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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

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Parent Category: Products

Category: Headphone Measurements

Created: 15 March 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 01 March 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 01 March 2016

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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Parent Category: Products

Category: Headphone Measurements

Created: 15 February 2016

I measured the Edition Xes 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 tried the headphone at several different positions 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 Edition Xes’ frequency response, which is flat up to 1.5kHz. The strong peak at 3kHz is found with most headphones, and is thought to make them sound more like conventional speakers in a room, but this peak is stronger than we usually see. The bass is a little rolled-off compared with some other open-back planar-magnetic headphones.

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 boosts the Edition Xes’ bass below 80Hz by about 1dB -- a subtle difference.

This chart compares the Edition Xes with three other open-back planar-magnetic models: HiFiMan HE1000, Audeze LCD-3, and Oppo Digital PM-1. Compared with the HE1000s, the Edition Xes have less bass but also less treble above 3kHz, so the two might have a similar perceived tonal balance. But there’s no denying that the Edition Xes’ 3kHz peak is stronger than average.

Like the HE1000s’, the Edition Xes’ waterfall plot doesn’t look clean at first glance, but all those resonances in the high frequencies are extremely narrow and well spread out. There’s almost no resonance in the bass, which is unusual for headphones, even open-back models. I speculate that the only resonance seen here that might be readily audible is the one centered at 1kHz.

The total harmonic distortion (THD) of the Edition Xes is insignificant even at levels far too loud to listen to safely.

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. Like all open-back headphones, including the HiFiMan HE560s and Audeze LCD-Xes shown here, the Edition Xes offer essentially no isolation from outside sounds. I included the isolation measurement of the Oppo PM-3s to illustrate the difference between open- and closed-back models in this regard.

The impedance magnitude of the Edition Xes is almost perfectly flat at 21 ohms; the impedance phase is about as flat as it gets.

The sensitivity of the Edition Xes, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 25 ohms impedance, is 96.5dB. That’s below average for headphones in general, and much less than the specified 103dB (HiFiMan doesn’t specify the conditions for that measurement), but it should be adequate to get a fairly comfortable listening volume from a smartphone.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 February 2016

I measured the Everest Elite 700s 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 with the most bass and the most characteristic response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed. However, I did run a TruNote auto-EQ sweep (see review for details) to optimize the response of the Everest 700s for the ear/cheek simulator. For all measurements, I used a cabled connection; adding a Bluetooth transmitter introduces latency and thus requires gating, which introduces anomalies into the measuring.

This chart shows the Everest Elite 700s’ frequency response with noise canceling (NC) on. The results are fairly typical, although with a somewhat stronger peak at 3kHz than I’m used to seeing. (This may be an anomaly caused by TruNote’s attempt to calibrate itself for the G.R.A.S. 43AG’s metal cheek plate, fake rubber ear, and unnaturally round simulated ear canal.) The match between the left and right channels is the best I could achieve. I can’t be sure if this is the result of minor differences in the fit of the two earpieces on the ear/cheek simulator, or if the internal acoustics of the two earpieces are different (a phenomenon I’ve seen before in NC headphones, caused by the varying amounts of space occupied by the internal electronics).

This chart shows the frequency response of the Everest Elite 700s with NC on and with the headphones powered completely off. Obviously, the tonal balance is very different in the two modes; the JBLs have very little bass in passive mode, so best not to let the battery run down.

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 effect in NC mode. In passive mode, the balance will get subtly more trebly with higher-impedance sources.

This chart compares the Everest Elite 700s with three other noise-canceling headphones -- the Bose QC25s, the Definitive Technology Symphony 1s, and the PSB M4U 2s -- all with NC on. The main difference between the JBLs and the others is the larger peak at 3kHz. Most headphones have such a peak somewhere in that octave of audio, but how big the peak should be remains a matter of debate (and, as noted above, it’s possible the peak is the result of the TruNote auto EQ slightly miscalibrating itself for the nonhuman characteristics of the test gear). The Everest Elite 700s also have less deep bass than the others, but considering that music seldom has much content below 30Hz, you probably wouldn’t notice that.

The Everest Elite 700s’ waterfall plot (shown here with NC on) is exceptionally clean in the bass, with much less resonance than I see with most headphones. There are a few ultra-high-Q resonances -- at about 6, 8, 12, and 16kHz -- but considering that they’re so narrow, so low in level (-40dB), and so high in frequency, I’d be surprised if anyone can hear them.

The total harmonic distortion (THD) of the Everest Elite 700s, shown here with NC on, is insignificant at the loud level of 90dBA, but the extremely loud level of 100dBA (which I include more for testing purposes than for any sort of real-world evaluation) pushes the internal amp or the driver over the limit, resulting in considerable distortion below 2kHz. But, as I always say, if you listen long at this volume, you won’t be hearing much of anything after a while.

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. I recently did some acoustical measurements of the cabins of jet airliners in flight, and found that most of the noise is between 100 and 1200Hz. In this band, the Everest Elite 700s are roughly the equal of the PSB M4U 2s -- but, as usual, both are handily beat by the Bose QC25s.

As often occurs with active headphones, the impedance of the Everest Elite 700s was greater than 1000 ohms in NC mode and thus immeasurable on my Clio analyzer. In passive mode the impedance is largely flat, averaging about 24 ohms and presenting an essentially flat phase response.

The sensitivity of the Everest Elite 700s, measured between 300Hz and 3kHz with a 1mW signal calculated for 32 ohms impedance (my default when measuring active headphones), is 97.2dB in passive mode and 103.6dB in active mode (NC on). Thus, the JBL Everest Elite 700s, unlike many noise-canceling headphones, still produce a decent amount of volume when their internal battery runs down.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 January 2016

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

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Parent Category: Products

Category: Headphone Measurements

Created: 15 December 2015

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