Synchros S300i is effectively a fully wired version of the wireless S400BT. While the designs aren’t completely identical, they have a lot in common: plasticky circular earcups that straddle the line between “on-ear” and “over-ear” by using soft padded cushions to isolate your canals, held together with a padded steel headband that has 12 ratchet-locked steps of adjustability per side. This model’s JBL branding is thankfully much smaller than S400BT’s, but the combination of metal and plastic components is otherwise highly similar, albeit here with four different color combinations — red or blue with black or white — to choose from. (JBL’s site claims six color options but doesn’t show the other two; we would suspect they’re all black or all white, which would be better than the somewhat cheap-looking colored accents on the other models.) An accent color-matched detachable cable includes a just-slightly-too-high three-button remote and microphone unit, as well as a detachable shirt clip. S300i’s zippered carrying case is much like S400BT’s, as well.
Our review of the then-$300 Synchros S400BT had one primary complaint: we mentioned that the sound was bass- and midrange-forward, with respectable rather than pronounced treble, and no major distortion issues. Although we described the sound as “quite good,” we noted that it was on par with and therefore not worthy of a $100 premium over a rival pair of Bluetooth headphones from Scosche. That problem has effectively been resolved with Synchros S300i: you’re getting the same basic sonic performance at half the S400BT’s original price, and losing only Bluetooth functionality in the process. While the audio drivers in Synchros S300i haven’t been ideally optimized — they open up their mids and highs only above the 50% volume mark — they sound good enough for $150, and will be appreciated by fans of bassy music.
AKG’s K845BT is a different story — it’s effectively what the Synchros S400BT should have been for $300. While the basic design elements aren’t terribly different between those models, AKG’s little implementation details are better: K845BT makes good use of metal, has fewer and cleaner lines, and the earcups are larger. While the size difference isn’t night and day, AKG’s earcups do actually surround your ears fully rather than resting the “protein leather” pads on your outer ears, reducing pressure and discomfort during longer listening sessions. The AKG branding is far less conspicuous, and you still get the micro-USB recharging cable and 3.5mm audio cable in the package. All you give up relative to S400BT is a carrying case; K845BT’s earcups swivel inwards to fold flatter, but aren’t designed to further compact or really be carried around. This lack of travel-readiness is really the only way in which AKG’s version falls behind JBL’s.
That’s something of a shame, because K845BT is otherwise really fun to use on the go. The wireless range we achieved between the headphones and an iPhone 5s was remarkable — we were able to walk four rooms away, complete with obstructions, before we noticed any breakup in the audio signal. On the other hand, K845BT’s controls are somewhat limited; AKG has dispensed with the gimmicky gesture controls found on S400BT in favor of simple volume, play/pause, and power buttons hidden underneath the right earcup. There are no Siri or track controls, which might be an issue if you plan to walk far away from your iOS device with the headphones on. Although the adjacent integrated microphone does work for phone calling, callers described us as a little muffled by comparison with the neck-mounted mics in Apple’s cabled earphones — not bad, just not as clear.
Sonically, K845BT delivers a better wireless experience than S400BT: rather than skewing bass-heavy, AKG’s audio is balanced, with cleaner and more obvious treble offset by ample but more controlled bass. The 50mm drivers inside K845BT are larger than S400BT’s 40mm drivers, and the extra size actually helps here, reducing the dynamic range strain we sometimes hear when little speakers try to do more than they’re capable of. By Bluetooth headphone standards, the audio is most noteworthy because it sounds clean; only when audio goes completely silent will you briefly notice a tiny amount of amplifier noise. Imperfect though it may be, AKG definitely has static under control.
Both Synchros S300i and K845BT merit our strong general recommendation, but for different reasons. Synchros S300i is a pretty close to right-priced over-ear/on-ear wired headphone, with good sound, solid remote and mic performance, and travel convenience all on its side. While it’s not the best headphone of its type we’ve ever tested — Scosche’s RH656m/md still stands out in this regard — it’s a solid option that some users may prefer on comfort or bassy sonic balance. By contrast, K845BT sells for twice the price but delivers a markedly better experience in a variety of ways — superior sound quality, comfort, and some of the best wireless performance we’ve found in a Bluetooth headphone.