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Parent Category: Products

Category: Headphone Measurements

Created: 20 January 2018

Reviewed on: SoundStage! Solo, October 2018

I measured the Anandas using a G.R.A.S. Model 43AG ear/cheek simulator/RA0402 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 amp, with an Audio-gd NFB-1AMP used for distortion measurements. On the Model 43AG, I used the new KB5000 and KB5001 anthropomorphic simulated pinnae for most measurements, and the original KB0065 pinna for certain other measurements as noted. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The above chart shows the Anandas’ frequency response measured with the new KB5000 and KB5001 anthropomorphic simulated pinnae. This is a fairly typical response for large, open-back planar-magnetic headphones. While the response is flatter than I measure in most headphones, this doesn’t necessarily translate to a flat perceived response.

This chart shows the Anandas’ right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and the new KB5000 pinna, which I recently switched to because it more accurately reflects the structure and pliability of the human ear. This is just for sake of comparison with older measurements of mine.

Here you can see how the Anandas’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop or some cheap professional headphone amps. As with all the planar-magnetic headphones I can remember measuring, the output impedance of the source device has no audible effect on the tonal balance of the headphones.

This chart shows the Anandas’ right-channel response compared with two other high-end closed-back headphones (the Acoustic Research AR-H1s and Audeze LCD-Xes), as well as the Sony MDR-7506es, a standard fixture in audio production work that generally conform to the “Harman curve,” shown in research by Harman International to be the preferred over-ear headphone response for most listeners. These measurements use the older KB0065 pinna, because that’s the only measurement I have for the LCD-Xes. Clearly, the Anandas’ response is flatter than average, but in this measurement, that suggests that the sound may be somewhat midrange-focused.

The Anandas’ spectral decay (waterfall) chart shows the very-low-level midrange hash I often see with open-back planar-magnetic headphones, but after about 3 milliseconds, most of it’s down to -40dB, so I don’t see this as a problem -- especially since I generally like the sound of this headphone type. The bass resonance is nearly non-existent.

As usual with planar-magnetic headphones, the measured total harmonic distortion (THD) of the Anandas is almost non-existent even at very loud levels. Note that I’ve increased the resolution of this chart by reducing the range from 50% THD to 20%, which makes the Anandas’ distortion look higher relative to previous charts I’ve published. I initially chose 50% as my range many years ago, when I was measuring a lot of cheap, mass-market headphones, but few of the headphones I review now exceed 10% distortion.

In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The Anandas’ isolation is near zero, although for open-back headphones that may be a good thing, because it shows that the grille behind the driver offers very low acoustical impedance.

The Anandas’ impedance response is not quite as dead-flat as I’m used to seeing with open-back planar-magnetics; there are little bumps at 70 and 120Hz. However, these are far too small to affect the headphones’ performance. Electrical phase is almost perfectly flat.

Sensitivity of the Anandas, measured between 300Hz and 3kHz using a 1mW signal calculated for 25 ohms impedance, is 92.5dB. Although it should deliver a useable volume with most source devices, it won’t achieve natural dynamics and volume unless it’s used with a high-quality portable music player or an external amp.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 20 January 2018

Reviewed on: SoundStage! Solo, November 2018

I measured the AR-E010s using a G.R.A.S. Model 43AG ear/cheek simulator/RA0402 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 amp. On the Model 43AG, I used the new KB5000 and KB5001 anthropomorphic simulated pinnae for most measurements, and the stainless-steel coupler included with the RA0045 for certain other measurements as noted. For measurements in Bluetooth mode, I used a Sony HWS-BTA2W Bluetooth transmitter to get the signal to the earphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The above chart shows the AR-E010s’ frequency response measured with the new KB5000 and KB5001 anthropomorphic simulated pinnae. This is within the bounds of what I typically measure with good-sounding earphones, with just a little more bass and treble output than average.

This chart compared the response of the AR-E010s using the unbalanced analog audio cable with the response using the Bluetooth cable (which of course employs the cable’s internal amplifiers). The only significant difference seems to be a little less bass response in Bluetooth mode. While this could be due to the signal gating I had to use to counteract Bluetooth’s latency, the result was consistent no matter how I set the gate, so I think it’s inherent to the Bluetooth cable -- and it’s probably why the bass with the Bluetooth cable sounded a little better-defined to me.

This chart shows the AR-E010s’ right-channel frequency response measured with the RA0045 ear simulator’s stainless-steel coupler (which I’ve used for years) and the new KB5000 simulated pinna, which I recently switched to because it more accurately reflects the structure and pliability of the human ear and provides a more realistic simulacrum of what you’ll actually experience with headphones or earphones. This is just for sake of comparison with older measurements of mine.

Here you can see how the AR-E010s’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop or some cheap professional headphone amps. For hybrid earphones, this is an extremely impressive result -- the sound barely changes with the source impedance. Most earphones using balanced armatures show a big difference on this test.

This chart shows the AR-E010s’ right-channel response compared with a few other midpriced earphones: the Sennheiser HD 1 Free Bluetooth earphones, the 1More Quad Drivers, and the AKG N5005s, the earphones that currently best conform to the “Harman curve,” shown in research by Harman International to be the preferred in-ear headphone response for most listeners. The AR-E010s do seem to have a couple dB of extra treble and bass. I suspect that the little extra oomph in the bass centered at 45Hz is what made us think the midbass sounded a bit muted.

The AR-E010s’ spectral decay (waterfall) chart shows significant resonance only at about 3.6kHz, which corresponds with the earphones’ response peak, but it lasts only about 3ms.

While the AR-E010s do show some distortion at the extremely loud listening level of 100dBA, they show no audible distortion at the merely very loud level of 90dBA. This was measured with a wired connection; the internal amps of the Bluetooth cable may add some distortion, but my analyzer can’t compensate for Bluetooth’s latency when doing distortion measurements.

In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The AR-E010s’ isolation is better than average for non-noise-canceling earphones, although not as good as I measured from the Massdrop x NuForce EDC3 earphones, which have smaller earpieces that fit more snugly into the ears.

The AR-E010s’ impedance response is essentially flat at 26 ohms, with just a little wiggle above 6kHz. This is extremely impressive for a hybrid earphone; most earphones with balanced armatures show large impedance swings in the treble.

Sensitivity of the AR-E010s, measured between 300Hz and 3kHz using a 1mW signal calculated for 26 ohms impedance (my impedance measurement -- the rated impedance is not listed on the website or in the manual), is 110.4dB, adequate to achieve very loud volumes from any source device.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 20 January 2018

Reviewed on: SoundStage! Solo, November 2018

I measured the TH909s using a G.R.A.S. Model 43AG ear/cheek simulator/RA0402 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 amp, with an Audio-gd NFB-1AMP used for distortion measurements. On the Model 43AG, I used the new KB5000 anthropomorphic simulated pinna for most measurements, and the original KB0065 pinna for certain other measurements as noted. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The above chart shows the TH909s’ frequency response measured with the new KB5000 and KB5001 anthropomorphic simulated pinnae. This is a fairly typical measurement for headphones in general, although most audiophile-oriented headphones are more or less flat up to about 2kHz. The TH909 has relatively more bass and less midrange.

This chart shows the TH909s’ right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna, which I recently switched to because it more accurately reflects the structure and pliability of the human ear. This is just for sake of comparison with older measurements of mine.

This chart shows how the TH909s’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop or some cheap professional headphone amps. There’s just a slight bass boost with the high-impedance (75-ohm) source.

This chart shows the TH909s’ right-channel response compared with two other high-end open-back headphones (the Audeze LCD-Xes and the Sennheiser HD 800 Ses), as well as the Sony MDR-7506es, a standard fixture in audio production work that generally conforms to the “Harman curve,” shown in research by Harman International to be the preferred over-ear headphone response for most listeners. These measurements use the older KB0065 pinna, because that’s the only measurement I have for the HD 800 Ses. You can see that the TH909s have substantially more bass and a little less midrange energy than the competitors shown here.

The TH909s’ spectral decay (waterfall) chart shows no resonances worth commenting on.

Measured total harmonic distortion (THD) of the TH909s is trivial. Even at the extremely loud level of 100dBA, it’s only 2% at 20Hz.

In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The TH909s’ isolation is above average for an open-back model, although it’s still much less than what you get from closed-back headphones such as the NAD Viso HP50s (also shown).

The TH909s’ impedance response is fairly typical for high-end dynamic-driver headphones, with a fairly flat response except for a resonant peak in the bass, at 36Hz. It’s pretty much in accord with Fostex’s rating of 25 ohms. The phase is also generally flat.

Sensitivity of the TH909s, measured between 300Hz and 3kHz using a 1mW signal calculated for 25 ohms impedance, is 100.4dB. That’s pretty high for audiophile-oriented headphones, and it means that the TH909s can be reasonably well driven from a smartphone or laptop computer.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 January 2018

I measured the AKG N60 NC Wireless 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 a Musical Fidelity V-CAN amp. On the Model 43AG, I used the original KB0065 simulated pinna for most measurements as well as the new KB5000 pinna for certain measurements, as noted. For Bluetooth-sourced measurements, I used a Sony HWS-BTA2W Bluetooth transmitter to send signals from the Clio 10 FW to the headphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The N60 NCs’ frequency response (taken with a Bluetooth signal with NC on) looks very by the book, with a rise in bass response at about 100Hz, a strong peak at 3kHz, and a weaker peak between 6 and 7kHz. The level of bass relative to the midrange and treble may be affected to some degree by the gating required for the analyzer to compensate for Bluetooth’s latency; the actual level may be a couple dB higher.

This chart shows the right-channel frequency response of the N60 NC Wireless measured with Bluetooth and NC on, and in wired mode with NC on and off. The difference in response between the Bluetooth and wired modes is negligible (and may be due entirely to response differences caused by the gating used for the Bluetooth measurement). The big difference is when NC is switched on and off: with no NC, the bass response is greatly reduced and the headphones are likely to sound thin. Although I don’t show it in this chart, I also measured the response of a wired connection, adding 70 ohms output impedance to the V-CAN amp’s 5-ohm native output impedance, but saw no notable change in response.

In this chart, the N60 NC Wireless is compared with the response of the original wired version, the N60 NC. It appears that the two headphones were voiced according to somewhat different philosophies.

This chart shows the N60 NCs’ right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna. (I’ll be switching permanently to the new pinna because it more accurately reflects the structure and pliability of the human ear. I include this chart mostly for future reference rather than as something you should draw conclusions from; I intend to show both measurements in every review for at least the next year before I start using only the new pinna.)

This chart shows the N60 NCs’ right-channel frequency response compared with the FRs of three other NC headphone models: the Bose QC35, the PSB M4U 2 (generally considered to rank among the best-sounding NC headphones), and the Sennheiser HD 4.50 BTNC. Except for the AKG’s reduced bass response (possibly due to its on-ear design; the other models are over-ear), its response is within the norm for headphones of this type.

The N60 NCs’ spectral-decay (waterfall) chart shows just a single, very narrow, low-magnitude (-40dB) resonance at 3kHz; this corresponds with the headphones’ lower-treble response peak and won’t be problematic.

The N60 NCs’ total harmonic distortion (THD), measured with a wired connection because the Clio 10 FW’s sine sweeps can’t accommodate Bluetooth’s latency, is effectively unmeasurable, swamped by the measurement’s inherent noise. This is outstanding performance, especially for relatively small on-ear headphones.

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but an 85dB level lets me get better measurements of NC headphones, which demand a lower noise floor.) The isolation of the N60 NCs is basically about average for NC headphones, but a little above average for an on-ear model -- better than the original N60 NC (which has much smaller earpads), with about a 15dB attenuation right where airplane cabin noise is usually worst: 100-200Hz.

The N60 NCs’ impedance magnitude is very high, which is common for active headphones, and measures the same whether the headphones are powered on or off. I expect that all the high impedance in the bass is the reason for the weak bass response in passive wired mode. The phase shifts from 0° at 20Hz to -72° at 20kHz, which doesn’t matter when the headphone is in active mode.

The N60 NCs’ sensitivity in wired mode, measured between 300Hz and 3kHz with a 1mW signal calculated for 32 ohms impedance, is 104.1dB -- they’ll easily play very loud when you plug them into an airplane seat’s headphone jack.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 January 2018

I measured the Acoustic Research AR-H1s 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 amp. On the Model 43AG, I used the original KB0065 simulated pinna for most measurements as well as the new KB5000 pinna for certain measurements, as noted. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The AR-H1s’ frequency response runs close to the norm for open-back planar-magnetic headphones, with a couple of exceptions. First, the response is flatter than normal, with a less prominent peak in the 2.5-3kHz range than I’m used to seeing. Second, the response in the midrange is slightly jagged, with a peak/dip in the region between 600 and 700Hz and another between 1.6 and 2kHz. However, these sorts of low-magnitude, high-Q anomalies typically aren’t very audible, if at all.

This chart shows the AR-H1s’ measured right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna, which I’ll be switching to because it more accurately reflects the structure and pliability of the human ear. I include this mostly for future reference rather than as something you should draw conclusions from; I intend to show both measurements in every review for at least the next year before I begin using only the new pinna.

This chart shows the results of adding 70 ohms output impedance to the V-CAN’s 5-ohm output impedance, to simulate the effects of using a typical low-quality headphone amp. The difference is practically zero, with an inaudible bass boost (about 1dB at 10Hz) visible with the higher output impedance.

This chart shows the AR-H1s’ measured right-channel frequency response compared with those of the similar Oppo Digital PM-2s, the HiFiMan HE400i’s (a well-regarded but less costly planar-magnetic headphone), and the Beyerdynamic Amiron Homes (dynamic-driver, open-back headphones). As you can see, the AR-H1s’ response is the flattest, though it’s very similar to that of the PM-2s. The other headphones have stronger treble response above 4kHz.

The spectral decay (waterfall) chart shows a lot of resonance, even for a planar-magnetic headphone, with very strong but narrow resonances between 600 and 700Hz and between 1.6 and 2kHz -- which correspond precisely with the peak/dip series I noted in the frequency response.

The AR-H1s’ total harmonic distortion (THD) is practically nonexistent even at extremely loud listening levels, as is common with large planar-magnetic models.

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but an 85dB level lets me get better measurements of noise-canceling headphones, which demand a lower noise floor.) As expected, the AR-H1s offer negligible isolation -- even less than the Oppo Digital PM-2s, and far less than sealed and noise-canceling models.

The AR-H1s’ impedance magnitude and phase are extremely flat, with the impedance at almost precisely 31 ohms throughout the audioband, and negligible phase shift.

The sensitivity of the AR-H1s, measured between 300Hz and 3kHz with a 1mW signal at the rated 33 ohms impedance, is 96.5dB. That’s a little on the low side; to get the best results with the AR-H1s, you’ll want to use a headphone amp, a good portable player, or an Apple iOS device.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 December 2017

I measured the WH-1000XM2s 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 amp. On the Model 43AG I used the original KB0065 simulated pinna for most measurements, as well as the new KB5000 pinna for some measurements, as noted. For Bluetooth-sourced measurements I used a Sony HWS-BTA2W Bluetooth transmitter to send signals from the Clio 10 FW to the headphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was applied.

The WH-1000XM2s’ frequency response (shown here with a Bluetooth signal with NC on and with a cabled connection and power off) looks fairly standard, with the usual peak in the 2.5kHz range and another in the 6-8kHz range. What’s unusual is that, despite my best attempts, I got a little more left/right variance than I usually do. Also, it’s obvious that Sony didn’t put a ton of work into getting these headphones to sound good in passive mode. Although I don’t show it here, switching from a 5- to a 75-ohm source in cabled/power-off mode produced a boost of typically 4dB in the bass (depending on frequency), which means that these headphones will take on a different tone if the battery runs down and you plug them into a cheap PC laptop -- admittedly, probably a very minor concern.

This chart shows the WH-1000XM2s’ measured right-channel frequency response in Bluetooth mode with NC on, measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna. (I’ll eventually switch to the new pinna, because it more accurately reflects the structure and pliability of the human ear, and include it here mostly for future reference rather than as something you should draw conclusions from. I intend to show both measurements in every review for at least the next year before I begin using only the new pinna.)

This chart, measured with pink noise and Clio’s FFT real-time analyzer function (necessary to capture an accurate comparison of the WH-1000XM2s’ various modes, as the Bluetooth mode introduces a latency of about 200ms), shows that the WH-1000XM2 can sound quite different depending on which mode it’s set to. Incidentally, Ambient mode, which lets in outside sounds, measures effectively the same as NC Off mode, whether the headphone is cabled or connected through Bluetooth.

This chart shows the WH-1000XM2s’ measured right-channel frequency response compared with those of three other NC headphones: the Bose QC35 (original model), the PSB M4U 2 (generally considered among the best-sounding NC headphones), and the Sennheiser HD 4.50 BTNC. The WH-1000XM2 seems pretty much in the ballpark when it comes to responses typical of NC headphones -- or headphones in general, for that matter.

The spectral decay (waterfall) chart, measured with the WH-1000XM2s in Bluetooth/NC mode, shows a spectrum of plentiful but narrow resonances between 1 and 6kHz -- a strange result for dynamic headphones, but something I often see even in the best planar-magnetic models. It doesn’t concern me.

The total harmonic distortion (THD) of the WH-1000XM2s, measured with a wired connection because the Clio 10 FW’s sine sweeps can’t accommodate Bluetooth’s latency, is somewhat on the high side in passive cabled mode, but there are unusually large peaks in distortion at 70Hz and 2kHz when NC is switched on and the level rises to the extremely high 100dBA standard I use (and which most headphones pass pretty easily). I didn’t notice the distortion when I was listening, and considering that it’s limited to two narrow bands, you probably wouldn’t, either. I speculate that DSP-based EQ inside the headphones is pushing the internal amp past its limits.

In this chart the level of external noise is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but an 85dB level lets me get better measurements of NC headphones, which demand a lower noise floor.) The isolation of the WH-1000XM2s is pretty good for active NC headphones; they can’t beat the industry-leading Bose, but they easily beat the AKG and Sennheiser models I compare them with here.

The WH-1000XM2s’ impedance magnitude is dead flat in powered mode with a cabled connection. With power off, there’s an impedance swing in the bass from the specified 14 ohms up to 39 ohms, as well as some phase shift in the bass, which is why in passive cabled mode you’ll be able to hear a difference in bass response if you plug the Sonys into a low-quality headphone amp such as the ones built into typical laptop PCs.

The sensitivity of the WH-1000XM2s in wired mode with power off, measured between 300Hz and 3kHz with a 1mW signal and calculated for the specified 14 ohms impedance, was 96.3dB. Wired with power on, it’s 101.7dB for the specified 46-ohm impedance in that mode. This means that the WH-1000XM2s won’t play very loud if the batteries run down, but will work just fine if you’re on an airplane with NC on and are using a cabled connection to the airplane’s in-seat entertainment system.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 December 2017

I measured the Monolith M300s 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 amp. With the G.R.A.S. I used the original KB0065 simulated pinna for most measurements, as well as the new KB5000 pinna for certain measurements, as noted. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The M300s’ frequency response is quite unusual, even for such an unusual set of earphones. Basically, if you moved the whole curve 1kHz higher, it would look reasonably normal. Most earphones and headphones have a big response peak between 2 and 3kHz, but the M300s’ peak is centered at 1.2kHz. The deep dip at 1kHz represents a cancellation, I would guess due to the internal acoustics of the eartube, but considering that it’s a dip, and a very narrow one, I doubt it would be readily audible.

This chart shows the M300s’ right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna, which more accurately reflects the structure and pliability of the human ear. I plan to show both measurements in every review for at least the next year before I begin to use only the new pinna, and include this measurement here mostly for future reference rather than as something you should draw conclusions from. Because of the KB5000’s more realistic construction, I’d consider the measurements taken with it more representative of the Monolith M300s’ performance, but unfortunately, at the moment I have only the right-ear model of the new pinna.

This chart shows the results of adding 70 ohms output impedance to the V-CAN’s 5-ohm output impedance to simulate the effects of using a typical low-quality headphone amp. The difference is zero; those little squiggles in the bass are due to noise caused by the much lower recorded level of the signal with the higher-impedance output. (I scaled up the 75-ohm result by 10.3dB in the chart for comparison purposes.)

This chart shows the M300s’ right-channel frequency response compared with that of the very similar Audeze iSine10s, the well-regarded PSB M4U 4 hybrid dynamic/balanced-armature earphones, and the Focal Sphears (rather “normal” single-driver dynamic earphones). The PSBs and Focals have the broad bass hump and strong upper-mid/lower-treble peaks typical of most earphones; the Audezes’ response looks much like that of a typical over-ear planar-magnetic model; but the M300s occupy a world of their own.

The spectral-decay (waterfall) chart looks unusual: While the resonances are well damped and die out quickly, they’re higher in magnitude than the norm, with an especially strong resonance centered at 1kHz.

The M300s’ total harmonic distortion (THD) is effectively nonexistent, even at loud listening levels, with just a narrow blip of distortion centered at 1kHz -- the same frequency as the dip in the frequency response, and the strongest resonance in the spectral-decay measurement. In a rather extraordinary display, the measured distortion at 100dBA is no higher than at 90dBA -- there’s actually an orange trace representing the distortion at 100dBA, but it’s completely obscured by the green trace at 90dBA.

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched from measuring at a level of 75dB to a level of 85dB. This doesn’t change the way the isolation curves look, but 85dB lets me get better measurements of noise-canceling headphones, which demand a lower noise floor.) Like the Audeze iSine10s, the M300s offer very little isolation from outside sounds; voices and other sounds will leak right in. However, the M300s do offer a little more isolation than typical over-ear, open-back, planar-magnetic headphones, such as the Monoprice M1060s included in this chart.

The M300s’ impedance magnitude and phase are about as flat as they could be, respectively at 26 ohms and a maximum phase shift of about +6° at 20kHz.

The sensitivity of the Monolith M300s, measured between 300Hz and 3kHz with a 1mW signal at the M300s’ specified impedance of 22 ohms, is 109.5dB. That’s high -- any conceivable source device should be able to drive the M300s to very loud levels.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 October 2017

I measured the HD 4.50 BTNCs 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 amp. I used the Model 43AG’s original KB0065 simulated pinna for most measurements, as well as the new KB5000 pinna for certain measurements, as noted. For Bluetooth-sourced measurements, I used a Sony HWS-BTA2W Bluetooth transmitter to send signals from the Clio 10 FW to the headphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

The HD 4.50 BTNCs’ frequency response, taken with a Bluetooth signal with noise canceling (NC) on, may look a little weird due to its two prominent peaks centered at roughly 50Hz and 2.2kHz. Actually, it’s not far from what’s considered a standard “flat” headphone response: a broad bass peak, a midrange dip, a prominent response peak around 2.5kHz, and a lesser peak around 6kHz.

This chart shows the HD 4.50 BTNCs’ measured right-channel frequency response measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna, which I’ll be switching to because it more accurately reflects the structure and pliability of the human ear. I include this mostly for future reference rather than as something you should draw conclusions from; I intend to show both measurements in every review for at least the next year before I begin to use only the new pinna.

This chart shows the right-channel frequency response of the HD 4.50 BTNCs measured with Bluetooth and NC on, with Bluetooth on and NC off, and with a wired connection. Obviously, switching NC off substantially changes the sound of these headphones. Although I don’t show it in the chart here, I also measured the response of a wired connection, adding 70 ohms output impedance to the V-CAN amp’s 5-ohm native output impedance, but saw no notable change in response.

This chart shows the HD 4.50 BTNCs’ measured right-channel frequency response compared with those of three other NC headphones: the AKG N60 NC Wireless, the Bose QuietComfort 35, and the PSB M4U 2 (the last generally considered to rank among the best-sounding NC headphones). The HD 4.50 BTNCs’ response is similar to that of the AKG.

The spectral-decay (waterfall) chart shows a few very narrow, low-magnitude resonances between 1.5 and 2.1kHz; these are not likely to be audible.

The total harmonic distortion (THD) of the HD 4.50 BTNCs, measured with a wired connection because the Clio 10 FW’s sine sweeps can’t accommodate Bluetooth’s latency, is negligible at 90dBA. At 100dBA, it’s about average for dynamic over-ear headphones; it rises to 3% at 60Hz, and spikes from 3% at 30Hz to 13% at 20Hz -- but note that 100dBA is an extremely loud listening level, and that few music recordings have significant content below 30Hz.

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but a level of 85dB allows me to get better measurements of NC headphones, which demand a lower noise floor.) In this measurement, the isolation of the HD 4.50 BTNCs looks somewhat below average for NC headphones, which surprises me because my subjective tests showed it to be better, and this measurement usually corresponds closely with subjective impressions.

The HD 4.50 BTNCs’ impedance magnitude and phase in wired mode are nearly flat, averaging about 23 ohms and with negligible phase shift.

The sensitivity of the HD 4.50 BTNCs in wired mode, measured between 300Hz and 3kHz with a 1mW signal and calculated for the specified 18 ohms impedance, is 100.9dB. This means that if you have to use a wired connection, the Sennheisers will still play plenty loud.

. . . Brent Butterworth
brentb@soundstagenetwork.com