Reviewed on: SoundStage! Solo, July 2021
I measured the Bowers & Wilkins P17 earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator with the RA0402 high-resolution ear simulator with KB5000/KB5001 simulated pinnae, and a Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. An Mpow BH259A Bluetooth transmitter was used to send signals from the Clio 12 QC to the earphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. Note that my usual impedance and sensitivity measurements are irrelevant for wireless earphones, and impossible to do without disassembling them, and are thus not included here. If you’d like to learn more about what our measurements mean, click here.
Note that the P17s were very fussy and intermittent when I tried to mate them with a Bluetooth transmitter (and I tried a few). Also, while you can turn the wear sensors off when the P17s are connected to their app, they default to on when the app is not used, and none of my usual methods for defeating the wear sensors worked. To do these measurements, I had to hold the ear/cheek simulator right next to my ear, then pull the P17 out of that ear and insert it into the simulator, then move the simulator around a bit until I got a test signal. So I wasn’t able to do as many measurements as I’d have liked, and some of my usual measurements are incomplete.
The above chart shows the P17s’ right-channel frequency response (because of the wear sensor, I couldn’t get the left to stay on long enough to measure it), measured with the RA0402 ear simulator. The shape of the curve isn’t terribly far from ordinary, with a big, broad bump in the bass and response peaks between 3 and 4kHz (fairly normal) and at about 11kHz (the likely cause of that subtle brightness I occasionally heard). However, the whole curve is tilted down, with substantially lower treble output relative to the bass output. Fortunately, the noise-canceling circuitry doesn’t seem to change the frequency response significantly.
This chart shows the P17s’ right-channel response compared with other true wireless earphones: the KEF Mu3s (which are the true wireless earphones I’ve found come closest to Harman curve), the Status Audio Between Pros, and the Grado GT220s. You can see that the P17s have the least treble—and thus, the softest sound—of the bunch.
The P17s’ spectral-decay (waterfall) response shows no significant resonances.
I was able to get only one distortion measurement of the P17s, at 90dBA. It’s a little higher than normal, but below 2% through almost all of the audio range, and considering how insensitive the ear is to transducer distortion, it’s unlikely you’ll notice any distortion at this fairly loud level.
In this chart, the baseline noise level is 85dB, and the various traces show how much of that noise reaches your eardrums—the lower the line is on the chart, the better the isolation. This chart shows the effects of the Ambient Pass-Through mode (which lets in most sounds) and also that at least in this test setting, there’s almost no difference between the normal NC setting and the Auto NC setting.
This chart shows the P17s’ isolation compared with several other true wireless earphones that include noise canceling. The P17s roughly equal the performance of the Sony WF-1000XM4s, which is pretty good considering Sony’s one of the leaders in noise canceling—but neither can match the Bose QC Earbuds.
Latency with the P17s connected to the Mpow BH259A Bluetooth transmitter typically measures about 236ms. That’s typical for Bluetooth SBC; although the BH259A is equipped with aptX Low Latency, the earphones don’t seem to have connected that way. However, latency dropped to 114ms when I used the charging case as the Bluetooth transmitter.
Maximum volume measured with pink noise from the P17s was 98.7dB when I used the charging case as the transmitter, connected to the headphone jack of my Samsung Galaxy S10 phone, and 108.6dB when I transmitted directly from the phone through Bluetooth. So my guess of a 10 to 12dB reduction in volume was pretty close. This makes me wonder if the sound will be loud enough with the charging case transmitter connected to an inflight entertainment system.
Bottom line: The P17s would look fairly “by the book” if it weren’t tilted down, which shows the treble response will be weak relative to the bass. This will be audible, and those who like plenty of treble (and the subjective sense of detail it lends) may find this sound dull. The noise canceling is pretty good, though.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, July 2021
I measured the ISOtunes Free earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator with the RA0402 high-resolution ear simulator with KB5000/KB5001 simulated pinnae, and a Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. An Mpow BH259A Bluetooth transmitter was used to send signals from the Clio 12 QC to the earphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. Note that my usual impedance and sensitivity measurements are irrelevant for wireless earphones, and impossible to do without disassembling them, and are thus not included here. If you’d like to learn more about what our measurements mean, click here.
The above chart shows the Frees’ frequency response measured with the RA0402 ear simulator. They’re not too crazy—actually, they’re well within sight of “normal.” There’s definitely some bass response lacking below 100Hz, but the total sum of treble energy is right about where it needs to be, although with a little extra zip around 5.5kHz.
This chart shows the Frees’ right-channel response compared with other true wireless earphones: the KEF Mu3s (which are the true wireless earphones I’ve found come closest to the Harman curve), the Status Audio Between Pros, and the Grado GT220s. Other than the relative lack of low bass, the Frees’ response is remarkably similar to that of the GT220s.
The Frees’ spectral-decay (waterfall) response shows notable resonances only at 3 and 5.5kHz, which correspond exactly with the response peaks in the frequency response. As I sometimes see with true wireless earphones, there’s some very high-Q “hash” up in the mid-treble, much as I usually measure with planar-magnetic headphones, but I’m not sure if it’s a measurement artifact, a Bluetooth thing, or an actual acoustical effect, or whether its effects are audible.
The Frees’ distortion is negligible at 90dBA, which is a pretty loud listening level. The highest level I could get out of them is 98dBA (rather than my usual 100dBA measurement), but this seems to push them into clipping. I never heard distortion in my testing, for what it’s worth.
This chart shows the Frees’ isolation with the silicone and foam tips, compared with the Campfire Comet earphones (with foam tips) and the Bose QC Earbuds, which have active noise canceling. The Comets, if I remember correctly, have the best passive isolation of any earphones I’ve measured—until now. The Frees’ isolation in the “airplane cabin noise band” (about 100Hz to 1.2kHz) is better than that of most noise-canceling headphones and earphones. Very impressive.
Latency with the Frees connected to the Mpow BH259A Bluetooth transmitter typically measures about 317ms. That’s about 100ms more than I typically measure with Bluetooth headphones, which suggests these don’t use the latest and greatest Bluetooth chips. So depending on the latency of your display, there’s a good chance you’ll notice lip-sync problems when watching videos.
ISOtunes states that the maximum volume of the Frees is 85dB, although the measurement technique is not specified. Using the same measurement technique I use for Wirecutter’s measurements of kids’ headphones’s measurements of kids’ headphones, I got a maximum of 90.5dBA with -10dBFS pink noise.
Bottom line: The Frees lack some low bass, and—by design—don’t play as loud as most other true wireless earphones I’ve tested, but I see no red flags here. And the passive isolation is really impressive.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, June 2021
I measured the EarFun Free 2 earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator with the RA0402 high-resolution ear simulator with KB5000/KB5001 simulated pinnae, and a Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. An Mpow BH259A Bluetooth transmitter was used to send signals from the Clio 12 QC to the earphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. Note that my usual impedance and sensitivity measurements are irrelevant for wireless headphones, and impossible to do without disassembling them, and are thus not included here. If you’d like to learn more about what our measurements mean, click here.
The above chart shows the Free 2s’ frequency response measured with the RA0402 ear simulator. I did these measurements after I submitted the review text, and was delighted to see that they exactly match my subjective impressions. That peak at 3kHz is pretty much “by the book,” but otherwise, this is a classic “smiley” response, with a big boost in the bass, balanced out with a broad peak between 7 and 11kHz.
This chart shows the Free 2s’ right-channel response compared with other true wireless earphones: the original Frees, the Grado GT220s, and the KEF Mu3s (which are the true wireless earphones I’ve found come closest to Harman curve). This chart makes it clear how boosted the Free 2 earphones are in the bass and the mid-treble.
The Free 2s’ spectral-decay (waterfall) response shows some hashy, super-high-Q resonances between about 7 and 11kHz, which corresponds with the big mid-treble peak in the frequency response. I’m not sure if this is an actual acoustical artifact or a Bluetooth-related artifact, but I see something similar around 2kHz when I measure spectral decay of planar-magnetic over-ear headphones. If it’s audible, my guess is that it creates a sense of “air” rather than the perception of a sonic coloration.
The Free 2s’ distortion is negligible even at the extremely loud level of 100dBA (measured with pink noise).
This chart shows the Free 2s’ isolation in its various modes compared with the original Frees, the Grado GT220s, and the Bose QC earbuds, which have active noise canceling. The Free 2s’ isolation is about in the same ballpark as similar designs.
Latency with the Free 2s connected to the Mpow BH259A Bluetooth transmitter is typically about 217ms. As the BH259A and the Free 2s both have aptX, I assume this is from an aptX connection, but the measurement with SBC should be similar. It’s enough latency to create mild lip-sync problems when watching YouTube videos or playing video games, but that will also depend on the latency of the display you’re using.
Bottom line: The EarFun Free 2 earphones definitely have a smiley response curve, but it’s well-balanced between the bass and treble, and the other measurements look fine.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, June 2021
I measured the Soundcore Life Q35 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were fed signals from an MPOW BH259A Bluetooth transmitter. For some wired measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the Life Q35s’ frequency response in the Soundcore Signature EQ mode and with the Transport noise-canceling mode on. It’s a somewhat Picasso-esque version of the Harman curve, with the sharp rise to a shelved-up bass response (although much more than Harman curve) and a fairly by-the-book rise at 2kHz, but the deep dip between 3 and 4kHz is peculiar, and there’s a lot more high-frequency energy above 8kHz than I’m used to seeing. I’d guess this would sound fairly balanced, but a little weird.
This shows how the sound changes with different EQ modes in the app. (I used pink noise from the AudioTool app, and magnified the Y axis to 5dB per step.) You can see that at least for the modes I selected, the EQ modes mostly select a different amount of output above 200Hz.
This chart shows the Life Q35s’ right-channel response compared with the DALI IO-6 (with NC on), the Marshall Monitor II A.N.C. (NC on, Rock mode), and the AKG K371 headphones (the latter being closed-back headphones that come very close to the Harman curve response). Again, the Life Q35s’ response is flatter than usual. As with the IO-6es, there’s some bass roll-off, but the relatively low level of the treble output should keep the sound balanced.
The Life Q35s’ spectral-decay plot (measured in wired mode) shows a little bit of resonance in the lower frequencies—not surprising considering the fairly large amount of bass boost in the frequency-response curve.
The total harmonic distortion of the Life Q35 headphones (measured here in Bluetooth mode) is negligible at the very loud level of 90dB (level set with pink noise), but at the extremely loud level of 100dBA, it runs a little high in the bass and has a strange spike centered at about 320Hz. Still, it doesn’t get high except down below 40Hz, and there’s not much under-40Hz content in music, so I doubt you’d hear it.
In this chart, you can see how the different noise-canceling modes of the Life Q35s compare. The external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation.
This chart compares the noise canceling of the Life Q35s in the Transport mode against some competitors. It’s world-class, actually better than the more-or-less “reference” noise-canceling headphones, the Bose N700 NCs, between 50 and 200Hz. So they’ll do a great job of eliminating the low-frequency rumble of jet engines.
The Life Q35 headphones’ impedance curve is about as expected for a dynamic-driver-based design, running at an average of roughly 23 ohms with a modest amount of phase shift through the audioband.
In Bluetooth mode, latency measures 208ms with the MPOW BH259A transmitter. This is a typical result with the SBC codec.
Sensitivity, measured between 300Hz and 3kHz, using a 1mW signal calculated for 16 ohms rated impedance, is 98.3dB with the power off. So the headphones will probably play loud enough for you when plugged into an inflight entertainment system, or if the batteries run down.
Bottom line: The Soundcore Life Q35 headphones’ frequency response is somewhat weird, but the noise canceling is fantastic and none of the other measurements suggest any problems.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, May 2021
I measured the DALI IO-4 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were fed signals from an MPOW BH259A Bluetooth transmitter. For some wired measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the IO-4s’ frequency response. This is somewhat flatter than usual, which suggests that they may sound a little elevated in the low- and mid-midrange region.
This chart shows the response in wired mode with power on and off, compared with Bluetooth mode. Not surprisingly, the response is similar with the power on; the wired connection seems to have a little more bass output than the Bluetooth connection. (Note that the Bluetooth measurement is a gated response, because of Bluetooth’s latency, and thus may not be 100% comparable with the measurement in wired mode.) The wired mode boosts the treble, which will probably be heard as a reduction in bass response.
This chart shows the IO-4s’ right-channel response compared with the DALI IO-6 headphones (with NC on), the Marshall Monitor II A.N.C.s (NC on, Rock mode), and the AKG K371s (closed-back headphones that come very close to the Harman curve response). Again, the IO-4s’ response is flatter than usual. As with the IO-6 headphones, there’s some bass roll-off, but the relatively low level of the treble output should keep the sound balanced.
The IO-4s’ spectral-decay plot (measured in wired mode) looks pretty clean, with a mild resonance around 1.9kHz, but it’s well-damped and gone within about two cycles.
The total harmonic distortion of the IO-4 headphones (measured here in Bluetooth mode) is near zero at the very loud level of 90dB (level set with pink noise), but at the extremely loud level of 100dBA, it runs between about 2% and 6%.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. As you can see, the isolation of the IO-4s is comparable to that of other dynamic-driver, closed-back models, like the AKG K371s, and the benefit of the IO-6es’ noise canceling is negligible. I also threw in the open-back HiFiMan Deva headphones, as I mentioned them in the review.
In wired mode, the IO-4 headphones’ impedance curve is surprisingly flat for a dynamic-driver design; it barely deviates from the rated 25 ohms, and shows very little phase shift through the entire audioband.
In Bluetooth mode, latency measures 220ms with the MPOW BH259A transmitter. This is a typical result with the SBC codec.
Sensitivity, measured between 300Hz and 3kHz, using a 1mW signal calculated for 25 ohms rated impedance, is 103.2dB. So these headphones should play pretty loud when plugged into an inflight entertainment system.
Bottom line: The IO-4 headphones measure just like comparable HiFiMan models. Other than the low sensitivity, there are no concerns.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, May 2021
I measured the HiFiMan HE400se headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the HE400se headphones’ frequency response. This is typical of most HiFiMan models, and of open-back planar-magnetics in general—a more or less flat response up to 1kHz, then a broad rise between 2.5 and 9kHz.
This chart shows how the headphones’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop, some tube amps, or some professional headphone amps. Because of the headphones’ almost purely resistive load, there’s almost no change in response as output impedance increases.
This chart shows the HE400se headphones’ right-channel response compared with two other affordable open-back models and the AKG K371s (closed-back headphones that come very close to the Harman curve response). The HE400se headphones’ response is almost the same as the HiFiMan Deva headphones, with a little more energy in the mid-treble, and similar to the Emotiva Airmotiv G1s. The Harman curve headphones have a lot more bass and somewhat stronger output around 2kHz.
The spectral-decay plot (measured in wired mode) for the HE400se’s shows the usual “hash” of very high-Q, low-level resonances in the upper midrange and lower treble, which I believe is caused by comb-filter effects of the sound bouncing back and forth between the flat planar driver and the flat plate of the ear/cheek simulator. The only planar-magnetic models I’ve tested that don’t show this effect are recent models from Dan Clark Audio. Regardless, either it’s sonically insignificant, or maybe it contributes to a greater sense of “air” and spaciousness.
The total harmonic distortion of the HE400se headphones is very low when measured with the Schiit Magnius amp, which is typical of planar-magnetic headphones. Note that when I measured at 100dBA (level set with pink noise) using the Musical Fidelity V-CAN, distortion hit about 20% in the midrange because the amp clipped, due to the headphones’ low sensitivity.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. As you can see, there’s almost no isolation at all; outside sounds pretty much come right in. I included the Audeze LCD2 Closed-Back headphones so you can see how an audiophile closed-back design compares.
Typical of planar magnetics, the HE400se headphones’ impedance curve is almost purely resistive: dead-flat at 26.5 ohms, with very little phase shift through the entire audioband.
Sensitivity, measured between 300Hz and 3kHz, using a 1mW signal calculated for 25 ohms rated impedance, is 86.6dB. (It’s rated at 91dB, test conditions not specified.) So these are definitely in the realm of “amp pretty much required.”
Bottom line: The HiFiMan HE400se headphones measure just like comparable HiFiMan models. Other than the low sensitivity, there are no concerns.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, June 2021
I measured the AKG K72 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the K72s’ frequency response. This looks somewhat “old-school dynamic headphones” to me, with a big, broad hump in the bass balanced out by a large, broad peak in the lower- and mid-treble ranges. By Harman curve standards, there’s about a 5dB excess of energy below 600Hz, which may be the reason I thought these sounded slightly bassy, and about a 5dB deficit from 1 to 4kHz.
This chart shows how the K72s’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop, some tube amps, or some professional headphone amps. There’s no audible difference, which comes as no surprise when you’ve seen the unusually flat impedance curve below.
This chart shows the K72s’ right-channel response compared with two other affordable studio headphones and the HiFiMan HE400se open-back headphones. You can easily see that the K72s are less flat than their competitors, and the deficit of midrange energy is evident.
The K72s’ spectral-decay plot looks clean, with just a bit of resonance in the bass. Maybe that’s what’s giving me the impression of somewhat boosted bass.
Other than an unusual spike centered at 80Hz, distortion of the K72s is modest even at very loud listening levels.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. As you can see, the K72s offer isolation comparable to that of other closed-back models.
As promised in the review, I ran some quick-and-dirty leakage measurements to get a rough idea of how well the K72s live up to their claim of excellent isolation—meaning, in this case, preventing the sound in the headphones from leaking out. To do this, I suspended my Audiomatica MIC-01 measurement microphone 0.3m above the plate of the GRAS ear/cheek simulator; set the level in the headphones at 100dB, using pink noise; then ran a logarithmic chirp tone through the headphones and measured the sound at the microphone. The traces you see on the graph above show how much each frequency of sound leaks out of the different headphone models. I included the K72 and the AKG K371 headphones, as well as the Beyerdynamic T5s and the HiFiMan Sundaras (so you could see how a typical open-back model performs on this test). The leakage of the K72s seems confined enough to prevent significant leakage of sound into recording microphones (depending on the microphone pickup pattern and the output of the instrument), although it’s probably not quite as good as that of the K371s.
The K72 headphones’ impedance curve is surprisingly flat for dynamic-driver headphones, hovering closely around 35 ohms through the entire audioband. Impedance phase shift is mild, maxing out at +20 degrees at 20kHz.
Sensitivity, measured between 300Hz and 3kHz, using a 1mW signal calculated for 32 ohms rated impedance, is 99.2dB. That’s well below the rated 112dB, but still efficient enough that the K72s can deliver reasonably loud volume from mobile devices that have headphone jacks.
Bottom line: For most listeners, the K72s won’t sound as natural and neutral as the K371s, but they’re a third of the price! And from a technical standpoint, there’s nothing seriously amiss here.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, May 2021
I measured the Bowers & Wilkins PX7 Carbon Edition headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. An Mpow BH259A Bluetooth transmitter was used to send signals from the Clio 12 to the headphones. For wired measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the PX7 Carbon Editions’ frequency response in three modes: Bluetooth with noise canceling on and with noise canceling off, plus wired mode with noise canceling off. A couple of notes here. This is an unusual response—while the bass looks almost Harman curve-ish, there’s an unusual peak around 1kHz, the usual peak at about 2 to 3kHz is muted by a few dB, and the peak up around 8 to 9kHz is maybe 6dB higher than I might usually see. There’s a big difference in response with noise canceling off—a lot less bass, mainly—but very little difference between the wired and Bluetooth connections.
This chart shows the PX7 Carbon Editions’ right-channel response (all modes activated) compared with two other noise-canceling headphones (with NC on) and the AKG K371s (headphones that come very close to the Harman curve response). It looks like the PX7 Carbon Editions will have a deficit of lower treble and a surplus of mid-treble, relative to most other headphones.
Any resonances the PX7 Carbon Editions might have are well-damped and not troublesome—except for that super-high-Q one at 3kHz, but it’s way too narrow to hear.
The total harmonic distortion (measured in wired mode with power on) of the PX7 Carbon Editions shows an unusual 6% peak at 200Hz, which would appear as harmonics at 400Hz, 600Hz, etc., so it might be audible if you’re playing the headphones very loud. There’s a relatively high amount of distortion in the bass, too, but audibility of distortion is much lower at bass frequencies because your ear isn’t very sensitive there, so I doubt you’d notice it.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. The isolation of the PX7 Carbon Editions (shown here in Auto mode) is not impressive; it’s about the same as the DALI IO-6es achieve, and those weren’t impressive on this test, either. Maybe the Auto function would work better on an actual airplane? I’m not sure and it’ll be a while before I get on one of those again . . .
In wired mode, the PX7 Carbon Editions’ impedance magnitude runs mostly above 1500 ohms, which is the measurement limit of the Clio 12 analyzer. That’s to be expected of active headphones; as best I could tell, the power always switches on when the cable is plugged in, so there doesn’t seem to be a fully passive mode. I got 98.8dB average when I measured the sensitivity of the wired connection (calculating the drive voltage for the default 32 ohms impedance, which I usually do with active headphones).
Bluetooth latency of the PX7 Carbon Editions used with the Mpow BH259A transmitter is 220ms. That’s typical of SBC, although the PX7 Carbon Editions are said to be equipped with the standard, Adaptive, and HD versions of Qualcomm aptX. The BH259A has standard aptX and aptX HD, so I’m surprised I didn’t get a lower latency here.
Bottom line: Bowers & Wilkins definitely went their own way with the PX7 Carbon Edition headphones. Their frequency-response curve is unusual (although not as weird as the Yamaha YH-E700A headphones I recently tested), and at least in my tests, the noise canceling didn’t seem impressive. But while they’re outside the norm, I’d guess the unusual aspects of the frequency response aren’t so extreme that they’d make these sound bad or weird.
. . . Brent Butterworth
brentb@soundstagenetwork.com
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