Reviewed on: SoundStage! Solo, May 2022
I measured the HiFiMan Deva Pro 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-04 USB Bluetooth transmitter was used to send signals from the Clio 12 QC to the headphones. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For cabled measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier. 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 Deva Pros’ frequency response with the wired connection (which is almost identical to the response in Bluetooth mode). This is extremely typical of what we see from HiFiMan headphones.
Here we can see the difference in response between the Bluetooth connection and the wired connection. The only real difference is in the bass, and even that is somewhat suspect because the Bluetooth measurement has to be gated because of the latency, and the gating can slightly throw off the measurement at the frequency extremes.
This chart shows the difference in response in wired mode when a 75-ohm source (similar to what might be experienced with some pro audio headphone amps, the amps built into cheap laptops, and some tube amps) is substituted for our usual 5-ohm source. As usual with planar-magnetic headphones, there’s effectively no difference.
In this chart, the black trace shows the right-channel wired frequency response I used for the above charts, and the other traces show how the response varied when I reseated the headphones several times on the ear-cheek simulator, and when I moved the headphones about 6mm forward, back, up, and down. You might hear some slight differences in the high treble, but overall, this is excellent consistency.
This chart shows the Deva Pros’ response in wired mode compared with the original Deva, the Apos Audio Caspian, and the Dan Clark Æon 2 headphones (all open-back designs). You can see the commonality in the HiFiMan models, and the stronger, Harman curve-ish bass response of the other models. It appears that the bass in the Devas is actually a little lower in level than the Deva Pros’ bass; however, the Deva Pros’ treble is also slightly reduced, which could have led me to the impression that they’re bassier.
The Deva Pros’ right-channel spectral-decay plot (measured with the wired connection) shows the usual super-high-Q upper midrange and lower-treble resonances we see with planar-magnetic models; these don’t appear to add tonal coloration, and they do seem to correlate with a more spacious sound.
Here’s the THD vs. frequency chart, measured using the wired connection at 90dBA and 100dBA (both levels set with pink noise). No audible distortion to worry about here.
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. The Deva Pros’ noise isolation is near zero, which suggests that there’s very little acoustical impedance on the back sides of the drivers—which seems like what open-back headphones should be going for, right?
Latency, measured with a standard SBC Bluetooth connection, typically ran about 260 milliseconds.
The impedance magnitude, measured in wired mode, is just about dead flat at 20.5 ohms, and the phase response is similarly flat.
Sensitivity, measured at 1mW and calculated for the rated 18 ohms impedance, averages 105.6dB from 300Hz to 3kHz, so any source can drive these to high levels through the wired connection.
Bottom line: I could have told what brand the Deva Pros are just by looking at the measurements. This is a classic HiFiMan design, and it doesn’t present any concerns from a technical standpoint.
. . . Brent Butterworth
brentb@soundstagenetwork.com