I measured the Reference X20i’s 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 medium-sized eartips (not the Super-Slim tips) because it’s what best fit the simulator. (The simulator has a round canal, not an oval canal like a real human ear.) This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the frequency response of the X20i’s -- a very typical, by-the-book response curve for earphones, suggesting that the X20i’s will have a fairly neutral sound.
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 a huge effect on the Klipsches’ sound. The greater the output impedance of your source device, the more the X20i’s will tilt toward a trebly sound. This characteristic is typical of headphones using balanced armatures, but this is one of the more extreme examples I’ve seen.
This chart confirms what I stated above: the X20i’s have a very standard response. Here they’re compared with the PSB M4U 4s, the NuForce Primo 8s, and the Shure SE846s: all high-end earphones having balanced armatures or a combination of balanced armatures and dynamic drivers. It’s important to note that all of these headphones have a fairly neutral sound, which is reflected in the relatively even amounts of bass and treble shown in the chart.
Resonance in the X20i’s is generally mild; you can see the usual bass resonances, and also, at 10kHz, an unusual resonance of very low amplitude (approximately -40dB) and very narrow bandwidth that is nonetheless poorly damped. It’s hard to imagine, given the frequency, amplitude, and bandwidth of the resonance, that anyone could hear this other than an expert listener using test tones.
The total harmonic distortion (THD) of the X20i’s is pretty low, at 90dBA (measured with pink noise) -- a very loud listening level. At 100dBA -- an extremely loud level I include not because it applies to real-life listening but because it’s a hurdle some headphones can clear and some can’t -- the X20i’s exhibit significant distortion: 5-10% between 2 and 4kHz. You can probably hear that, but if you listen for long at 100dBA you won’t be hearing much for long.
In this chart, the external noise level is 75dB SPL (red line); the numbers below that indicate the attenuation of outside sounds. The X20i’s’ isolation (orange trace) is typical, at least when measured by the simulator and compared with the RBH EP3s (green) and PSB M4U 4s (purple). If the Super-Slim eartips are as good as Klipsch says, they should improve the isolation in an actual human ear canal.
The X20i’s exhibit a huge impedance swing, going from a low of 24 ohms at 20Hz to a high of 300 ohms at 8.7kHz. This, along with the accompanying large shift in impedance phase, is why the sound changes so much with higher-impedance sources.
The sensitivity of the X20i’s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 50 ohms impedance, is 111.9dB, which is extremely high -- you can get very loud levels from the X20i’s with any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Definitive Technology Symphony 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 on the ear/cheek simulator to find the position that produced the most bass and the most characteristic response. As I usually do with on-ear ’phones, I used the Model 43AG’s clamping mechanism to ensure a good seal. This was a “flat” measurement; no diffuse-field or free-field compensation curve was employed. For all measurements, I used a cabled connection; adding a Bluetooth transmitter introduces latency and thus requires gating, which introduces anomalies into the measurements.
This chart shows the Symphony 1s’ frequency response with noise canceling (NC) on. It’s unusual in that the bass response keeps rising all the way down to 10Hz. Also, most of the measurements of closed-back headphones that I’ve taken show more energy between 100 and 500Hz. I’m not sure if this is good or bad, but these two attributes do suggest that the Symphony 1s’ bass might sound a little unusual. This chart represents the best channel matching I could achieve, but I rarely take points off on this because the positioning of the earpiece on the simulator has such a big effect on the measurement.
This chart shows the frequency response of the Symphony 1s in their three wired listening modes: passive (power off), active (power on, no NC), and NC. Obviously, the sound changes significantly from passive to active to NC modes, but this is common among headphones with these options, and with many, the differences are larger. Active mode seems to have more bass resonance (“hump”) than NC mode, and a little more treble response. That’s surprising, because the bass sounds substantially more prominent in NC mode. It’s likely that the extra treble in active/no-NC mode makes the sound thinner than in NC mode.
Adding 70 ohms of output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amplifier, had no measurable effect in the Symphony 1s’ NC or powered mode (which is why I don’t show it here), but in passive mode it boosted the bass by 2-3dB and the treble by about 1dB, effectively increasing the Symphony 1s’ midrange dip.
This chart compares the Symphony 1s with two other noise-canceling headphones -- Bose’s QC25s and PSB’s M4U 2s -- all with NC on. The Boses are widely considered the market leader in noise canceling, and the PSBs have won nearly universal praise for their sound quality. The big difference is that the DefTechs have a midrange dip of 5-10dB between 700Hz and 2.3kHz. Don’t be too quick to condemn them for this -- lots of well-regarded headphones show a similar midrange dip.
The Symphony 1’s waterfall plot, shown here with NC on, reveals a few minor resonances between 2.5 and 10kHz, but these are well damped, and die out in just a few milliseconds.
The Symphony 1s’ total harmonic distortion (THD), shown here with NC on, is insignificant.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. For reference, the drone of jet-engine noise in an airliner cabin is typically between 50 and 200Hz. For comparison, I’ve included in this chart the measurements of the PSB M4U 2 and Bose QC25 headphones. With NC on, the Symphony 1s’ isolation is about average for NC headphones.
As is usual with active headphones, the Symphony 1s’ impedance is high in powered/NC mode, though from this test I often see impedances of 1000 ohms or more. In passive mode, the DefTechs’ impedance runs between 30 and 60 ohms with a bit of phase shift, which is why the response changes with high-impedance sources in passive mode.
The sensitivity of the Symphony 1s, measured between 300Hz and 3kHz with a 1mW signal and calculated for 32 ohms impedance (my default when measuring powered headphones), is 94.7dB in passive mode, 105.2dB in active mode (NC on). Thus, when their battery runs down, the Symphony 1s will likely play reasonably but not very loud with a smartphone or tablet used as the source.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the RBH Sound EP3s 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 primarily used one of the smaller Comply foam eartips supplied with the EP3s because it fit the simulator well, and I figure it’s what most listeners will prefer. For comparison, I also include a measurement taken with one of the supplied silicone tips. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This is the frequency response of the EP3s using the smaller of the supplied Comply foam eartips. There’s a little more bass and treble output (or a little less midrange output) than I’m used to seeing.
This chart shows the EP3s’ frequency response with the Comply foam tip (green trace) and the medium-size silicone tip (purple trace). The slight difference is perhaps enough to cause the EP3s to sound slightly brighter with the silicone tip. Because the shapes and sizes of ear canals vary, so may the actual results you get with these tips.
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 zero audible effect on the sound of the EP3s.
You can see from this chart that the EP3s (blue trace) have stronger bass and treble output than RBH’s EP1s (red trace), and that both have much less midrange energy than the PSB M4U 4s (green trace). The Sennheiser IE 800s -- which I included because they’re well-regarded earphones that also have ceramic enclosures -- have much less lower-treble response, but a stronger 10kHz response than any of the other headphones measured here.
Resonance in the EP3s is mild and well damped, other than the bass resonances that have shown up in almost every set of earphones I’ve measured.
The EP3s’ total harmonic distortion (THD) is low. At the loud listening level of 90dBA, the distortion will almost certainly be inaudible. A narrow THD peak at 2.7kHz rises to about 3.5% at 100dBA, but it’s probably not troublesome, considering that: 100dBA is way louder than most people would ever listen; the peak is narrow; and the first three distortion products will be at the high frequencies of 5.4, 8.1, and 10.8kHz.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The EP3s’ isolation is fantastic with the supplied eartips of Comply (shown) or silicone (not shown, but almost exactly the same result). They reduce ambient noise in the “jet-engine band” of 100-200Hz by 17-20dB -- better, even, than most noise-canceling headphones can achieve.
The EP3s’ impedance magnitude is essentially flat at 16 ohms, as is the phase.
The sensitivity of the EP3s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 16 ohms impedance, is 105.2dB, which is above average; the EP3s should play quite loudly, regardless of the source device used.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Viso HP30s 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 used the clamping mechanism on the ear/cheek simulator to ensure a good seal (as I always do with on-ear models), and moved the headphone around to several different locations on the simulator plate to find the one with the most bass and the best average of midrange and treble responses. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the HP30s’ frequency response, which is fairly flat. There’s a mild dip in the midrange, which I believe has something to do with the RoomFeel voicing (and anyway isn’t uncommon in headphones), plus a broad, relatively mild peak centered at 3.5kHz. In most of the headphones I measure, this peak -- which is intended to make headphones sound more like speakers in a room -- is narrower, higher in magnitude, and a little lower in frequency.
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 shows a broad boost below 80Hz that maxes out at +1.5dB. It might barely be audible, but certainly wouldn’t be objectionable.
This chart compares the HP30s (blue trace) with NAD’s Viso HP50 over-ear (red) and Beyerdyamic’s T 51 p (green) and Bowers & Wilkins’ P3 (orange) on-ear models. These curves are normalized to 500Hz, which is near where the HP30s’ response is weakest; while it looks as if the HP30s have a lot more bass and treble than the others, they’re actually fairly close to what I measured from the HP50s.
The HP30s’ waterfall plot shows less bass resonance than usual (not so surprising, considering there’s not much enclosure to resonate), and only a few extremely narrow and almost certainly inaudible resonances at a few higher frequencies.
The measured total harmonic distortion (THD) of the HP30s is a little on the high side in the bass, although I didn’t notice it in my listening tests. (I could, however, hear the distortion when I cranked up Mötley Crüe’s “Kickstart My Heart” to a level louder than I’d ordinarily listen.) The THD is about 2% at 100Hz, measured at the high listening level of 90dBA measured with pink noise. At the extremely high level of 100dBA, which I use only for measurement purposes, it hits 3% at 100Hz, rising to 11% at 20kHz.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the level of attenuation of outside sounds. The HP30s don’t offer much isolation, but few passive on-ear models do. There’s little or no attenuation below 600Hz, and attenuation of only 5 to 7dB from 600Hz to 2kHz. The HP30s wouldn’t be a good choice for air travel.
The HP30s’ impedance magnitude is fairly flat, running at or near the specified 32 ohms, except for a peak at 37 ohms right around 50Hz. The impedance phase is also mostly flat.
The sensitivity of the HP30s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified 32-ohm impedance, averages 109.2dB, which means they’ll play loud from any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the HiFiMan HE1000s 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 one that produced the most bass and the most characteristic response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the HE1000s’ frequency response, which is flat up to 1.5kHz, and rises sharply above that from 2 to 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 no audible effect on the HE1000s’ frequency response.
This chart compares the HE1000s (blue trace) with HiFiMan’s HE560s (red trace) and Audeze’s LCD-3s (green trace). The HE1000s have a similar response to the HE560s, with about 5dB more energy between 5 and 9kHz, and a little more bass to help balance out that treble peak. The LCD-3s have much less treble energy above 2.5kHz, and a flatter measured response, than either HiFiMan model. Note that, unlike with most speakers, a flat measured response in headphones does not necessarily equate with a flat perceived response.
The HE1000s’ waterfall plot may not look very clean at first glance, but if you look close you’ll see that all those little blue streaks are resonances of very narrow bandwidth about -40dB below the test signal. The only resonance shown here that might be audible is the combination of two adjacent -20dB resonances near 5kHz.
The total harmonic distortion (THD) of the HE1000s is well below audible levels, even at the extremely high level of 100dBA, measured with pink noise.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate attenuation of outside sounds. As is almost always the case with open-back headphones, the HiFiMan HE1000s provide essentially no noise isolation; any sounds from outside them will come right through.
The impedance magnitude of the HE1000s is nearly dead flat at 37 ohms; the impedance phase, too, is nearly flat.
The sensitivity of the HE1000s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified impedance of 35 ohms, is 88.1dB. Although that’s relatively low, as I say in the review, it was enough for me to get a fairly comfortable volume level from my smartphone.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the NightHawks 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 NightHawk earpiece around to several different locations on the ear/cheek simulator to find the position that gave the most bass and the best average of midrange and treble responses. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the NightHawks’ frequency response, which is most notable for being fairly flat, with little to none of the usual peak between 2 and 4kHz. There’s a dip centered at 1.2kHz, and a gradual bass rolloff.
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 audible effect on the NightHawks’ frequency response.
This chart compares the NightHawks (blue trace) with the Oppo Digital PM-3s (red trace) and the NAD Viso HP50s (green trace); both of the latter have received generally positive reviews. The NightHawks are clearly very different, with a more resonant (less flat) bass response and about 10dB less treble energy on average.
The NightHawks’ waterfall plot looks clean, with no major resonances, and very low resonance in the bass frequencies compared with most over-ear headphones I’ve measured.
The total harmonic distortion (THD) of the NightHawks is, as claimed by AQ, very low, even at the extremely high level of 100dBA, measured with pink noise. Even at 10Hz/100dB, there is only 1% THD. Note that because of the AQs’ semi-open-back design and the fact that I measure distortion in a very quiet room but not in an anechoic chamber, even the slight distortion seen in this chart may be mostly noise leaking in. (To improve the signal/noise ratio of this measurement, I use denim insulation on the back of open-back and semi-open-back headphones, but it’s not perfect.)
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The NightHawks’ isolation is roughly what I’ve measured from typical closed-back designs -- remarkable for a semi-open-back model. Consider AudioQuest’s claims for their diffuser confirmed.
The impedance magnitude of the NightHawks is basically flat, but my test gear measured it as 13 ohms -- much less than the specified 25 ohms. (I checked the test setup with a couple of other headphones; it was working properly.) The impedance phase, too, is basically flat.
The NightHawks’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal calculated for the claimed 25-ohm impedance, averages 100.4dB -- enough to get plenty of volume from almost any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the PSB M4U 4s 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 Comply foam eartips because that’s what designer Paul Barton used when voicing this model. For comparison, I also include a measurement taken with one of the supplied silicone eartips. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
Here is the frequency response of the M4U 4s using a supplied Comply foam eartip. It’s fairly similar to the responses we measure with most high-quality earphones, the only aspects of note being a little more energy than usual around 1.5kHz, and a little less than usual from 8 to 10kHz.
This chart shows the M4U 4s’ frequency response with the Comply foam eartip (red trace), and with the smallest of the supplied silicone tips (purple trace). The silicone tip causes a boost of 2-3dB in upper-midrange/lower-treble energy, a deep dip at 7kHz, and a 3-10dB increase in output between 8 and 12kHz. PSB’s silicone eartips will likely sound significantly brighter.
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 only a very slight effect on the M4U 4s, boosting the bass by 0.8dB at 20Hz (this will be inaudible), and reducing the output between 2 and 3kHz by 0.5-1dB (might be barely audible). Most balanced-armatures headphone show a much bigger and more significant frequency-response swing in this test.
You can see from this chart that the M4U 4s (blue trace) have more bass and treble output than do NAD’s Viso HP20 earphones (green trace), also designed by Paul Barton, or Sony’s XBA-H1s (red trace), a well-regarded hybrid design.
Other than the bass resonances seen in almost every spectral-decay measurement of headphones, the M4U 4s are essentially resonance-free.
The M4U 4s’ total harmonic distortion (THD) is very low, with just a couple of slight, narrow peaks at 1 and 4kHz, where the THD rises to 2.5-5% -- and that’s only at the extremely loud level of 100dBA, measured with pink noise.
In this chart, the sound-pressure level (SPL) of external noise is 75dB; the numbers below that indicate the degree of attenuation of external sounds. With either the Comply (green trace) or the silicone (purple trace) eartips, the M4U 4s’ isolation is outstanding for passive earphones. In fact, I had to expand this chart’s Y axis to accommodate the traces; normally, the lowest number along the Y axis is 30dB.
Here’s why, unlike with almost all other headphones using balanced-armature drivers, the M4U 4s’ response doesn’t really change when the user switches to a high-impedance source device. The impedances of most balanced-armature ’phones increase radically at high frequencies, but the M4U 4s’ impedance remains between 18 and 22 ohms throughout the audioband.
The M4U 4s’ sensitivity, measured from 300Hz to 3kHz with a 1mW signal calculated for the claimed 16-ohm impedance, is 99.7dB. Technically, that’s a little lower than average for earphones, but it’s plenty high enough to get a satisfying volume level from any portable device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
I measured the Bowers & Wilkins P5 Series 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 headphones around to several different locations on the ear/cheek simulator to find the spot that gave the most bass and the most characteristic response. As I usually do with on-ear headphones, I used the ear/cheek simulator’s clamping mechanism to ensure a good seal. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the P5 Series 2s’ frequency response. Its obvious distinguishing characteristic is the big dip in the midrange, centered at 500Hz. That peak, centered at 2.3kHz, is broad and high in amplitude, leading me to speculate that many listeners will find the P5s to sound a little bright. You may notice the disparity in bass response between the left (blue) and right (red) channels. That’s the best bass output I could get from the left channel after repeated repositionings of the earpiece, but keep in mind that the acoustical mating of the ear/cheek simulator to on-ear models is too fussy and unpredictable for me to take off points here.
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 little effect on the P5 Series 2s other than a boost in the bass of about 1dB below 80Hz.
This chart compares the P5 Series 2 with a well-regarded on-ear model, Beyerdynamic’s T51p (red trace), as well as my reference headphones for the $300 price point: NAD’s Viso HP50s (green trace). These are normalized to 94dB at 500Hz, per my standard practice for headphone frequency-response measurements and as mandated by the IEC’s 60268-7 standard, which makes it look as if the P5 Series 2s have a lot more bass and treble output than the other headphones -- but it’s more accurate to think of them as having a huge midrange dip around 500Hz.
The P5 Series 2s’ waterfall plot looks very clean, with no noteworthy resonances.
The total harmonic distortion (THD) of the P5 Series 2s is typical for on-ear ’phones. At the loud listening level of 90dBA (measured with pink noise), the THD rises to 2% at 20Hz, which you’re very unlikely to notice (unless you often listen to Saint-Saëns’s “Organ Symphony”). At the very loud listening level of 100dBA, the THD runs about 4.5% below 40Hz.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. With very little reduction of level in sounds below 1kHz, and none in the “jet engine band” of about 50-100Hz, this is typical performance for passive on-ear headphones.
The impedance of the P5 Series 2s is mostly flat, staying between 24 and 30 ohms through the entire audioband.
The sensitivity of the P5 Series 2s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 22 ohms impedance, is 101.2dB. This is typical for on-ear headphones.
. . . Brent Butterworth
brentb@soundstagenetwork.com
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