If there's one thing I've learned over the years, it's that most people like bass, and they like more bass even more. I suppose JBL engineers know the same thing, and they made sure the new Synchros S700 over-the ear, closed-back headphones deliver incredibly deep bass.
Designwise, JBL avoided the slick, plastic look of Beats and other fashion-oriented 'phones. The Synchros S700's precision die-cast aluminum earcups look like they mean business, and the headband is steel-reinforced, so the headphones feel really solid. One other reason for that is the headband isn't hinged, so while it can't fold for compact storage it will probably outlive most hinged designs. The earcups turn to flatten out, so the Synchros S700 can be safely stored in the included carrying case. For me, head-clamping pressure was fairly high, and that negatively affected comfort after an hour of playing time. That said, I find most headphones' fit relaxes a bit as the months go by, so the Synchros S700s will probably get a little more comfy over time.
The headphones have large 50mm drivers; most competing designs rely on 40mm drivers. The headphone features JBL's proprietary LiveStage digital signal processing technology that's supposed to get the sound out of your head, and make a sound that's more like speakers in a room. That's the promise of the Synchros S700's "advanced, binaural digital signal processing," but the reality is just a slightly more open soundstage. I found LiveStage most effective with sparsely mixed recordings, but with more densely mixed music LiveStage just changed the sound, and sometimes thinned out the bass. A button on the left ear cup turns the processing on and off, so it's easy enough to try the LiveStage effect on different tunes. The electronics are powered by a built-in lithium ion battery that can deliver up to 28 hours of listening time. Once the battery is drained you can continue to listen without LiveStage. Battery charging is accomplished with the included USB cable. JBL claims that the Synchros S700's mic and three-button control are compatible with iOS or Android devices.
On tunes with just a few instruments LiveStage broadened the soundstage, and turning off the processing was a letdown. On more densely mixed tunes LiveStage just brightened the treble and widened the imaging stage. I didn't always like it, but sometimes it really helped the sound.
I next compared the Synchros S700 with Beats Pro headphones, which are no slouch in the bass department. Nine Inch Nails' "Hesitation Marks" album is loaded with superdeep bass, and both 'phones plumbed the depths, but the Synchros S700 went deeper. There was more impact and power down there on the Synchros S700; moving up to the midrange and treble I found the Beats Pro more natural. Without any processing the 'Pro also produced a bigger/wider soundstage than the Synchros S700. Turning LiveStage on put the Synchros S700 slightly ahead of the Beats Pro, producing a big, spacious sound on Daft Punk's "Lose Yourself to Dance."
Continuing with acoustic music the Beats Pro was more natural-sounding; it was a better, more evenly balanced sounding design than that of the Synchros S700. There's no decisive winner in this contest, and neither headphones will hold much appeal to audiophiles or anyone seeking accurate sound. For them I still recommend the Hifiman HE-400 or Sennheiser Momentum over-the-ear headphones in this price class.
The JBL Synchros S700 will be available for $349 in early December.