Reviewed on: SoundStage! Solo, October 2018
I measured the Elegias 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 Elegias’ frequency response measured with the new KB5000 and KB5001 anthropomorphic simulated pinnae. This is the best match I was able to achieve between the left and right channels. They match very closely in the midrange, where it counts most. There is a pretty big difference in the bass, which I have to suspect may be due to the way the earpads seal on the face of the ear/cheek simulator (which has to be turned 180 degrees when doing left-ear measurements), but the bass response you see here was very consistent as I moved the headphones around on the simulator, and I usually get a better match than this. Caveats aside, this is an unusual measurement in that the peak in the 3kHz region (which is generally considered to make headphones sound more like speakers in a room) is very mild, only about 4dB above the response at 500Hz; often, the peak is more like 12dB above the 500Hz response.
This chart shows the Elegias’ 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.
Here you can see how the Elegias’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop or some cheap professional headphone amps. It’s a significant effect; the higher-impedance source produces a broad boost that maxes out at 2.6dB at 90Hz, enough to audibly tilt the tonal balance (and in a way I think would likely be to most people’s taste).
This chart shows the Elegias’ right-channel response compared with two other high-end closed-back headphones (the Audeze LCD-XCs and the MrSpeakers Æon Flows with their two-hole white filter installed), 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-XCs. You can see how unusually flat the Elegias’ response is here.
The Elegias’ spectral decay (waterfall) chart shows a fairly strong resonance at 3.2kHz, which doesn’t seem to correspond to any particular feature of the frequency response. It’s well-damped, though, and nearly gone after about 5ms.
Measured total harmonic distortion (THD) of the Elegias is almost non-existent above 150Hz, and barely breaches 2% in the bass even at the extremely loud level of 100dBA.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The Elegias’ isolation is very good for a passive closed-back model, generally beating the MrSpeakers Æon Flows and easily beating the smaller NAD Viso HP50s. I threw in the Focal Clear isolation measurement to show the advantage in isolation gained by the closed-back design of the Elegias.
The Elegias’ impedance response is typical for closed-back, dynamic-driver headphones, with the impedance generally hovering close to the rated 35 ohms and rising to 57 ohms peak at the 70Hz system resonance. The phase response is fairly flat for large dynamic-driver headphones.
The sensitivity of the Elegias, measured between 300Hz and 3kHz with the leatherette pads using a 1mW signal calculated for 35 ohms impedance, is 102.9dB. That’s quite high for audiophile-oriented headphones, and it should be enough to get loud volumes from almost any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, April 2023
I measured the Campfire Audio Orbit earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. A Reiyin WT-HD06 Bluetooth transmitter was used to send signals from the Clio 12 QC to the earphones. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. Note that I’m unable to do spectral-decay measurements with most Bluetooth earphones because of the latency. If you’d like to learn more about what our measurements mean, click here.
This chart shows the Orbits’ frequency response. See that peak around 5.5 to 6kHz? If you shifted that down by 2.5kHz, this response would look fairly normal. I’m sure that sometime in the last ten years I’ve measured something with a response that looks like this, but I can’t recall what it was or what it sounded like. My guess is that these earphones will sound recessed in the upper midrange, which is where the definition and clarity of human voices happen.
This chart shows the Orbit earphones’ response compared with three true wireless models that have gotten good reviews here. (Models with noise canceling are measured with noise canceling activated.) Note that the KEF Mu3 earphones come pretty close to the Harman curve. It’s easily apparent how much less upper-midrange energy the Orbits have versus the other earphones.
Here’s the THD vs. frequency, measured at 90dBA; I could barely get the Orbits to play any louder. Note that I used discrete sine test tones in one-octave steps rather than my usual sine sweep, because I wasn’t able to find a combination of settings on the Clio analyzer that could compensate for the Bluetooth latency. The distortion is very high at 20Hz, but it’s down to inaudible levels by 40Hz, and very few music recordings have much content below 40Hz. It’s also fairly high at 10kHz, but considering that the first distortion harmonic will be at 20kHz, you won’t hear it.
In this chart, the external noise level is 85dB SPL (the red trace), and the numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. Weirdly, in the simulated pinna of the ear/cheek simulator, I got better isolation with the supplied silicone tips than with the supplied foam tips, but in a real ear, the results may be different. I added the Bose QC Earbuds II to show how a good set of noise-canceling earphones compares.
Latency, measured with the Reiyin transmitter, was typically around 245ms.
Bottom line: The Orbit earphones definitely have a quirky frequency response, which research suggests the majority of listeners probably won’t dig, but Campfire intentionally doesn’t conform to any one target curve, and crafts different sonic profiles for its earphones. It’s up to the listener to decide whether they like this sound.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, March 2023
I measured the Sennheiser Momentum 4 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. A Reiyin WT-HD06 Bluetooth transmitter was used to send signals from the Clio 12 QC to the headphones. A Samsung Galaxy S10 smartphone served as a source for certain measurements. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the Momentum 4 headphones’ frequency response in Bluetooth mode with noise canceling on full. There’s nothing really out of the ordinary here. The left- and right-channel measurements don’t match all that well; this could be the result of the gating needed to overcome Bluetooth’s latency, but I tried many times to get them to match, and couldn’t.
This chart (done using the Clio’s FFT function with white noise, so it looks somewhat different) shows the difference in response with the noise canceling on and off, Transparency mode, and with a wired connection with power off. Admirably, the noise canceling has no effect on the frequency response. However, Sennheiser doesn’t seem to have put any work into acoustical tuning, because the wired response with power off (which can’t exploit the internal digital signal processing) is a mess—adequate for plugging into an airplane seat and watching old Seinfeld episodes, but not in any case where you care about what the material sounds like.
This chart shows the Momentum 4 headphones’ response compared with a few competitors, all in Bluetooth mode with noise canceling on—except for the AKG K371s, which I’m using as a Harman curve proxy. The Momentum 4s seem a little light in the midrange, but otherwise largely in the ballpark with other good noise-canceling headphones.
The Momentum 4 headphones’ right-channel spectral-decay plot (measured with the wired connection) has a bit of resonance in the bass, but it’s well-damped and basically gone in a few milliseconds.
Here’s the THD vs. frequency, measured using the wired connection at 90dBA and 100dBA (both levels set with pink noise). The distortion gets pretty high in the bass, but only at extremely loud levels, and bass distortion is much less audible because the distortion harmonics are well below the human ear’s range of greatest sensitivity.
In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. I threw in the Momentum 4s’ Transparency mode, which, strangely, doesn’t seem to let in much sound above 1kHz. The Momentum 4s’ noise canceling isn’t the best, but it’s pretty close to the best.
Note that the transmitter showed it was in aptX Low Latency mode. The headphones are equipped with aptX and aptX Adaptive.
The impedance magnitude, measured in wired mode with power off, measures about 75 to 80 ohms up to 1kHz, and then falls to a minimum of about 52 ohms, with a corresponding electrical phase shift.
Sensitivity with the wired connection, power off, averaged between 300Hz and 3kHz, with a 1mW signal calculated for the rated 80 ohms impedance, is 105.6dB, plenty high enough to get loud levels from any source.
Bottom line: The Momentum 4 headphones’ measured performance looks good, with a pretty safe and sane frequency response and very good noise canceling. The only sore spot is the wackadoodle frequency response in wired/power-off mode.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, January 2023
I measured the Focal Utopia 2022 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and a Clio 10 FW audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. The headphones were amplified using a Musical Fidelity V-CAN. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
The above chart shows the Utopia 2022s’ frequency response. This is fairly ordinary for audiophile headphones, but for two anomalies. First, that unusual little peak at about 1.4kHz, (also seen in the original Utopias), which will likely add a slight emphasis in the upper midrange. Second, the low energy above 8kHz, which isn’t surprising after hearing how the Utopia 2022s seem to damp extreme high-frequency sounds.
This chart shows how the Utopia 2022s’ tonal balance changes when they’re used with a high-impedance (75 ohms) source, such as a cheap laptop or some cheap professional headphone amps, or some tube amps. There’s a substantial bass boost with the high-impedance source—about +3.5dB, centered at about 65Hz—so these may get bassier when used with an amp that has a tube output stage.
This chart shows the Utopia 2022s’ right-channel response compared with the original Utopias and two other well-regarded high-end models: the Meze Elites (used with the supplied Alcantara earpads) and the Sennheiser HD 800 S headphones. You can see how the Meze and Sennheiser models have more energy in the top octave-and-a-half.
Just as with the original Utopias, the Utopia 2022s’ spectral-decay plot looks like the plots I see with planar-magnetic headphones, with a lot of very high-Q resonances between about 1 and 5kHz. That’s weird because planar drivers are flat, but the Utopia 2022s’ drivers are M-shaped. I associate these resonances with a nice sense of space, rather than an audible coloration, but to my knowledge, there’s no science on that—although a famous audio scientist was the one who gave me the idea.
There’s a little bit of distortion in the deep bass with the Utopia 2022s at very high levels, but you’ll never hear it because the distortion harmonics are still well below the most sensitive range of human hearing.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. The isolation of the Utopia 2022s, like that of most open-back headphones, is negligible. I added the original Utopias so you could see the effects of the changes in the outer grille (it does look like the new one is somewhat more transparent at high frequencies), and the Focal Stellias so you can see how a closed-back model compares.
The Utopia 2022s’ impedance is mostly flat at the rated 80 ohms for about 6.5 octaves, but then it takes a huge swing up to 770 ohms at 52Hz—which shows there’s been a change in the voice coil, because the old model rose only to 655 ohms. There’s also a big phase swing in the bass, corresponding with the impedance peak. This is why these headphones will sound different with high-impedance sources.
Sensitivity of the Utopia 2022s, measured between 300Hz and 3kHz, using a 1mW signal calculated for 80 ohms rated impedance, is 105.6dB—exactly the same as the original model, and no problem for any source device to drive.
Bottom line: There are a couple of unusual frequency-response characteristics with the Utopia 2022s, and definitely not a strong upper-treble response, but the engineering otherwise seems solid, with particular praise for the sensitivity, which is way high for high-end headphones.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, January 2023
I measured the Akoustyx S-6 earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. The earphones were amplified using a Musical Fidelity V-CAN amplifier. Except as noted, I used the supplied medium-sized silicone tips for all measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the S-6es’ frequency response. This is a very “smiley” response, with sharply boosted low bass and, especially, treble. I’d expect the midrange to sound recessed in comparison.
This chart shows how the S-6es’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop, some tube amps, or some professional headphone amps. There’s just a small difference, a boost of about 1dB above 5kHz.
This chart shows the S-6es’ right-channel response compared with various earphones, including the AKG N5005s, which are said to be the passive earphones that come closest to the Harman curve. You can easily see how far outside the norm the S-6 earphones’ response is.
The S-6es’ spectral-decay plot looks mostly clean; there’s some bass resonance, but it’s well-damped and down by about 40dB after the first few milliseconds.
The S-6es’ harmonic distortion is mostly low; there’s a little bit of a rise between about 1 and 3kHz, but even at the crazy-loud level of 100dBA, it’s still below 2 percent.
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. In the 43AG ear/cheek simulator, the S-6es offer a fairly modest amount of isolation with just the silicone tips, but if you add the silicone wings and use the foam tips, the isolation is truly outstanding.
The impedance curve of the S-6 earphones runs about 16 ohms up to about 2kHz, but above 5kHz, it starts to dive, ending up at 10 ohms at 20kHz; that’s why the response at these frequencies is down about 1dB with a high-impedance source. The phase takes a similar dive.
Sensitivity, measured in the right channel between 300Hz and 3kHz, using a 1mW signal calculated for 18 ohms rated impedance, is 102.9dB. That’s high enough that no portable device should have problems getting the S-6es to play as loud as you want.
Bottom line: The basic engineering of these earphones looks solid, but the frequency response shows extreme treble and low-bass boost, which I have to think will sound unnatural, even though decades of audio history suggests some listeners will probably enjoy it.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, January 2023
I measured the Moondrop Quarks earphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. The earphones were amplified using a Musical Fidelity V-CAN amplifier. Except as noted, I used the supplied medium-sized silicone tips for all measurements because they fit best in the ear simulator. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the Quarks’ frequency response. This is within the norm for this type of product, although the peak at 3kHz is much higher-Q (i.e., narrower) than normal, and there’s a little less bass than usual, plus a little less oomph in the top two octaves (5 to 10kHz and 10 to 20kHz) of treble. The left channel is also consistently more sensitive than the right, with about 1.5dB more output for the same input voltage. I generally don’t notice mild imbalances like these, but some people might on certain recordings.
This chart shows how the Quarks’ tonal balance changes when they’re used with a high-impedance source, such as a cheap laptop, some tube amps, or some professional headphone amps. There’s no difference, so the Quarks will perform consistently with different source devices.
This chart shows the Quarks’ right-channel response compared with various competitors, including the AKG N5005 earphones, which are said to be the passive earphones that come closest to the Harman curve. The Quarks’ quirks are mild, as I described above.
The Quarks’ spectral-decay plot looks very clean, with no audible resonances.
The Quarks’ harmonic distortion is low, even at the mega-cranked level of 100dBA (measured with pink noise).
In this chart, the external noise level is 85dB SPL, and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. In the 43AG ear/cheek simulator, the Quarks offer a typical level of isolation for compact earphones, although less isolation above 2kHz than a couple of (much more expensive) competitors offer.
The impedance curve of the Quarks is almost entirely flat at 15 ohms, and the phase response is also flat.
Sensitivity, measured in the right channel between 300Hz and 3kHz, using a 1mW signal calculated for 16 ohms rated impedance, is 93.1dB. That’s very low for earphones. So some portable source devices might have problems getting the Quarks to play as loud as you want with some recordings.
Bottom line: The measurements show some compromises in the Quarks’ performance, which has to be expected in a set of earphones this inexpensive. But other than the very low sensitivity, there’s nothing here that would likely pose a problem. For the price, the safe’n’sane frequency-response tuning is surprising and impressive.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, December 2022
I measured the Crosszone CZ-10 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the frequency response of the CZ-10s’ right- and left-channel drivers only, without the contribution of the crossfeed drivers. (This is what I think will show what the tonal balance of these headphones looks like; adding in the contribution of the crossfeed drivers might sound good to the ear, but the cancellation effects will just look bizarre to a microphone.) This isn’t too crazy a response, considering how unusual the design is. The response is definitely weak in the top two octaves of treble. The bass, while it looks adequate, certainly doesn’t appear to be what you’d call bumping—but more on this later. The peak at around 2.8kHz is common, although its high Q means it covers about 1/4 octave, where usually this peak would cover about a full octave. So this probably wouldn’t sound too unusual, but it definitely wouldn’t sound airy.
This chart shows the right-channel response from above, with the response of the left-channel crossfeed driver in the same earcup of the headphone. The contribution of the crossfeed driver peaks between 1 and 2kHz, but at higher frequencies, the contribution (and, I assume, the spatial effects) won’t be strong.
Here we can see the difference in the CZ-10s’ response when a high-impedance (75 ohms) source is substituted for a typical low-impedance source (5 ohms). The difference is negligible, so as long as the amp has enough power to drive the CZ-10s, it shouldn’t affect their sound.
This chart shows the CZ-10s’ right-channel-only (no crossfeed driver) response compared with two closed-back models (the Beyerdynamic T5 3rd Generation and AKG K371 headphones) and an open-back model (the HiFiMan Sundara headphhones). All are normalized to 94dB at 500Hz. In this chart, the CZ-10s certainly seem bass-deficient, but they didn’t sound that way; my guess is that the left-channel crossfeed driver is in phase with the right-channel drivers at low frequencies, and thus elevates the overall bass level.
The CZ-10s’ spectral decay—i.e., resonance plot—shows a pretty strong resonance centered at 2.8kHz, the same frequency as the peak in the frequency response. But it’s well-damped, and totally imperceptible after just 10ms.
Here’s the THD vs. frequency chart, measured at 90dBA and 100dBA, both levels set with pink noise, using just the right-channel drivers with no crossfeed driver. There’s some observable distortion in the bass, which isn’t unusual for dynamic drivers, but considering that it’s below 4% THD even at the insanely loud level of 100dBA, I’d be very surprised if it’s audible.
In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The CZ-10s’ isolation is almost the same as all the other models included here.
The impedance of the CZ-10s takes a big plunge, running about 85 ohms in the bass but plunging to below 30 ohms in the treble. There’s a corresponding phase swing (apologies for exaggerating the phase shift; my scale is usually +180 to -180 degrees). I’m surprised, given this result, that there wasn’t more of a change when I went from the 5-ohm source above to the 75-ohm source.
Sensitivity of the CZ-10s, calculated for 75 ohms rated impedance, using all of the drivers in the right earpiece and averaged from 300Hz to 3kHz, is 100.9dB with a 1mW signal. That’s not terribly low, but low enough that you may not get enough volume if you plug these straight into a smartphone or tablet.
Bottom line: It’s tough to judge headphones like this based on conventional measurements, because they’re about how the contributions of the different drivers add up at the eardrum and are interpreted by the brain. I can confidently say that the Crosszone CZ-10 headphones are lacking in high-frequency response, but that’s the only clear flaw I can see in the measurements.
. . . Brent Butterworth
brentb@soundstagenetwork.com
Reviewed on: SoundStage! Solo, December 2022
I measured the Sivga Oriole headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
This chart shows the Orioles’ frequency response, which shows some weird stuff. That dip centered near 200Hz looks scary, especially considering that it’s about an octave wide, although I should note that response dips are less audible than peaks, if the magnitude and Q are comparable. However, above about 500Hz, they’re not very far off the Harman curve—but there’s a lot less energy below 500Hz than the Harman curve recommends.
Here we can see the difference in the Orioles’ response when a high-impedance (75 ohms) source is substituted for a typical low-impedance source (5 ohms). It’s just a 1dB bump in the bass with the high-impedance source, which would be at most barely noticeable.
This chart shows the Orioles’ right-channel response compared with the open-back Sivga P-IIs, the HiFiMan Sundara Closed-Backs, and the AKG K371s (one of the headphones said to come closest to the Harman curve). All are normalized to 94dB at 500Hz. Clearly, the Orioles are outside the norm in some ways.
The Orioles’ spectral decay—i.e., resonance plot—shows a pretty strong resonance centered at about 500Hz, but it’s got a very high Q (i.e., narrow bandwidth), so I doubt it’ll be very noticeable. There’s another resonance centered at about 4kHz; it’s better-damped, but it might result in a slightly bright sound at times.
Here’s the THD vs. frequency chart, measured at 90dBA and 100dBA, both levels set with pink noise. There’s some observable distortion in the bass at very high levels, and certainly more than you’d likely get with a planar-magnetic driver. But considering that it’s only about 2% THD at the loud level of 90dBA, I doubt it’d be audible.
In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The Orioles’ isolation is excellent, delivering what should be an audibly quieter experience than the other two closed-back models included in this chart. I threw in the Sivga P-II headphones so you could see how an open-back design compares.
The impedance of the Orioles is nearly flat at about 35 ohms through most of the audio range, with a rise and corresponding phase-response wrinkle centered at 45Hz, which is typical of a dynamic driver. That rise is the cause of the difference in frequency response when the Orioles are used with a high-impedance source, but considering that it’s only about a 1dB bump in the bass, it’s nothing to be concerned about.
Sensitivity of the Orioles, calculated for 32 ohms rated impedance and averaged from 300Hz to 3kHz, is 106.8dB with a 1mW signal, which is plenty high enough that any source device should be able to drive these headphones to loud levels.
Bottom line: The Oriole headphones’ engineering looks solid, and you can certainly drive them with any conceivable source device. However, the frequency response is idiosyncratic. Whether you’ll dig it, I can’t say, but I’d recommend you hear them before you buy, or buy them from a merchant that accepts returns.
. . . Brent Butterworth
brentb@soundstagenetwork.com