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Parent Category: Products

Category: Headphone Measurements

Created: 01 August 2015

I measured the Bowers & Wilkins P5 Series 2s using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-Can headphone amplifier. I moved the headphones around to several different locations on the ear/cheek simulator to find the spot that gave the most bass and the most characteristic response. As I usually do with on-ear headphones, I used the ear/cheek simulator’s clamping mechanism to ensure a good seal. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

This chart shows the P5 Series 2s’ frequency response. Its obvious distinguishing characteristic is the big dip in the midrange, centered at 500Hz. That peak, centered at 2.3kHz, is broad and high in amplitude, leading me to speculate that many listeners will find the P5s to sound a little bright. You may notice the disparity in bass response between the left (blue) and right (red) channels. That’s the best bass output I could get from the left channel after repeated repositionings of the earpiece, but keep in mind that the acoustical mating of the ear/cheek simulator to on-ear models is too fussy and unpredictable for me to take off points here.

Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp has little effect on the P5 Series 2s other than a boost in the bass of about 1dB below 80Hz.

This chart compares the P5 Series 2 with a well-regarded on-ear model, Beyerdynamic’s T51p (red trace), as well as my reference headphones for the $300 price point: NAD’s Viso HP50s (green trace). These are normalized to 94dB at 500Hz, per my standard practice for headphone frequency-response measurements and as mandated by the IEC’s 60268-7 standard, which makes it look as if the P5 Series 2s have a lot more bass and treble output than the other headphones -- but it’s more accurate to think of them as having a huge midrange dip around 500Hz.

The P5 Series 2s’ waterfall plot looks very clean, with no noteworthy resonances.

The total harmonic distortion (THD) of the P5 Series 2s is typical for on-ear ’phones. At the loud listening level of 90dBA (measured with pink noise), the THD rises to 2% at 20Hz, which you’re very unlikely to notice (unless you often listen to Saint-Saëns’s “Organ Symphony”). At the very loud listening level of 100dBA, the THD runs about 4.5% below 40Hz.

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. With very little reduction of level in sounds below 1kHz, and none in the “jet engine band” of about 50-100Hz, this is typical performance for passive on-ear headphones.

The impedance of the P5 Series 2s is mostly flat, staying between 24 and 30 ohms through the entire audioband.

The sensitivity of the P5 Series 2s, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 22 ohms impedance, is 101.2dB. This is typical for on-ear headphones.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 July 2015

I measured the Oppo PM-3s 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. Measurements were calibrated for ear reference point (ERP), roughly the point in space where the center axis of your eardrum would intersect with your palm if you pressed your hand against your earlobe. I moved the headphones around to several different locations on the ear/cheek simulator to find the one that produced the most bass and the most characteristic response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

This chart shows the PM-3s’ frequency response, which is just a little bit atypical in that the usual peak centered somewhere near 3kHz is more like a hill. So it’s a broader boost than usual, and the peak around 7.5kHz is a little stronger than usual. Thus, this measurement suggests a fairly neutral tonal balance but a somewhat unusual sound.

Adding 70 ohms of output impedance to the V-Can’s 5 ohms, to simulate a typical low-quality headphone amp, has essentially zero effect on the PM-3s’ frequency response.

This chart compares the closed-back PM-3s (blue trace) with Oppo’s open-back PM-2s (red trace) and NAD’s closed-back Viso HP50s (green trace). The PM-2s and HP50s obviously have flatter responses; the PM-3s are likely to be perceived as sounding more trebly than either.

The PM-3s’ waterfall plot is pretty clean, with much less bass resonance than the norm. The only noteworthy resonances in the mids and treble are centered at 2.1 and 3kHz. They’re well damped, though, and die out after about 8ms.

The Oppos’ total harmonic distortion (THD) is practically nonexistent. This is one of the lowest distortion figures I have measured in a set of headphones.

In this chart, the level of external noise is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. This result is very good for over-ear (i.e., circumaural), passive headphones, with reductions of 10dB at 1kHz, and as much as 35dB at higher frequencies. However, it won’t have much effect on jet-engine noise, which is typically loudest between 50 and 200Hz.

The PM-3s’ impedance magnitude and phase are almost dead flat at 26 ohms -- the same as Oppo’s spec.

The sensitivity of the PM-3s, measured between 300Hz and 3kHz with a 1mW signal and calculated for the specified impedance of 26 ohms, is 99.8dB -- enough to get decent volume levels from most portable devices.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 June 2015

I measured the Torque t402v 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 headphone amplifier. Measurements were calibrated for ear reference point (ERP), roughly the point in space where the center axis of your eardrum would intersect with your palm if you pressed your hand against your earlobe. 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. In measurements of the headphones with the on-ear earpad, I used the G.R.A.S. 43AG’s clamping mechanism to ensure a good seal. This was a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

This chart shows the t402v’s frequency response with the over-ear pad in the four different sound modes. The traces are color-coded to the modes: yellow for yellow mode, blue for blue mode, etc. With all modes, there’s a fairly large midrange dip between 400Hz and 1.5kHz, and the peak between 5kHz and 8kHz is stronger than the peak at 3kHz. With most headphones, the 3kHz peak is stronger. Yellow mode measured as being a lot more bassy than the other modes.

This chart shows the frequency response with the on-ear pad, again color-coded by mode. This is a much more typical response than I measured with the over-ear pad, with a mild midrange dip centered at 750Hz and a moderate (for headphones) peak at 3kHz. The magnitude of the measured differences among the modes was less with the on-ear pad.

Adding 70 ohms to the V-Can’s 5-ohm output impedance to simulate the effects of using a typical low-quality headphone amp had little effect on the t402v. This result is normalized at 1kHz, per my standard procedure. A tiny peak in the impedance produced a slight and probably inaudible boost centered at 1.1kHz, but otherwise the impedance change in the source had no effect on the frequency response.

This chart compares the t402v with on-ear pad in black mode (dark blue trace) and over-ear pad in black mode (light blue) with NAD’s Viso HP50 over-ear model (red) and Beyerdynamic’s tunable Custom One Pro with its tuning level in position 2 “linear” (green). The HP50 obviously had the flattest response of the three; in on-ear and over-ear modes, the t402v was bassier than the other two.

The t402v’s waterfall plot is very clean, with much less resonance than I usually see in headphones of this type. You can see a mild resonance at that impedance peak centered at 1.1kHz, but because it’s well damped, it dies out almost immediately. The measurement shown was taken with the over-ear pad; the result with the on-ear pad was even cleaner.

The t402v’s total harmonic distortion (THD) was moderate with the on-ear pad, but higher with the over-ear pad because of the headphone’s lower sensitivity with the latter pad. In the above chart, results with the on-ear pad are shown in the dark traces, at 90dBA (dark green) and 100dBA (dark orange); results with the over-ear pad are shown in the light traces, at 90dBA (light green) and 100dBA (light orange). With the on-ear pad, the THD is fairly typical: at 90dBA, 1% at 100Hz and 3% at 20Hz, those numbers respectively rising to 2% and 7% at the very loud listening level of 100dBA. With the over-ear pad, the results at 90dBA (still quite a loud level) were similar to the 100dBA results with the on-ear pad, but at 100dBA the distortion was pretty high. However, it’s unlikely that you could reach such high levels with the over-ear pads installed if you’re driving these headphones with a phone or tablet.

In this chart, the level of external noise is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. The green trace shows the t402v’s isolation with the on-ear pad, the purple trace the result with the over-ear pad. These results are typical for passive on-ear and over-ear headphones; you’ll get very little reduction of level in sounds below 1kHz.

The t402v’s impedance is essentially flat, averaging 18 ohms, with very moderate phase shift. As noted above, the Torque’s impedance does have a slight peak centered at 1.1kHz.

The sensitivity of the t402v, measured between 300Hz and 3kHz with a 1mW signal and calculated for the rated 16-ohm impedance in black mode, was 101.6dB with the on-ear pad and 93.9dB with the over-ear pad. The on-ear results are typical for closed-back headphones, but the over-ear results are low -- more like what I’d expect to measure from audiophile-oriented planar-magnetic headphones.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 May 2015

I measured the Phiaton MS 100 BAs 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. Measurements were calibrated for drum reference point (DRP), roughly the point at the center of the eardrum (in this case, the center of the measurement mike). I used the Phiatons’ medium-size eartips because those best fit the RA0045. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

This chart shows the frequency response of the MS 100 BAs. It’s surprisingly flat -- most earphones have a larger dip in the midrange and a bigger bump in the bass -- which suggests that the Phiatons may sound smoother, but less vivid and less exciting, than many of their competitors.

As with most headphones using balanced-armature drivers, 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 MS 100 BAs’ tonal balance. If you connect it to a high-quality source device, it has a flat response; if you connect it to a high-impedance source device (such as the headphone amps built into most laptops), the treble will be boosted a couple dB and the bass reduced by about 5dB -- easily audible differences.

The MS 100 BAs’ departure from the norm is visible in this comparison with NAD’s HP20 dynamic earphones and Sony’s XBA-H1 hybrid dynamic/balanced-armature earphones. The midrange dip visible in the NADs’ and Sonys’ responses is usually thought to produce a subjectively flatter response and a more spacious sound. However, the science here is still developing.

The Phiaton MS 100 BAs show no significant resonances above 800Hz, which is excellent performance.

The MS 100 BAs’ total harmonic distortion (THD) is relatively high; at 100Hz, it’s 2% at 90dBA and 7.5% at 100dBA. Competitors such as the Marshall Mode EQs post numbers more in the range of 1-2%. However, note that 100dBA (level measured with pink noise) is an extremely high listening level; I include it here mainly because some headphones can handle it and some can’t. Also note that research has shown that headphone distortion is rarely audible except when it’s very high.

In this chart, the external noise is at an SPL of 75dB; the numbers below that indicate the Phiatons’ attenuation of outside sounds. Their isolation is very good for earphones, reducing noise by 20dB at 100Hz (the middle of the “airplane cabin-noise band”) and by up to 32dB in the treble. Note that your results may not be as good, depending on the size and shape of your ear canals and on the size of eartips you choose.

This is the biggest impedance swing I can remember measuring in a passive headphone model: from 24 ohms in the bass to about 460 ohms at 20kHz. This is why the Phiatons’ tonal response changes so much when they’re used with a high-impedance source device.

The Phiatons’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal and calculated for the rated 24 ohms impedance, is 110.8dB, which is exceptionally high. This means that the MS 100 BAs will be able to deliver high playback levels from practically any source device.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 May 2015

I measured the Marshall Mode EQs 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. Measurements were calibrated for drum reference point (DRP), roughly the point at the center of your eardrum (in this case, the center of the measurement microphone). I used the medium-sized eartips because those best fit the RA0045. This is a “flat” measurement; no diffuse-field or freefield compensation curve was employed.

This is the frequency response of the Mode EQs in EQ1 mode. (The comparison with EQ2 mode is shown below.) This measurement may look very uneven, but it’s actually a fairly common response for earphones. The bass boost and the midrange peak at 2.5kHz are intended to compensate for the fact that the earphones effectively bypass the acoustical effects of the earlobes and ear canals.

This chart shows the Mode EQs’ frequency response in EQ1 and EQ2 modes. The response is effectively the same, except that EQ2 mode reduces bass by about 3dB.

Adding 70 ohms to the V-Can’s output impedance of 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has a modest effect on the Mode EQs in EQ1 mode (shown here), but a much larger effect in EQ2. In EQ1, the higher-impedance source shows a bass boost of about 0.5dB and, beginning above 2.5kHz, a treble rolloff of about 2dB. In EQ2, though, using a low-quality amp (like the ones built into most Windows laptops and some cheap smartphones) will soften the sound significantly, boosting bass by about 2dB and, starting at about 1.5kHz, reducing the treble by a like amount.

You can see from this chart that the Mode EQs (shown here in EQ1 mode) have a more extreme bass boost and a more extreme upper-midrange/lower-treble peak than the NAD HP20s or the Sony XBA-H1s, both of which produce comparatively neutral sounds.

The Mode EQs’ spectral decay plot shows some unusual and very narrow resonances at 6, 8, and 12kHz, and a little more bass resonance than is usual for dynamic earphones, but there’s nothing particularly troubling here.

The total harmonic distortion (THD) of the Mode EQs in EQ1 mode is insignificant, showing a slight rise around 800Hz but never rising even to 2% at the very high listening level of 100dBA.

In this chart, the sound-pressure level (SPL) of external noise is 75dB; the numbers below that indicate attenuation of outside sounds. The Mode EQs’ isolation is perhaps a little better than average for earphones, with a reduction of 10 to 30dB through most of the audioband. Note that, depending on the size and shape of your ear canals and on the eartips you choose, your results may not be as good.

Here’s why the response in EQ2 mode changes a lot depending on the output impedance of the source device. The impedance swing in EQ2 is huge for earphones with dynamic drivers, dropping from 49 ohms in the bass to 17 ohms in the treble. It’s much less extreme in EQ1 mode, which has a maximum impedance of 31 ohms. I assume that the extreme impedance shift in EQ2 mode is due to the filter used in the EQ switch.

The Mode EQs’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 30 ohms impedance, is 108.1dB in EQ1 mode, 107.0dB in EQ2 mode -- sensitive enough to get loud levels from practically any source device.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 March 2015

I measured the Oppo PM-2s using a G.R.A.S. 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. Measurements were calibrated for ear reference point (ERP): i.e., roughly the point where the axis of your ear canal intersects with your palm when you press a hand flat against your ear. This is a “flat” measurement; no diffuse-field or freefield compensation curve was used. I experimented with the fit of the earpieces by moving them around on the plate of the ear/cheek simulator, and settled on the positions that gave the best bass response and the most characteristic result overall.

The Oppo PM-2s’ response is similar to those of most of the planar-magnetic headphones I’ve measured, with one noteworthy difference. Most planar-magnetics are flat to about 1.5kHz, above which frequency their response begins to rise. The PM-2s’ response starts rising gradually at about 500Hz, which means that their midrange should sound +3 to +5dB fuller.

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, does not significantly affect the PM-2s’ response. Thus, its tonal balance will be the same from any source device. That’s especially good for these headphones, which are designed to be used with portable devices.

This comparison shows that while the PM-2s produce considerably less treble energy than the HiFiMan HE-560 or HE-400i headphones, compared to the PM-1s they have roughly +2dB more treble from 2 to 3kHz, and +3dB more from 6 to 8kHz. The PM-2s seem to strike the most even tonal balance of all four models.

The spectral-decay (waterfall) plot shows slight resonances around 2kHz. However, these are so low in level, at about -40dB, that there’s little chance you’ll hear them, especially considering that external sounds leaking in through the open backs of the earpieces will likely be much higher in magnitude.

Distortion at 90dBA from the PM-2s was almost nonexistent, except for a rise to 2% at 400Hz. At 100dBA -- an extremely loud listening level you probably couldn’t tolerate for long -- the distortion rises to 4% at 400Hz and 3% at 230Hz. (Both of these peaks correspond with peaks at the same frequencies in the impedance measurement.) I heard no distortion when I was testing the PM-2s.

For open-back headphones, the PM-2s deliver better isolation than average. There’s no isolation below 1.5kHz, but it’s -5 to -15dB from 1.5 to 10kHz. However, most closed-back models deliver isolation in the -10 to -30dB range.

The PM-2s’ impedance is almost flat, with a magnitude of 31 to 32 ohms and negligible phase shift. There are a couple of small impedance “bumps” that correspond to the peaks noted in the high-level distortion test.

The PM-2s’ average sensitivity from 300Hz to 3kHz at the rated 32 ohms measures 103.7dB. That’s +2.1dB more than Oppo’s PM-1s, and roughly in the average range of over-ear headphone sensitivity -- very impressive for planar-magnetic headphones.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 01 December 2014

I measured the NuForce Primo 8s using a G.R.A.S. 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. Measurements were calibrated for drum reference point (DRP), the equivalent of the headphones’ response at the surface of the eardrum. This is a “flat” measurement; no diffuse-field or free-field compensation curve was used. I used the medium-sized silicone eartips supplied.

The Primo 8s’ measured frequency response is unusual, and doesn’t correlate well with my perception of its tonal balance. The response below 1kHz is exceptionally flat, much like what I’ve measured from planar-magnetic headphones such as the Audeze LCD-3s -- most other earphones have a bump in the bass response. There’s a relatively mild peak at 2kHz, and above that the response rolls off quickly. Just goes to show that you need to be careful not to judge a set of headphones too strongly by its measured frequency response.

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, has a large effect on the Primo 8s’ measured response. The peak at 2kHz disappears entirely, and the treble rolloff becomes more severe by about -7dB. These earphones really demand a source with a low output impedance, at the very least a higher-quality smartphone such as an iPhone or a Samsung Galaxy S; an even better idea would be a separate headphone amp.

Compared to the Audiofly AF140 (a design with one dynamic driver and two balanced armatures) and the Sony XBA-H1 (one dynamic driver and one balanced armature), the Primo 8s show a much flatter response up to about 5kHz, but much less treble response.

The decay of the Primo 8s might look a tad messy, but this is an excellent result. First, see how clean the response is from 500Hz to 1kHz. That’s rare: Few other earphones I’ve measured can stop on a dime at frequencies between 500Hz and 1kHz. There are some long resonances at 6, 8, and 14kHz, but they’re very narrow and very low in level; there’s little chance they’d be audible.

The Primo 8s’ total harmonic distortion (THD) at 90 and 100dBA is modest. There’s a little, but this is an average to above-average result. At the loud-but-not-crazy-loud level of 90dBA, the THD below 1.5kHz is about 1%. Even at the very high level of 100dBA, THD is never higher than 3%.

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the level of attenuation of outside sounds. Probably because of the occlusion of the G.R.A.S. ear simulator by the Primo 8’s relatively large driver enclosure, the NuForces deliver outstanding isolation. They should substantially reduce jet-engine noise, considering that they attenuate outside sound by -28dB at 100Hz and -33dB at 1kHz, and by even more between 2 and 10kHz.

The impedance plots of balanced-armature headphones usually show pretty wild swings, and the Primo 8s are no exception. You can see here that they peak at 59 ohms at 550Hz, then fall to just 6 ohms at 20kHz. Phase response is also extreme: flat through much of the audioband, but dropping to -67 degrees at 1.35kHz. All the more reason to make sure you mate the Primo 8s with a high-quality source device.

The Primo 8s’ average sensitivity from 300Hz to 3kHz at the rated 38 ohms measured 116.6dB. That’s very high, and indicates that the Primo 8s will play loud as hell from even the cheapest, crummiest MP3 player.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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Parent Category: Products

Category: Headphone Measurements

Created: 15 October 2014

I measured the Level Ins 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. Measurements were calibrated for drum reference point (DRP), roughly the point at the center of the listener’s eardrum (or, in this case, the center of the measurement microphone). I used the Samsungs’ medium-size memory-foam eartip because that’s what fit the RA0045 best. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

The Level Ins’ response clearly shows the cause of the bright tonal balance I heard. The rise in the bass centered at 130Hz is normal, as is the peak centered at 3kHz (if perhaps a tad high), but the relative amount of energy between 5 and 9kHz is extremely high. My guess is that the balanced armature Samsung uses as a tweeter is set for a level about 5dB too high.

Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, usually has a large effect on earphones with balanced armatures. With the Level Ins, the effect is not large in magnitude, but it kicks the treble of an already bright-sounding headphone up another 1.5dB.

The Level Ins’ response is quite similar to that of Sony’s XBA-H1s, which I love so much, except that the Samsungs’ output between 6 and 9kHz is 5 to 10dB higher than the Sonys’. The Audiofly AF140s show more of a “boom’n’sizzle” response than either the Samsung or Sony earphones.

The Level Ins have one of the cleanest spectral-decay plots I’ve seen in any type of headphone or earphone, with near-zero resonance. I redid this measurement three times and got the same result every time; other headphones measured in the same session gave me more typical results.

The Samsungs’ total harmonic distortion (THD) is fairly average at 90dBA: typically, around 1%. But at 100dBA -- a very loud listening level -- the distortion is pretty high, and consistently so through much of the audioband, running 3 to 5% below 2kHz, then rising to 9% in a narrow peak centered on 4kHz.

In this chart, the external noise level is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. The Level Ins’ isolation is very good for universal-fit earphones, reducing noise at 1kHz by about 15dB, and reducing noise by 35dB or more between 2.2 and 11kHz at higher frequencies. Between 5 and 12kHz, the isolation is 5 to 10dB better with the memory-foam tip than with the silicone tip.

The Level Ins’ impedance is low overall, remaining below 10 ohms up to 1.5kHz, but is flatter than usual for earphones with balanced-armature drivers. The impedance phase response is also close to flat.

The sensitivity of the Level Ins, measured with a 1mW signal calculated for the specified 16 ohms impedance, is 98.2dB. That’s enough to get you a reasonable level from a portable audio player, but most of the earphones I measure deliver 6 to 10dB more output from the same signal.

. . . Brent Butterworth
brentb@soundstagenetwork.com