I measured the NuForce HEM8s using a G.R.A.S. Model RA0045 ear simulator (plus a Model 43AG ear/cheek simulator for isolation measurements), a Clio 10 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. I used one of the supplied silicone eartips because it best fit the RA0045. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The HEM8s’ frequency response is unusual: I can’t recall seeing another earphone with such a strong and dominant peak at 10kHz. Typical earphones have a strong peak (often 10dB or so) in the 3kHz region, and more of an emphasis in the 6-8kHz range.
This chart compares the HEM8s’ response with a silicone eartip and a Comply foam tip. The Comply tip slightly reduces overall sensitivity (perhaps it holds the soundtube slightly farther away from the RA0045’s internal microphone), and also reduces the treble by about 2dB at frequencies above 9kHz.
Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has a large effect on the HEM8s’ frequency response, with a large boost in the bass that averages 7dB. The output impedance of the source device tends to have a big effect on the frequency responses of balanced-armature earphones, but in this case that effect is extreme.
On this chart, the HEM8s (blue trace) clearly have a mellower, softer treble than the Klipsch Reference X20i (green) and the PSB M4U 4 (red), two other multidriver earphones using at least one balanced armature per ear.
The HEM8s have a clean spectral-decay (waterfall) plot, with no noteworthy resonances.
The total harmonic distortion (THD) of the HEM8s is low, barely hitting 2% even with the extremely high signal levels I use for this test.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The HEM8s’ isolation is very good, largely because its body fits so deeply and securely into the ear. In this case, the Comply eartips improve isolation by 1-3dB in the “jet engine band” of 50-200Hz.
Like most earphones using balanced-armature drivers, the HEM8s have a large impedance swing, running from a high of 41 ohms at 20Hz to between 7 and 9 ohms at frequencies above 800Hz. This is the reason for the large effect of source impedance on the HEM8s’ frequency response. An accompanying phase shift in the transition region maxes out at -55° at 434Hz.
The sensitivity of the HEM8s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified 37 ohms impedance, is extremely high at 117.0dB. Any source device should be able to drive these earphones to loud levels.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the N60 NCs using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 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. In most cases, I used the clamping mechanism on the Model 43AG to ensure a good seal of the earpads against the simulator’s fake rubber pinna. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The N60 NCs measure somewhat like typical audiophile open-back, over-ear headphones, with a flat response to about 1.3kHz and, above that, strongly rising upper-midrange and treble responses. This suggests that their sound will probably thrill discriminating listeners who like a fairly even response, but will grate on those who prefer lots of bass.
You can see from this chart that the N60 NCs’ frequency and tonal balances don’t vary a lot when the noise-canceling is switched off. Yes, there’s less bass, but there’s also less treble; the tonal balance should sound fairly similar either way.
Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has no significant effect on the N60 NCs, either in passive mode (shown here) or noise-canceling mode.
This chart shows that the N60 NCs are clearly voiced differently from two other well-known noise-canceling headphones, the Bose QC25s and the PSB M4U 2s. The AKGs’ response in the range between 1.3 and 4.5kHz is much stronger than either competitor, although the M4U 2s have a stronger response from 7 to 10kHz.
The N60 NCs’ spectral-decay (waterfall) plot shows a very clean response, with only extremely narrow, weak resonances at a few higher frequencies, and a much tighter (nonresonant) bass response than I’m used to seeing.
The total harmonic distortion (THD) of the N60 NCs is very low, even at the very loud levels used for this measurement. This measurement was in active mode; distortion was even lower in passive mode.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The measurement of the N60 NCs’ noise-canceling mode shown here is the average of the measurements with the ear/cheek simulator’s clamp engaged and disengaged. The isolation is actually a little above average in the “jet engine band” of 50-300Hz, averaging about -20dB.
As expected, the impedance of the N60 NCs with noise canceling on (in which case the signal is routed to the amplifier input) runs above 1kHz through most of the audioband. In passive mode, it’s flat at 36 ohms up to 3.5kHz, then dips slightly, to 32 ohms, in the treble. Phase shift is negligible in both modes.
The N60 NCs’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 32 ohms impedance, is 107.0dB in passive mode, 107.5dB in noise-canceling mode, making the N60 NCs one of only a few noise-canceling headphones that don’t suffer a huge reduction in volume when their batteries run down
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Sphears using a G.R.A.S. Model RA0045 ear simulator, a Clio 10 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. I used one of the supplied silicone eartips because it fit the RA0045 best, and because I used silicone tips for most of my listening. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The frequency response of the Sphears has a somewhat higher ratio of mid-treble (6-10kHz) to lower treble (ca 3kHz). Most earphones I’ve measured have a more prominent peak around 3kHz, and less energy above that. There’s a little less bass than I often see, but the more reserved 3kHz peak subjectively balanced that out.
Adding 70 ohms of output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp has no significant effect, boosting bass by less than 1dB at 20Hz.
Here the Sphears (blue trace) seem to have a tonal balance similar to that of the Sony XBA-H1s (red trace). The RBH EP3s exhibit substantially more bass, but also a lot stronger output between 2.6 and 6.5kHz, which is probably why I found them to sound brighter than the other two.
The Sphears have a very clean spectral decay (waterfall) plot, with no noteworthy resonances.
The total harmonic distortion (THD) of the Sphears is almost nonexistent, even at the very high signal levels I use for this test. This low distortion may be part of what made their sound so unfatiguing.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The Sphears’ isolation is weaker than I’d expected, given their exceptional fit -- but, of course, they fit my ears differently than they fit the simulator.
The Sphears’ impedance is almost perfectly flat in phase and amplitude throughout the audioband.
The sensitivity of the Sphears, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 16 ohms impedance, is 104.1dB. This confirms what I found in my listening: that they delivered satisfying volume levels from any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the HD 800 S headphones using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and Musical Fidelity V-Can and Rane HC6S headphone amplifiers. I moved the headphones around to several different locations on the ear/cheek simulator to find the one with the most bass and the most typical average response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the HD 800 Ses’ frequency response, which is typical for high-end open-back headphones: basically flat up to 1.5kHz, then rising to peaks at 2.7, 6, and 7.7kHz. That’s normal -- most good headphones have response peaks in these regions, and the one at 2.7kHz, in particular, is generally thought to help headphones deliver a more convincing illusion of hearing freestanding speakers in a room.
Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp (which I can’t imagine anyone doing with these headphones) boosts the HD 800 Ses’ output between 30 and 300Hz by an average of about 1.5dB, which will make the headphones sound just slightly more full.
This chart compares the frequency response of the HD 800 Ses with two similarly priced open-back models: the HiFiMan Edition Xes and the Audeze LCD-Xes. Obviously, all three are much more alike than they are different, the HD 800 Ses roughly splitting the difference in the treble between the Edition Xes and the LCD-Xes.
The HD 800 Ses’ waterfall plot shows some extremely narrow, low-level (-40dB) resonances between 1 and 4kHz. These are fairly common with open-back headphones. When I measure open-back headphones, I pile denim insulation on top of them to minimize the leakage of sound into the room (where it could reverberate) and/or back into the headphones, so I don’t think these are room effects or leakage of outside sounds into the measurement.
The HD 800 Ses’ total harmonic distortion (THD) is unusually low except below 100Hz, where it’s higher than average. When I saw these results, and how smoothly the distortion increases with frequency, I thought the Musical Fidelity V-Can might be having a problem driving the HD 800 Ses’ unusually high impedance. So I switched to a Rane HC6S, a professional studio headphone amp that, by my measurements, puts out 3.1W into 32 ohms and 0.4W into 250 ohms. I got the same results with the Rane. By my measurements and calculations, the HD 800 Ses should have needed only 2.7mW to achieve the needed 20Hz output at the 100dBA measurement level, which is well within both amplifiers’ capabilities; it appears these headphones’ measured bass distortion at very high listening levels is indeed higher than normal. But despite listening at fairly high levels -- which I often do with high-quality headphones because they generally don’t fatigue my ears -- I heard no distortion.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. Like all open-back headphones, including the others represented here, the HD 800 Ses offer no significant isolation from outside sounds. I include the Audeze LCD-Xes’ isolation measurement so that you can see how the HD 800 Ses compare with a closed-back model.
The impedance magnitude of the HD 800 Ses is very high and above the specified 300 ohms, running from a low of 339 ohms to a high of 801 ohms. The impedance phase curve is reasonably flat, though not as flat as those of many high-end planar-magnetic headphones I’ve measured.
The sensitivity of the HD 800 Ses, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified 300-ohms impedance, is 103.0dB. That’s high for high-end open-back headphones, but portable players and smaller headphone amps may still be unable to muster the additional 9.7dB of voltage output required to drive 300-ohm headphones, compared with typical 32-ohm models.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the RBH Sound HP-2s using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 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. I moved the headphone around to several different locations on the ear/cheek simulator to find the one with the most bass and the most typical average response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the HP-2s’ frequency response, which suggests that their tonal balance will be fairly neutral. It’s a fairly by-the-book response, with nothing to indicate that these headphones will have major idiosyncrasies. There’s perhaps a little more energy than usual between 7 and 10kHz, but the peak between 2 and 3kHz is at a typical level relative to the bass and midrange, which is probably why I found the headphones’ treble emphasis subtle and unobjectionable.
Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has only a subtle effect on the HP-2s’ response, kicking up the bass below 60Hz by about 1dB.
This chart compares the HP-2s with three other midpriced closed-back models: the NAD Viso HP50s, the Oppo Digital PM-3s, and the Bowers & Wilkins P7s. The response of the HP-2s is pretty close to that of the Viso HP50s, with a little more bass and a somewhat bigger peak between 2 and 3kHz.
The HP-2s’ waterfall plot looks clean above 1kHz, with no significant resonances. The resonance visible in the bass is typical of closed-back headphones.
The total harmonic distortion (THD) of the HP-2s is generally low. It gets up to around 1.5% in the bass at the very loud listening level of 90dBA. That’s probably inaudible -- a subwoofer routinely hits higher numbers in normal use without producing audible effects. Distortion exceeds 4% in the bass at the extremely high level of 100dBA, a typical result for closed-back headphones of the HP-2s’ size and price.
In this chart, the level of external noise is 75dB SPL (red line); the numbers below that indicate the level of attenuation of outside sounds. Here, the HP-2s achieve essentially the same result as their competitors. For reference, I added the result from the Bose QC25s, which have the most effective noise canceling of any over-ear headphones now on the market.
The impedance magnitude of the HP-2s is pretty much flat, running between 35 and 40 ohms; the impedance phase is also essentially flat.
The sensitivity of the HP-2s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 32 ohms impedance, is 106.6dB. That’s high -- you won’t have any problem getting adequate volume from any source device I know of.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Audeze iSine10s using a G.R.A.S. Model RA0045 (with a Model 43AG ear/cheek simulator for isolation measurements), a Clio 10 FW audio analyzer, and a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most of these measurements, I used a Musical Fidelity V-Can headphone amplifier and the analog cable because, like most audio analyzers, the Clio needs to use its own test signals for most measurements, and I currently have no way to send those signals through a Lightning connection. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.
The iSine10s’ frequency response with a passive connection was flatter than that of most earphones I’ve measured, and more like that of typical planar-magnetic over-ear headphones. Their upper-midrange response peak (a characteristic found in most good headphones) is centered on the unusually low frequency of 1.5kHz; usually, this peak is centered somewhere between 2 and 4kHz.
This chart shows how the iSine10s’ measured response changes when the Cipher cable is used. (This measurement was taken with pink noise, with the EQ in the iOS app at its default setting of Flat.) A large peak is introduced at 3kHz, and the mid-treble region is elevated by 8 to 12dB. The blue curve shows my best attempt at matching the response with the Cipher cable to the passive response. This difference is intentional; Audeze says it uses the DSP in the Cipher cable so that the iSine10s’ response will better match the responses of the company’s open-back, over-ear headphone models.
This chart shows the results of adding 70 ohms of output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp. It shows that the iSine10’s response is, for all intents and purposes, unaffected by the output impedance of the source device.
This chart shows the iSine10s’ measured right-channel frequency response compared with two high-quality earphone models I’ve previously tested: Audiofly’s AF1128 and PSB’s M4U 4. Just out of curiosity, I also included the response curve of Audeze’s LCD-X over-ear headphones. It’s interesting to see how close the iSine10s’ response without DSP is to the LCD-Xes’; the only major difference is that the iSine10s’ upper-midrange response peak is centered at 1.5kHz instead of the LCD-Xes’ 2.5kHz. The bass and treble peaks in the M4U 4s’ curve reflect a response more like that of most earphones I’ve measured.
The spectral-decay (waterfall) chart shows a little bit of resonance at 1.2kHz, but this is at about -20dB and dies out quickly, in about 5ms. Those extremely narrow, low-level resonances between 5 and 10kHz are common in planar-magnetic headphones, though they’re usually at lower, more readily audible frequencies.
The total harmonic distortion (THD) of the iSine10s was the lowest I can recall measuring. Even at extremely loud levels, there was no audible distortion.
In this chart, the sound-pressure level (SPL) of external noise is 75dB; the numbers below that indicate the degree of attenuation of outside sounds. For comparison, I’ve included the isolation plots of the Audiofly AF1128 high-end earphones with over-ear cable routing, NAD Viso HP20 conventional earphones, and Bose’s noise-canceling QC20 earphones. Because of their unique open-back design, the iSine10s offer the least isolation of any earphones I’ve measured; they’ll let through almost all of the sounds around you.
The iSine10s’ impedance is dead flat at 16 ohms (same as the specification), and its electrical phase is as flat as it gets.
The sensitivity of the iSine10s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified impedance of 16 ohms, is 106.7dB. That’s above average, meaning that the iSine10s will play loudly from practically any source device -- although their lack of isolation from external sounds could mean that they’ll sometimes need to play a lot louder than usual.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Pryma 0|1s using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 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. I moved the headphones around to several different locations on the ear/cheek simulator to find the position with the most bass and the most typical average response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the Pryma 0|1s’ frequency response, which looks largely flat, with perhaps a tad of extra bass, a little extra energy around 1kHz, and a little less energy around 3kHz than we usually see.
Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp reduces the Pryma 0|1s’ upper bass very subtly: about 1dB between 80 and 240Hz.
This chart compares the Pryma 0|1s with three well-regarded closed-back competitors: NAD’s Viso HP50s, Bowers & Wilkins’s P7s, and Oppo Digital’s PM-3s. The Pryma 0|1s have the most downward-tilted (i.e., more bass, less treble) balance of any other of the headphones shown. Note that a flat measured response in headphones does not necessarily result in a flat perceived response, as it generally does with loudspeakers.
Other than a somewhat strong resonance centered at 950Hz, the Pryma 0|1s’ waterfall plot looks pretty clean.
The Pryma 0|1s’ total harmonic distortion (THD) is a little higher than average at low frequencies. At the loud listening level of 90dBA, the THD hits about 1% at 100Hz, and 5% at 20Hz. At the extremely loud level of 100dBA (included more as a benchmark than as a representation of anything you’ll encounter in actual listening), it hits about 3% at 100Hz and 9.5% at 20Hz.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the attenuation of external sounds. That the Pryma 0|1s offer 5-10dB less isolation than many other closed-back headphones (including the B&W P7s, PSB M4U 1s, and Oppo PM-3s, all shown here) is probably due to their relatively small earpieces.
The impedance magnitude of the Pryma 0|1s averages about 35 ohms, and the impedance phase is nearly flat.
The sensitivity of the Pryma 0|1s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 32 ohms impedance, is very high at 107.4dB -- any source device or headphone amplifier can drive them.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Blue Ellas using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, a Musical Fidelity V-Can headphone amplifier, and an Audio-gd NFB-1AMP amplifier for the distortion measurements. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The Ellas’ frequency response is unusual in two ways. Judging from the right-channel response, it’s flatter than usual, with a much narrower peak in the 3kHz area than I’m used to seeing. The other unusual thing is that the response of the left channel doesn’t match that of the right. I tried reseating the left earcup many times, and even repeated my measurements a week later, but couldn’t get a closer match than is seen here. It could be because the left channel’s acoustics are different from the right’s. I’ve seen this before in active headphones, and assume that it’s because of the space consumed by the battery in one earpiece. It’s worth noting that in Blue’s first headphones, the Mo-Fis, which share the Ellas’ basic design and are also internally powered, the channels were much better matched.
This chart shows the Ellas’ frequency response in passive, active, and + (bass boost) modes. The response in active mode is the same as in passive, but the level in passive mode is 8.1dB lower. The response in + mode shows a bass boost about two octaves wide, centered at 65Hz.
This chart shows the results of adding 70 ohms of output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp. Only the results in passive mode are shown, because in active mode the impedance of the source component doesn’t affect the response. Using a higher-impedance source has only a barely measurable, probably inaudible effect on the Ellas’ response.
This chart shows the Ellas’ measured right-channel frequency response compared with that of Oppo Digital’s PM-3s -- like the Ellas, one of only a few closed-back planar-magnetic headphones available -- and NAD’s Viso HP50s, my comparison standard for midpriced closed-back headphones. Out of curiosity, I also included Blue’s original headphones, the Mo-Fis, which have dynamic drivers instead of the Ellas’ planar magnetics. The Ellas have more or less the flattest measured response of the bunch, though that doesn’t necessarily mean they’re the flattest-sounding.
The spectral-decay (waterfall) chart shows a resonance only at around 500Hz, though overall there’s less bass resonance than I usually see in these charts.
The total harmonic distortion (THD) of the Ellas was higher than I’m used to measuring. At 90dBA, the THD is low above 50Hz, and of course most music has little content below 50Hz. The THD gets very high below 60Hz at 100dBA, but this is an extremely loud level that few people would want -- or be advised -- to listen to for more than a few seconds. I repeated this measurement a week later with a fresh calibration and got essentially the same result. The measurements were roughly the same in passive and active modes, so this distortion is apparently coming from the driver.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. For comparison, I’ve included the isolation plots of the Oppo Digital PM-3s (a closed-back planar magnetic design), the NAD Viso HP50s (a closed-back dynamic design), and the noise-canceling Bose QC25s. The Ellas’ isolation is below average for a closed-back design, though they do attenuate the upper mids and treble by 14-19dB.
The Ellas’ impedance in active mode, while specified as 10 ohms, is actually beyond my Clio analyzer’s limit of 1500 ohms. (The Clio is designed to measure the impedance of speakers, not electronics.) In passive mode, it’s flat at 54 ohms, with almost perfectly flat phase response. Electrical phase varies more in active mode, but this shouldn’t affect the Ellas’ sound.
The sensitivity of the Ellas, measured between 300Hz and 3kHz with a 1mW signal, was 95.8dB in passive mode (calculated for the specified 50 ohms passive impedance), 95.3dB in active mode (calculated for the specced 10 ohms active impedance). Note that because these sensitivity measurements are calculated for different headphone impedances, they use different signal voltages -- 0.22V for 50 ohms, 0.1V for 10 ohms -- and thus are not comparable. In my frequency-response measurements, cited above, I found that switching to active mode boosts the Ellas’ output by 8.1dB with the same test-signal voltage. In either mode, though, the Blues’ sensitivity was a little lower than average; the Ellas should play loud enough in active mode, but passive mode might be a little too quiet to reach satisfying levels with some music in some environments.
. . . Brent Butterworth
brentb@soundstagenetwork.com
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