Expected to ship in mid-March, JBL’s Synchros S400BT ($300) is the audio company’s latest set of Bluetooth wireless headphones. Shipping along with a carrying case, audio cable, and USB charging cable, the earcups straddle the line between large on-ear and small over-the-ear style. Physically well-built and very comfortable, it’s appealing in terms of audio performance, which is the most important factor in evaluating headphones. There are a few oddities that detract from the appeal, though, and that’s before you consider the very high price.
In building Synchros S400BT, JBL used a a very nice combination of metal, plastic, and what seems to be faux leather for both the the earcups and padding inside the adjustable stainless steel headband. Each side of the band can slide to adjust to 14 different levels of fit. While they click into place each step of the way, there’s no real resistance, and the earcups don’t ever really feel tight as a result.
For travel, the cups fold in on the band, folding to lay flat in the same direction. From a comfort standpoint, we really liked the way the headphones felt, even after extended periods, thanks in part to the padding. However, the cups themselves are noticeably bulky, each about 2” thick, and although they have a battery inside promising “extended playback time,” JBL doesn’t list exactly how long Synchros S400BT will last per charge.
All of the controls and inputs are built into the left earcup. In addition to the power and Bluetooth pairing buttons, there’s the audio/power-in port — narrower than standard 3.5mm plugs — and a small microphone opening. Hidden touch-sensitive controls on the outside of the cup itself allow you to start and stop playback, adjust the volume, and move back and forth among your songs. While it’s a nice concept, we found the controls to be far too sensitive in some regards, and picky in others.
Accidentally brush your hand against the surface and you may pause whatever is playing, an issue that came up a few times during testing. Then, unless you swipe your finger properly across the unmarked cup’s surface, the volume won’t change. This is a perfect example of why gimmicky capacitive controls shouldn’t replace physical buttons on headphones.
To test Synchros S400BT’s audio performance, we compared it against the RH1060 Realm Bluetooth Headphones from Scosche. Although JBL’s headphones cost $100 more, the difference in performance between the sets — both of which use 40mm drivers — is negligible. That’s not necessarily terrible, as S400BT sounds quite good—bass- and midrange-forward, with respectable rather than pronounced treble, and no major distortion issues. With such a price gap, however, we’d expect a sizable improvement in audio quality, and there just isn’t one: they have very similar dynamic ranges, and particularly when they’re used in wired mode, Scosche’s headphones offer a wider sonic range at lower volume levels. Moreover, RH1060’s earcups are slightly larger and offer a better seal, keeping more outside noise out, and preventing audio leakage, which is a rather noticeable issue with Synchros S400BT.