10 percent.

Unfortunately, I forgot to measure impedance, but with an active (i.e., noise canceling) headphone, this is seldom a concern because the internal amp provides all the power. I did note, though, that unusually for an active headphone, the frequency response changed slightly when I switched to 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 was 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; normally I see a bass boost when I switch in the extra source impedance.

Because I couldn't find a published impedance spec, I measured sensitivity at 32 ohms, which is what I use for most active headphones. Sensitivity 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 inactive (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.

09
of 09

Bose QC25: Final Take

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Brent Butterworth

The QC25 is better than its predecessor in three ways: It looks cooler, its case is smaller and it still produces sound even when the battery runs down. From a performance standpoint, it seems like just a slight reshuffling of the QC15's characteristics -- kind of like when Microsoft introduces a new version of Word by moving things around on the interface rather than adding significant new features.

But that's perfectly OK. The QC15 earned a spot at the top of numerous "best noise canceling headphones" lists, and the QC25 will surely do the same. These are very good and very popular products, so if it ain't broke, why fix it?