JBL Synchros S700 Over-Ear Headphone Review

No Noise Cancelling, No Bluetooth, But Something Else Entirely

 The JBL Synchros S700 is one weird headphone. It's got a rechargeable battery and an internal amplifier, but it doesn't have noise canceling or Bluetooth. Why the battery and amp, then? So JBL could implement its LiveSound DSP.

LiveSound DSP is a digital signal processing algorithm that uses crosstalk cancellation and other processing to simulate the sound of ... well, we're not sure. Real speakers in a real room? A live concert? Regardless, the idea is to simulate your body's natural head-related transfer function (HRTF) to get rid of that "sound coming from inside your head" effect most conventional headphones produce.

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No Noise Cancelling. No Bluetooth. But Something Else Entirely.

JBL Synchros S700 headphones


With its stainless-steel headband and cast-aluminum earpieces, the Synchros S700 also sets a new standard in badass looks for a headphone. It's way, way tougher and cooler looking than any headphone currently endorsed by a rock or hip-hop artist.

We tested the Synchros S700 fully in a lab against other headphones for music lovers. Results below.

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JBL Synchros S700 Features and Ergonomics

Closeup of JBL S700 earpiece


• 50 mm drivers
• 4.2 ft/1.3 m detachable cord with iOS/Android-compatible inline mic, play/pause/answer button and volume/track skip buttons
• USB-to-2.5mm charging cord
• Available in onyx (black) or glacier (white)
• Soft carrying case included

Like all of the other active headphones I've tested from Harman brands (including AKG and Harman Kardon), the S700 charges through a USB-to-2.5mm cable, rather than the standard USB-to-micro USB cable most active headphones use. As a frequent traveler, we would hesitate -- strongly hesitate -- to buy or recommend a headphone that uses a non-standard charging cord that can't be readily acquired at Best Buy or Target or RadioShack. 

On my 7-3/4 sized head, the S700 felt a little tight, but the leather earpads distributed the pressure well enough for us to use the headphone for a 90-minute public transit ride without major comfort issues.

To turn on LiveStage, just press on the JBL logo on the left earpiece for a second or so. You'll hear a single beep that means LiveStage is on. Press it again and you'll hear two beeps to indicate you're back in bypass mode. To save battery power, LiveStage automatically shuts off after a few minutes of no signal.

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JBL Synchros S700 Sound Quality

JBL S700 headphones


We first switched on LiveStage while playing Thrasher Dream Trio, which unites drummer Gerry Gibbs, pianist Kenny Barron, and bassist Ron Carter. (Nah, there's no thrash; it's as conservative a jazz record as you'll ever hear.) When we activated LiveStage, we had an instant negative reaction -- that "I hate HRTF processing!" feeling we often get when we've tried similar technologies. Fortunately, we were just about to go grab another cup of coffee -- and by the time we got back to our desk, LiveStage felt completely comfortable and natural.

Without LiveStage, Barron's piano had the spatial properties (although not the tonal properties) of a toy piano stuck inside my head. With LiveStage, it sounded like a full-size grand piano on a stage inside a small jazz club ... a stage inside my head. We know that description sounds weird but the S700 definitely didn't. Gibbs' cuica on "Sunshower" sounded like he was 10 or 12 feet behind the piano, and like its sound was reflecting off the low ceiling of a New York City club.

The only downside we could find of LiveStage (so far) was that it tended (subjectively, at least) to reduce the apparent level of center-mixed sounds relative to more hard-left or hard-right sounds in the mix. This is a common artifact of HRTF processing, and there's an argument to be made that it's a more natural effect than unprocessed headphone sound. Even in vocal-focused recordings like James Taylor's Live at the Beacon Theatre, the slight apparent reduction in the level of Taylor's voice didn't bother us a bit. We just thought we should point it out.

By the way, the S700 still sounds pretty good without LiveStage, but you'll miss LiveStage when it's not there. So if the battery goes dead, not only can you still get sound, you can still enjoy the sound, just not as much.

What we don't like about the S700 may or may not have anything to do with LiveStage. It's the bass, which sounds overly loud and poorly defined. It sounds to me like there's a bump in the response somewhere in the midbass, between about 60 and 100 Hz.

Having heard Carter on a million zillion recordings, and having seen him live a couple of times, we feel we have some idea of how he's supposed to sound, and this ain't it. Carter's articulation is about as good as an upright bass player can get, each note precisely plucked and super-clean. Through the S700 the bottom octave or so of his bass sounded way too full and bottom-heavy. During Carter's solo on "Here Comes Ron," when he went down into the low range it sounded like a totally different instrument, almost like he was trading fours with Jimmy Garrison or Dawn of Midi's Aakaash Israni.

It dawned on us when we were listening to Mötley Crüe’s “Girls Girls Girls” that this bass-heaviness might be a voicing decision to counteract the extra brightness that LiveStage adds. Some people who like lots of bass might really dig it, but much as we loved LiveStage, the bass is just too pumped-up and plumped-out for us to enjoy.

We've seen some negative comments about LiveStage out there, Of course, everyone's entitled to their opinion, especially when it comes to headphones. And as we noted in this blog, it's only natural for people to react differently to the same HRTF processing algorithm. But after reading some of these comments we have to wonder if:

A) The writer rejected it simply because it's not the headphone sound he's used to
B) The writer grasped what Harman's engineers were trying to accomplish
C) The writer had any previous experience with HRTF processing. (We do. We've reviewed several HRTF processors dating back to the Virtual Listening Systems processor in 1997)

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JBL Synchros S700 Measurements

Graph of results


You can see our full lab measurements for the S700 in a photo essay. The graph above is the most important. It shows the response with LiveStage off (red trace) and on (purple trace). You can see fairly mild shifts in tonal balance when LiveStage is activated, plus some of the artifacts of the DSP algorithm. Nothing to be concerned about, but it does give you some idea of what LiveStage is actually doing.

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JBL Synchros S700: Final Take

JBL Synchros S700 headphones


In a lot of ways, the S700 is a really nice headphone. World-beating build quality. Friendly ergonomics and fit. Cool styling. But the bass needs to be tamed and tightened, and Harman should add a standard micro USB charging port.