NOTE: This is the Bluetooth 4.2 version. Towards the end of February 2019 Astrotec has announced a 5.0 version but it was not yet available where I purchased this.
UPDATE: This review has been updated to reflect using the BT 4.2 version on the latest update of Samsung Galaxy Note 9 as of May 2019. Connectivity has been improved considerably so I can't fault Astrotec for some of these issues.
Gear tested:
Samsung Galaxy Note 9 (Exynos N960F) - AAC + SBC
Sony Xperia Z5 - SBC only
ASUS Zenbook 15 UX550GE (Intel AC 9560) - SBC
This is the second TWS earbud that I have used, after the Jabra Elite 65t. I found the Jabras to be great for utility, but their sound quality had a number of issues such as distortion and hissing on the left earbud.
Design 7/10
They use a rather generic TWS housing that is comfortable and isolates well. It looks great but isn't quite as creative as what Astrotec has done with their other IEMs. I've seen other OEM TWS that uses the exact same housing, such as the Soaiy T1S/T2 and Digihero T1, but these have dynamic rather than BA drivers and different charging cases. The shiny plastic coating around the charging case and the housings scuffs off within a rather short amount of time. After a few weeks of use, I noticed the right bud has a tendency to creak at the button, but this doesn't happen when I'm wearing them. The only major downside is it can be difficult distinguishing the left and right buds if you habitually put them on quickly.
The S60 comes in a durable charging case with a metal cap. The plastic and metal does scuff up over time but the case is quite well-built. The buds snap in magnetically for charging, but sometimes if you're too quick they won't align and charge. The connector is USB type C, which I think more TWS earbuds should be using. It's important to note that it only charges with Type C to Type A cables and not Type C to Type C. It also supports Qi Wireless charging at 5W. Unfortunately, compatibility is quite limited, as Astrotec recommends you to use 5W chargers. It works fine with my 10W wireless power bank, but for some other 10W charging pads I get a charging error. I also suspect the metal cap might trigger foreign object detection. Charging speed either way is reasonable (~1.5 hours to fully charge from approximately 25%) but I wish it supported fast charging.
ADATA CW0100 (10W) - Charging error regardless of power brick used
J5Create JUPW1101 Wireless Charging Pad (10W) - Fails to charge if plugged in to QC 2.0 or 3.0 charger. Fully functional when plugged into PC's USB 3.1 port.
Mycell MY-PC-035 Wireless Power Bank (10W) - Charges but gets very hot, especially if both the case and the buds are out of battery.
Utility 5/10
At this price point, TWS earbuds tend to be not as usable as pricier counterparts. Controls are limited to play/pause, next/previous tracks. I would have liked to see volume control (added to the Bluetooth 5.0 version) and ambient sound mode.
Call quality seems mediocre as the other side couldn't hear me clearly when I was on the bus or train.
Sound (updated impressions) 8/10
These have Knowles balanced armature drivers and have a rather warm and bassy sound. Highs are a tad rolled off while mids have reasonable clarity. The bass is quite powerful for a BA driver and you get a fairly wide soundstage with good detail retrieval. However, this is somewhat cut short by distortion that occurs with certain bass notes. Using SBC, the sound signature is largely retained, but the sound is more prone to distortion, particularly in the left driver. Both AAC and SBC exhibit some degree of hiss and clicking EMI on the left bud, albeit less severe than the Jabra 65t. On the Galaxy Note 9, the volume output is rather low, unless you go into Bluetooth settings and turn "Media Volume Sync" off and on again. This greatly increases the volume and still sounds great for AAC, but SBC becomes more badly distorted at the higher volumes. On my ASUS Zenbook 15, SBC seems to sound cleaner at higher volumes than the Note 9.
vs. Jabra Elite 65t - The Jabras are a brighter-sounding IEM and prone to sealing issues for my ears. Although I find the bass decent most of the time, they have a tendency to sound rolled off during transit.
vs. ATH-IM70. The sound is rather similar between the S60 and the IM70 in that both have an "organic" tuning that gives a lush yet reasonably detailed sound. Where they do differ is that the IM70 has more midrange emphasis, while the S60 has better detail retrieval.
Connectivity (Updated) 6.5/10
SBC connection is very reliable, and I very rarely get any sound skipping or cutouts. With the Galaxy Note 9, AAC connectivity is not very reliable. Before there was a tendency for the audio to skip every 4-5 minutes. but after the May update the connectivity has improved greatly but it still might stutter after about 15 minutes of playback, although I've had longer train rides where there's been next to no stutter. After it stutters there is sometimes a slight desync and volume imbalance between the left and right channels giving a fake stereo effect. It is definitely not a defective unit as I was able to try another pair at the store which exhibited the same behaviour. I briefly tried it with the seller's iPhone to which I noticed no connectivity issues using AAC. Connection is also quite stable using my laptop, with VERY occasional cut outs (seems to be related to the laptop itself). Regardless what codec you use there is also considerable latency. This is to be expected with TWS buds, but it is noticeably more than the Jabra Elite 65t.
Conclusion
The S60 has such high potential for its sub-100$ price point, but falls short in its utility and connectivity issues, especially on Android. Perhaps it's better to get the Bluetooth 5.0 version or wait for Astrotec's next upcoming TWS.
UPDATE: This review has been updated to reflect using the BT 4.2 version on the latest update of Samsung Galaxy Note 9 as of May 2019. Connectivity has been improved considerably so I can't fault Astrotec for some of these issues.
Gear tested:
Samsung Galaxy Note 9 (Exynos N960F) - AAC + SBC
Sony Xperia Z5 - SBC only
ASUS Zenbook 15 UX550GE (Intel AC 9560) - SBC
This is the second TWS earbud that I have used, after the Jabra Elite 65t. I found the Jabras to be great for utility, but their sound quality had a number of issues such as distortion and hissing on the left earbud.
Design 7/10
They use a rather generic TWS housing that is comfortable and isolates well. It looks great but isn't quite as creative as what Astrotec has done with their other IEMs. I've seen other OEM TWS that uses the exact same housing, such as the Soaiy T1S/T2 and Digihero T1, but these have dynamic rather than BA drivers and different charging cases. The shiny plastic coating around the charging case and the housings scuffs off within a rather short amount of time. After a few weeks of use, I noticed the right bud has a tendency to creak at the button, but this doesn't happen when I'm wearing them. The only major downside is it can be difficult distinguishing the left and right buds if you habitually put them on quickly.
The S60 comes in a durable charging case with a metal cap. The plastic and metal does scuff up over time but the case is quite well-built. The buds snap in magnetically for charging, but sometimes if you're too quick they won't align and charge. The connector is USB type C, which I think more TWS earbuds should be using. It's important to note that it only charges with Type C to Type A cables and not Type C to Type C. It also supports Qi Wireless charging at 5W. Unfortunately, compatibility is quite limited, as Astrotec recommends you to use 5W chargers. It works fine with my 10W wireless power bank, but for some other 10W charging pads I get a charging error. I also suspect the metal cap might trigger foreign object detection. Charging speed either way is reasonable (~1.5 hours to fully charge from approximately 25%) but I wish it supported fast charging.
ADATA CW0100 (10W) - Charging error regardless of power brick used
J5Create JUPW1101 Wireless Charging Pad (10W) - Fails to charge if plugged in to QC 2.0 or 3.0 charger. Fully functional when plugged into PC's USB 3.1 port.
Mycell MY-PC-035 Wireless Power Bank (10W) - Charges but gets very hot, especially if both the case and the buds are out of battery.
Utility 5/10
At this price point, TWS earbuds tend to be not as usable as pricier counterparts. Controls are limited to play/pause, next/previous tracks. I would have liked to see volume control (added to the Bluetooth 5.0 version) and ambient sound mode.
Call quality seems mediocre as the other side couldn't hear me clearly when I was on the bus or train.
Sound (updated impressions) 8/10
These have Knowles balanced armature drivers and have a rather warm and bassy sound. Highs are a tad rolled off while mids have reasonable clarity. The bass is quite powerful for a BA driver and you get a fairly wide soundstage with good detail retrieval. However, this is somewhat cut short by distortion that occurs with certain bass notes. Using SBC, the sound signature is largely retained, but the sound is more prone to distortion, particularly in the left driver. Both AAC and SBC exhibit some degree of hiss and clicking EMI on the left bud, albeit less severe than the Jabra 65t. On the Galaxy Note 9, the volume output is rather low, unless you go into Bluetooth settings and turn "Media Volume Sync" off and on again. This greatly increases the volume and still sounds great for AAC, but SBC becomes more badly distorted at the higher volumes. On my ASUS Zenbook 15, SBC seems to sound cleaner at higher volumes than the Note 9.
vs. Jabra Elite 65t - The Jabras are a brighter-sounding IEM and prone to sealing issues for my ears. Although I find the bass decent most of the time, they have a tendency to sound rolled off during transit.
vs. ATH-IM70. The sound is rather similar between the S60 and the IM70 in that both have an "organic" tuning that gives a lush yet reasonably detailed sound. Where they do differ is that the IM70 has more midrange emphasis, while the S60 has better detail retrieval.
Connectivity (Updated) 6.5/10
SBC connection is very reliable, and I very rarely get any sound skipping or cutouts. With the Galaxy Note 9, AAC connectivity is not very reliable. Before there was a tendency for the audio to skip every 4-5 minutes. but after the May update the connectivity has improved greatly but it still might stutter after about 15 minutes of playback, although I've had longer train rides where there's been next to no stutter. After it stutters there is sometimes a slight desync and volume imbalance between the left and right channels giving a fake stereo effect. It is definitely not a defective unit as I was able to try another pair at the store which exhibited the same behaviour. I briefly tried it with the seller's iPhone to which I noticed no connectivity issues using AAC. Connection is also quite stable using my laptop, with VERY occasional cut outs (seems to be related to the laptop itself). Regardless what codec you use there is also considerable latency. This is to be expected with TWS buds, but it is noticeably more than the Jabra Elite 65t.
Conclusion
The S60 has such high potential for its sub-100$ price point, but falls short in its utility and connectivity issues, especially on Android. Perhaps it's better to get the Bluetooth 5.0 version or wait for Astrotec's next upcoming TWS.