Reviewed on: SoundStage! Solo, December 2019
I measured the Liberty 2 Pro earphones using laboratory-grade equipment: a G.R.A.S. RA0402 ear simulator and a Clio 10 FW audio analyzer. For isolation measurements, I added a G.R.A.S. Model 43AG ear/cheek simulator and KB5000 simulated pinnae, and used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. A MEE Audio Connect Bluetooth transmitter was used to send signals from the Clio 10 FW to the earphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. Note that because of the latency introduced by Bluetooth, I wasn’t able to do a spectral-decay measurement, and of course my usual impedance and sensitivity measurements are irrelevant for wireless headphones. If you’d like to learn more about what our measurements mean, click here.
The above chart shows the Liberty 2 Pro earphones’ frequency response measured in Soundcore Signature mode with the RA0402 ear simulator. This is what’s often called a “smiley” response because the bass and treble are more elevated than usual relative to the midrange.
The impulse response shows that the latency with the MEE Connect is 268ms. This is typical for true wireless earphones, and it means there is a significant chance you will notice lip-sync errors when you watch videos using the Liberty 2 Pros.
Here you can see the response of the Liberty 2 Pros in Soundcore Signature mode and in Flat mode. In this case, the low-frequency response is simply shelved down, which is a good thing -- typically, broad and gentle EQ adjustments sound better than lots of narrow and extreme EQ adjustments.
This chart shows the Liberty 2 Pros’ right-channel response in Soundcore Signature mode compared with two other true wireless earphones (EarFun Frees and Sennheiser Momentum True Wirelesses), as well as with the AKG N5005 earphones, which are said to best reflect the Harman curve. Though all these earphones (and to the best of my memory, all earphones I’ve measured) show stronger output in this measurement in the bass and treble relative to the midrange (at about 800Hz), the Liberty 2 Pros’ response is more extreme in this respect.
Because of the latency of the Bluetooth connection, I could not use Clio’s sine sweep function to measure total harmonic distortion (THD) versus frequency, so I did discrete THD measurements of sine tones in one-octave steps. Distortion here is extremely low, and it’s worth noting that the Liberty 2 Pros did play loud enough (at least when fed by the MEE Connect transmitter) to do a measurement at 100dBA.
This chart shows the Liberty 2 Pro earphones’ isolation with the black and red supplied tips versus a couple of other true wireless models (EarFun Frees and Sennheiser Momentum True Wirelesses). The Liberty 2 Pros’ isolation looks like that of a conventional set of passive earphones; the EarFun Free earphones do a better job here probably because their design is more ear-filling, while the Liberty 2 Pros seem to stick out more.
. . . Brent Butterworth
brentb@soundstagenetwork.com
