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
Reviewed on: SoundStage! Solo, April 2021
I measured the YH-E700As 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 YH-E700As’ frequency response in Bluetooth mode with noise canceling, Listening Optimizer, and Listening Care are all activated, which I assume is the way most people will usually listen to these headphones. This is a strange-looking response at just about every frequency range. First, the bass is clearly elevated relative to the rest of the audio range. Second, there’s an unusual bump in the midrange around 500Hz. Third, the rises in response we normally see between 2 and 6kHz, which help headphones produce a sound and spatial presentation somewhat closer to that of speakers in a real room, are mostly absent. Fourth, there’s a lot more output above 10kHz than we normally see, although at present we have no research on what constitutes the “right” top-octave response in headphones because the equipment to do useful measurements in this range has become available only in the last two or three years. Fifth, no matter what I tried, I couldn’t get the response from the two channels to match well.
Here we can see the effect of the different listening modes: noise canceling, Listening Optimizer, and Listening Care. (Note that the Y-axis resolution is doubled so you can see the differences more easily. I also had to do this measurement by playing pink noise from my Samsung Galaxy S10 phone, so I could activate the modes using Yamaha’s Android app.) At least on the ear/cheek simulator, there’s not much difference among the different modes. Noise canceling produces a 3-to-5dB drop between 100 and 200Hz, and a 1.5-to-2dB boost between 300 and 500Hz, but otherwise, these modes seem to have little effect on the sound, which squares with my listening impressions.
This chart shows how the Yamaha YH-E700A earphones’ tonal balance changes when they’re used in wired mode rather than Bluetooth mode (with all sound modes activated). The wired mode looks a little more like a normal headphone response, although the headphones go from having a deficit of response at 200Hz in BT mode to an overabundance of energy at 200Hz in the wired mode. We do see a narrow peak at 5kHz; if that were accompanied by a broader peak in the 2-to-3kHz range, we’d start to see (and hear) a typical headphone response.
This chart shows the YH-E700As’ 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). I’ve already made detailed commentary above about the YH-E700As’ response anomalies, but this chart makes them even more obvious.
The YH-E700As’ spectral-decay plot (measured in wired mode) shows no significant resonances.
The total harmonic distortion (measured in wired mode) of the YH-E700As is generally low except in the bass, where it rises to about 8% at the extremely loud level of 100dBA. But good news—audibility of distortion is much lower at bass frequencies because your ear isn’t very sensitive there, which is why the threshold of audibility of subwoofer distortion is generally recognized to be about 10% THD.
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 YH-E700As is not bad; it’ll reduce the low droning of jet cabin noise by about 10dB, which is a useful amount (although you’ll still hear some noise). It doesn’t offer the extreme low-frequency noise canceling of the Bose N700 NC earphones, but without the Bose’s steep filter limiting the noise canceling to below 1kHz to eliminate feedback, there’s little chance the YH-E700As will produce eardrum suck.
In wired mode, the YH-E700As’ impedance magnitude is fairly flat, running between 20 and 24 ohms, and the impedance phase angle is also mostly flat.
Sensitivity of the YH-E700As in wired mode, measured between 300Hz and 3kHz, using a 1mW signal calculated for 32 ohms rated impedance, is 102.5dB, so they should play reasonably loud from almost any typical source device.
Bluetooth latency of the YH-E700As used with the Mpow BH259A transmitter is 245ms. This is puzzling to me, because the YH-E700As have aptX Adaptive, which I assume is compatible with standard aptX (which has typical latency around 125ms) and aptX Low Latency (typical latency around 35ms). The BH259A transmitter has aptX Low Latency, so I would expect to get a low-latency response from the YH-E700As. Perhaps an e-mail to Qualcomm is in order . . .
Bottom line: The YH-E700A earphones have a strange frequency-response curve, and the Listening Optimizer mode doesn’t seem to do much, if anything, to push it toward a more standard response. My measurements suggest that these headphones will not produce what we think of as a natural-sounding response. If you try these and like them, fine, but I tend to steer people toward headphones designed in accordance with scientific research and standard industry practice.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, April 2021
I measured the KEF Mu3 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 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 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 Mu3s’ frequency response measured with the RA0402 ear simulator. The most interesting thing to see here is in the lower-midrange and bass response, which starts to rise below about 200Hz, rather than below 500Hz as in most earphones. This response corrects for the lower-midrange boominess and bloat generally noted in earphones and headphones, and which the Harman curve corrects.
This chart shows the Mu3s’ right-channel response compared with other true wireless earphones (Technics EAH-AZ70Ws and Status Audio Between Pros), as well as with the AKG N5005s, the passive earphones said to best reflect the Harman curve. The Mu3s track the Harman curve more closely than any other earphones I’ve measured, other than the N5005s, although the KEFs have a little less energy at 2kHz and more between 5 and 7kHz.
The Mu3s’ spectral-decay (waterfall) response shows no significant resonances.
The Mu3s’ distortion is very low at the loud level of 90dBA (measured with pink noise), and barely any higher at the extremely loud level of 100dBA.
This chart shows the Mu3s’ isolation in its various modes (ANC on, ANC off, Ambient) versus two other true wireless models with ANC—the Technics EAH-AZ70W and the 1More EHD9001TA earphones, both of which have excellent noise canceling. The results with the KEFs’ ANC are strange, but correspond with what I heard. Rather than focusing on noise in the band between about 100 and 500Hz—where most airplane cabin noise resides and where ANC tends to be most effective—the Mu3s’ noise canceling is most effective above 300Hz. It doesn’t appear to me that much engineering effort was put into the Mu3s’ noise canceling.
Latency with the Mu3s connected to the Mpow BH259A Bluetooth transmitter is 243ms. In this case, the SBC codec is used because the BH259A doesn’t have AAC, but AAC works much the same way as SBC and should have similar latency. The latency seen here is enough to create 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 Mu3 earphones have generally excellent measured performance, with low distortion and resonance, and a frequency response clearly shown to correlate well with listener preferences. However, if you are a frequent traveler (or expect to return to frequent travel) and want noise-canceling earphones to fly with, I’d recommend you look elsewhere.
. . . Brent Butterworth
brentb@soundstagenetwork.com
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