Reviewed on: SoundStage! Solo, April 2022

I measured the Grell Audio TWS/1 earphones using laboratory-grade equipment: a GRAS RA0402 ear simulator 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, and added the KB5000/KB5001 simulated pinnae with the full Model 43AG ear/cheek simulator. I used two different Bluetooth transmitters—a Reiyin WT-04 USB and a MEE Audio Connect—to send signals from the Clio 12 QC to the earphones. Due to the complications introduced by the ever-changing latency of the Bluetooth transmitter, I used FFT spectrum analysis for some measurements. This looks somewhat different. Because of the complications of measuring these, and the various unusual modes on them, this presentation will be somewhat different from the norm for this site. 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.

I started out by measuring the maximum volume of the TWS/1s, compared with the Denon AH-C830NCW and the Jabre Elite Active 65t earphones (two other true wireless models), using -10dBFS pink noise and A-weighted metering with Room EQ Wizard. The level was 92.2dBA with SoundID off and 99.6dBA with SoundID on. In comparison, I measured a maximum volume of 100.3dBA for the Jabras and 100.6dBA for the Denons.


This chart shows the frequency response of the TWS/1s, right channel, with SoundID on and off. You can see that the black line (SoundID) looks fairly typical for dynamic-driver earphones. SoundID—tuned for my ears—boosted the response a little at about 5.5kHz, and a lot at about 12kHz, which are both pretty good decisions, based on my most recent audiograms. They also add a lot of upper bass and lower midrange, between about 100 and 700Hz. I don’t have any hearing loss in this range (hearing loss in this range is rare), so I assume this is to sculpt the earphones’ sound to meet the SoundID profile.

But notice how much higher the volume is with SoundID on: an average of 5.97dB higher between 20Hz and 20kHz. This is bogus; it makes legitimate, level-matched comparisons between SoundID and the unprocessed sound practically impossible for average listeners. I wouldn’t use the word “bogus” if I weren’t convinced that every audio scientist alive would agree with me. I understand that level-matching two different EQ profiles is almost impossible to do with complete certainty, but clearly there was no intent here to make the comparison legitimate.

Noise canceling

Here we can see the difference in frequency response with noise canceling on and off. There’s very little difference, which is admirable.

Frequency response

This chart shows the right-channel response of the TWS/1s (with SoundID off) compared with a couple of other true wireless models, and with the Sennheiser IE 300s, a set of passive earphones I like. The TWS/1s, in their native voicing, have the most “normal”-looking response, and it’s not too far off the Harman curve.


I thought I had heard some distortion in the TWS/1s, but it doesn’t look from the measurements like this is a real concern—the distortion is very low even at the very loud level of 99.3dBA (measured with pink noise). Normally I would use 100dBA but I couldn’t get the TWS/1s to play that loud.


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. We’ll start by showing the differences among the earphones’ listening modes. Interestingly, the NAR function—which according to my listening works very well in not-so-loud surroundings—doesn’t seem to do a lot in the presence of loud noise. But it probably shouldn’t, because the sounds it’s trying to eliminate would likely be masked. This performance is consistent with the way Grell describes the function—it seems intended primarily to reduce high-frequency noise in relatively quiet environments.


This chart shows how the TWS/1s’ noise canceling performs compared with some other leading true wireless models with noise canceling. It may not look all that impressive compared with some of the others, but in my experience, the roughly 15dB of noise canceling the TWS/1s offer is plenty enough to make listening to music much easier and more pleasant on airplane flights.


Whether I used the Reiyin or MEE transmitter—both of which have aptX Low Latency, but not aptX Adaptive, which the TWS/1s use—latency jumped around between about 220 and 270ms. So you’ll probably notice a bit of latency when watching movies or playing games on your phone, but it depends on the phone.

Bottom line: Other than the annoying level jump when SoundID is turned on, the Grell TWS/1s seem to have no notable technical issues.

. . . Brent Butterworth