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Parent Category: Products

Category: Headphone Measurements

Created: 15 October 2016

I measured the Sonorous IIIs 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 distortion measurements. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

The Sonorous IIIs’ frequency response is flatter than I’m used to seeing from headphones of this type. Instead of the usual response peak around 3kHz, which is generally thought to make headphones sound more like speakers in an actual room, there’s a broad, shallow peak between 1.5 and 6kHz. I can’t recall seeing a measurement like this before, so I hesitate to speculate as to what effect it might have on the sound. I wonder if the lack of a 3kHz peak is why the Sonorous IIIs sounded a bit less spacious than some competing models.

Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amplifier, has no significant effect on the Sonorous IIIs’ tonal balance.

This chart shows the Sonorous IIIs’ response compared with two well-regarded, midpriced closed-back models: the NAD Viso HP50s ($299) and the Oppo Digital PM-3s ($399). It’s easy to see that the Sonorous IIIs are something different, with less treble response than either competitor. But that’s not necessarily a bad thing -- the Sonorous IIIs’ somewhat rolled-off bass could counteract it, to give the headphones a perceived flat response.

Their spectral-decay (waterfall) plot indicates that the Sonorous IIIs seem to have a bit stronger initial resonance below 700Hz than I’m used to seeing, but it’s well damped, and drops to very low levels (-40dB and below) within 5 milliseconds.

The total harmonic distortion (THD) of the Sonorous IIIs is very low. Even at the extremely loud level of 100dBA, it rises to just 3% at 20Hz.

In this chart, the level of external noise is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. For reference, I’ve included another set of passive closed-back headphones, the NAD Viso HP50s, as well as that of a set of headphones with active noise canceling: the Bose QC25s ($299). The Sonorous IIIs’ isolation is not quite as good as the Viso HP50s’, probably because the Finals’ large earpads made it tough to get a good seal on the ear/cheek simulator (and on my actual, unsimulated ear and cheek). As always with this measurement, your results may vary; the better the fit, the better the isolation.

The Sonorous IIIs’ impedance is essentially flat, averaging 19 ohms, with negligible phase shift.

The sensitivity of the Sonorous IIIs, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified impedance of 16 ohms, is 105.8dB. That’s excellent for headphones of this type; there should be no problem getting loud volumes from any source device.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 September 2016

I measured the Audeze Sines 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 G.R.A.S.’s clamping mechanism to ensure a good seal of the earpad against the simulator’s fake rubber ear. For all but one measurement, I used the standard analog cable. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

The Sines’ frequency response is typical of planar-magnetic headphones, except that there’s more bass rolloff than I usually see. There’s also not a lot of energy in the upper treble, above about 6kHz. I was occasionally able to measure more bass than you see here, depending on how I positioned the headphones on the ear/cheek simulator, but this chart represents the result I got about 90% of the time.

Because my test equipment doesn’t have an Apple Lightning output, and I have no device that will convert the Clio’s S/PDIF output to Lightning, I had to compare the Sines’ performance from the digital and analog inputs using a relatively crude technique: playing pink noise from my iPod Touch through the Sines using both cables, and comparing the results using TrueRTA with 1/12th-octave smoothing. Still, my method clearly shows that the sounds via the two cables are substantially different. Using the digital cable results in considerably more bass output: +3.9dB at 50Hz. Considering that the Sines’ bass with the analog input was unaffected by changes in source impedance, my guess is that this difference reflects an intentional engineering choice to boost the bass with the digital cable.

Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp shows that the Sines will be somewhat sensitive to source-device impedance when used with the analog cable. With the higher-impedance source, the lower-treble response is boosted by 2.8dB at 2.6kHz.

This chart shows that the Sines have a more midrange-focused sound than two other midpriced closed-back models, NAD’s Viso HP50 and Oppo Digital’s PM-3; both of these have stronger bass and upper-treble responses.

The Sines’ spectral decay (waterfall) plot shows a broad area of resonance between 1.5 and 6kHz, but these resonances drop quickly in level, and are gone within 5ms.

The total harmonic distortion (THD) of the Sines is pretty close to zip, even at extremely high listening levels.

In this chart, the level of external noise is 75dB; the numbers below that indicate the degree of attenuation of outside sounds. The Sines have about the same amount of isolation as another midpriced, closed-back headphone model, NAD’s Viso HP50.

The Sines’ impedance is flat at about 22 ohms, except for a 40-ohm peak centered at 2.5kHz. The phase response is almost entirely flat, except for a mild wrinkle that corresponds with the impedance peak.

The sensitivity of the Sines, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 20 ohms impedance, is 96.6dB -- a little low. This is enough to produce decent volume from a smartphone or tablet, but if you like to crank the sound up loud, use the digital cable or a separate headphone amp.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 September 2016

I measured the HD 630VBs 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 earlobe. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed. Except as noted, measurements were made with the Variable Bass (VB) control in the middle setting.

The HD 630VBs, measured here with the VB dial set to its midpoint, have an idiosyncratic frequency response. Obviously, there’s a large dip between 150 and 600Hz. The peak in the 2-3kHz range, a prominent feature of most headphones’ measured response, is unusually broad, spanning the range from about 1.5 to 4kHz, and there’s a strong peak centered at 8kHz. This is the best match I was able to achieve between the left and right channels; it’s possible the inclusion of the VB control on the right earpiece has some effect on the acoustics of that earpiece.

This chart shows how the VB control affects the HD 630VBs’ response. The control’s operation is not linear; the magnitude and bandwidth of its effect are much greater between the middle and Max positions than between the middle and Min positions. Sennheiser specifies the control’s range as +/-5dB at 50Hz, which is accurate. At 20Hz, the adjustment range is +/-8.8dB. The control has no significant effect above about 800Hz.

Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp suggests that the design of the source device will have considerable effect on the HD 630VBs’ sound. The response, measured with the VB control in the middle setting, is considerably different with the two source impedances. Unsurprisingly, however, the difference is in the range where the VB control is effective; when users adjust the bass control to their taste, they will likely dial out any effect of the source impedance on the headphones’ response.

This chart shows that the HD 630VBs’ voicing is considerably different from that of two well-regarded, closed-back, over-ear models, NAD’s Viso HP50 and Sennheiser’s own Momentum. The HD 630VBs’ output is much lower between 150 and 400Hz, and significantly greater between 3 and 5kHz.

The HD 630VBs’ spectral decay (waterfall) plot shows three prominent resonances, all at a very high Q and a low level of about -40dB; I suspect that these are inaudible. There is a low-Q resonance band between 2 and 4kHz, but the resonance is at only -20dB, and dies out in less than 4ms; this resonance is a result of a peak in the headphones’ response, so it can be considered a part of the HD 630VBs’ sound rather than an audible flaw. The resonance below 1kHz is visible in this measurement with almost every headphone I test; the HD 630VBs’ resonance is lower than average.

The total harmonic distortion (THD) of the HD 630VBs is low, maxing out at 2% even at the extremely high output level of 100dBA. This measurement was taken with the VB control at its midpoint setting.

In this chart, the external noise level is 75dB SPL; numbers below that indicate the degree of attenuation of outside sounds. The HD 630VBs are a little above average for passive closed-back headphones, with 6-10dB of additional noise reduction between 200 and 400Hz compared to the NAD Viso HP50s, closed-back headphones with isolation measurements that are typical for their type. This is especially useful because it’s within the “jet-engine band,” the most prominent noise in a typical airliner cabin.

With the VB control at its middle position, the HD 630VBs’ impedance runs from 100 ohms in the bass to 24 ohms in the midrange. The phase shift is modest, maxing out at +32 degrees at 20kHz.

The VB control has a large effect on the HD 630VBs’ impedance at low frequencies. With the control set to Min, the impedance measures 242 ohms at 20Hz; at Max, it’s 30 ohms at 20Hz; and at the midpoint setting it’s 100 ohms.

The sensitivity of the HD 630VBs, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 23 ohms impedance, is 100.6dB. This means that a smartphone or tablet should be able to drive the HD 630VBs to adequate volume levels.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 August 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 01 July 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 01 June 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 01 April 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 15 March 2016

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