JBL Synchros S400BT review

Incredible sound and design knocked down by connectivity issues

JBL Synchros S400BT review

TechRadar Verdict

With cheaper wireless alternatives available, the S400BT doesn't put forth the winning argument it needs to justify a higher price.


  • +

    Magnificent design and sound

  • +

    Long battery-life

  • +



  • -

    Spotty Bluetooth signal strength

  • -

    Price is a bit high

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Stripped down of all its niceties, the JBL Synchros S400BT are a great set of headphones. The sound is full and it hits all the marks no matter what kind of music you toss at it. Comfort was never an issue and the battery life seemed to last longer than it should have. I could go on, and I will later in this review.

Once you add in the fine details, along with features like touch control and NFC tap-to-connect functionality, the S400BT seems like the wireless headphones you’ve been waiting for all along. But at $229 (£199, about AU$279), is the package convincing enough to choose over JBL’s own $99 wireless E40BT, or other competitively priced wireless headphones?


A glance at the JBL Synchros S400BT shows that JBL likes to blaze its own path. Matte-coating, glossy and cross-hatched plastic here, stainless steel and leather there. It’s a beautiful mess of materials that somehow comes together well.

JBL Synchros S400BT review

There is a method to JBL’s madness, however, as the S400BT’s design yields durability and comfort. The elegant stainless steel headband, which adjusts large enough to fit my head (larger than most, I’d say), is seamlessly fitted on its underside with a thick bit of leather cushion to rest softly on your head.

The thick, matte-coated arms on the left and right act as the site of flexible articulation for each of the earcups. The S400BT may look stiffly professional, but I was able to fold, bend and compact them to fit a coat pocket in a pinch, something the crowd who digs sporty, ultra-portable headphones will enjoy.

Earcups are the undisputed heart and soul of headphones. The ones in the JBL S400BT have the heart and soul, but they also have brains. Inside the soft, leather-coated on-ear cups, which have a small, but serviceable range of motion, are 40mm drivers.

Additionally, there’s a rechargeable battery inside the left earcup promising up to 15 hours of battery life. It’s where you’ll also find a 2.5mm input that offers dual functionality by way of charging the headphones, as well as offering up the option to use them as wired headphones if you can’t reach a USB port and the battery depletes.

JBL Synchros S400BT review

Here’s where things get brainy. Since we live in the future and there’s somehow still room inside a kid fist-sized earcup, you’ll find all the controls here. Along with standard fare like a power and Bluetooth connect button, several touch gestures are built into the glossy face of the earcup. The right earcup hosts the NFC tap-to-connect site.

Based on looks, the JBL Synchros S400BT tries its best to justify a premium price and does a good job of it. But does the performance tie a bow around the package or cover it in mud?


When it comes to headphones, performance begins and ends with comfort, and comfort of on-ear headphones is often hit-or-miss with me. These brilliantly walk the delicate line of squeezing against my ears just tight enough to minimize sound leakage and remaining breathable.

Sound performance is good, though a bit of the richness and bass escapes with a turn of the head, which usually causes the seal between the cup and your ear to break.

Gesture controls work as expected. Tap once to pause music or take a call. Swipe up or down to adjust volume. Swipe left or right to change songs. Of all the premium features included, this felt the most tacked on and uninspired. It’s a neat feature that might seem desirable to some, but if it had meant the difference of $50 or more for the S400BT, I would have left it on the curb.

JBL Synchros S400BT review

The rechargeable battery worked like a champ, often providing me with just over the advertised 15-hour battery life. Though its roots are in wireless, JBL didn’t forget the 2.5mm to 3.5mm cable, which I was pleased to resort to after a long flight drained the headphones.

Unfortunately, Bluetooth signal strength was an issue for me. Connecting is a breeze, but I consistently encountered connectivity issues with the S400BT. Not only does it require absolute line-of-sight with the device it’s connected to, a simple turn of the head can stop the flow of audio completely.

Wireless came with an asterisk in the case of the S400BT, as I usually had to have my phone in a breast pocket to get a clear signal. It pains me, as these headphones do so much right, that they can’t get the fundamentals down.

We liked

The look and feel of the JBL Synchros S400BT won me over quickly. I’m a sucker for the clean, professional presentation and JBL made the offering even sweeter with the solid battery-life and powerful sound drivers. I also liked the clever 2.5mm to USB charging method.

We disliked

Not much, that is, until it came to Bluetooth performance. Mimes will love it, as it rewards the motionless. Unfortunately, that subjects about 99% of the population to shoddy signal issues.

Final verdict

It’s 2015 and wireless headphones are cheaper than ever. Some at retail are going as low as $100. So just what does the JBL Synchros S400BT do differently to justify its $229 price tag? Not enough.

If it’s wireless or bust, stick with the $99 JBL Synchros E40BT, an option that has most of the functionality of the S400BT at less than half the price.

Cameron Faulkner

Cameron is a writer at The Verge, focused on reviews, deals coverage, and news. He wrote for magazines and websites such as The Verge, TechRadar, Practical Photoshop, Polygon, Eater and Al Bawaba.