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Reviewed on: SoundStage! Solo, November 2019

I measured the Frees using laboratory-grade equipment: a G.R.A.S. 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. 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 earphones. If you’d like to learn more about what our measurements mean, click here.

Frequency response

The above chart shows the Frees’ frequency response measured with the RA0402 ear simulator (I wasn’t able to get an adequate seal using the KB5000 and KB5001 simulated pinnae). This is pretty much a “by the book” response for good-sounding earphones, and it’s the first time I’ve seen this in a set of true wireless earphones.

The impulse response shows that the latency with the MEE Connect is 283ms. This is typical for true wireless earphones, and it means you will almost certainly notice lip-sync errors when you watch videos using the Frees. Best to stick to music and podcasts with these.

Frequency response

This chart shows the Frees’ right-channel response compared with two other true wireless earphones (HiFiMan TWS600s and Sennheiser Momentum True Wirelesses), as well as with the AKG N5005s, the earphones said to best reflect the Harman curve. The Frees are at least in the ballpark of the Harman curve; they’re likely to sound a little softer than the AKG N5005s, and because their bass resonance is centered at a higher frequency of 80Hz, they’re likely to sound a tad soft, at least relative to the AKGs.

THD

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. While distortion is very low at all frequencies and levels, note that I couldn’t get the Frees to play loud enough (at least when fed by the MEE Connect transmitter) to do a measurement at 100dBA.

Isolation

This chart shows the Frees’ isolation versus a couple of other true wireless models (1More E1026BT-1 Stylish and Sennheiser Momentum True Wireless earphones) and a passive (wired) model with a foam tip (Campfire Comet earphones). The Frees’ isolation is excellent for a true wireless earphone without active noise canceling, and it actually comes pretty close to the isolation of some models with active noise canceling.

. . . Brent Butterworth
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