Product Review: JBL Synchros E40BT Bluetooth Headphones

Electronics GeekMom
The JBL Synchros over-ear Bluetooth headphones are super-comfy for all-day-at-your-desk wear. Photo: Patricia Vollmer.
The JBL Synchros over-ear Bluetooth headphones are super-comfy for all-day-at-your-desk wear. Photo: Patricia Vollmer.

Along with the JBL earbuds I had the chance to try out earlier this month, I had received some more substantial over-ear headphones to review. I elected to review these separately because I wanted to open up my options for trying them out; I used them at my office for about a month.

The JBL Synchros E40BTs are over-ear wireless Bluetooth headphones. I loved the idea of these high-quality headphones being wireless. So I decided to give these a chance at my new office to see if they would play for me ALL DAY. Read on to learn more about these headphones.

What Comes in the Box

The E40BT headphones include a charging cable along with a custom auxilliary cable so the headphones will work even when there isn't enough battery life for the wireless Bluetooth version. Photo: Patricia Vollmer.
Unlike the other Bluetooth headphones I’ve reviewed, this set includes a connection cable so that you can still use them as wired headphones. Photo: Patricia Vollmer.
  • E40BT Synchros headphones
  • Instruction booklet
  • USB charging cable
  • Auxiliary-style  cable to use the headphones even after the battery dies


Very little setup is required. My headphones arrived partially charged, so I was able to make the Bluetooth discoveries with my devices right away. I enjoyed several hours of listening before they needed a charge.

Bluetooth setup is controlled with the power switch, and the instruction booklet provides instructions for pairing with your smartphone, tablet, or computer. I had no problems with Bluetooth discovery.

Fit and Comfort

I find these headphones very comfortable in not-too-warm temperatures. Unlike other full-sized studio headphones I’ve reviewed, I never felt the weight of the headphones even after several hours of listening. The ear cups and headband have leatherette-covered padding, which makes for a comfortable fit, but I’d be wary of how the leatherette will feel if it’s really warm. It’s not a porous material and might not be very comfortable on the ears if you’re sweaty.

The headband is adjustable, and I found a size to fit me very well. I have a larger-than-average head, but I was surprised that the best fit for me is the maximum size. I didn’t think my head was that big.

I wore these headphones up to four hours straight while working at my desk and didn’t have problems with comfort or fit.

The earcups pivot for an even more comfortable fit, and can pivot inwards 90-degrees for nearly-flat storage.


All the controls for the E40BTs are on the left earcup. This is convenient, but I will explain some design concerns I have with the power switch.

Once you have music playing, you can use the side panel to control volume and the play/pause/fast forward features. The circle-icon next to the “J” in “JBL” is a multi-function switch that can pause, play, and control the fast forward and rewind of tracks. You have to hit that button up to three times in succession to get the function you desire, and I found this cumbersome. If you don’t hit the button three times with the correct spacing between the taps, you don’t get the desired rewind.

You can also use these headphones for phone calls when paired with a smartphone. The control buttons work similarly; use the multifunction switch to accept and hang up phone calls.

All the controls, from the on/off switch, to the music controls, are on the left earcup. Photo: Patricia Vollmer.

The power button is the rectangular button with the Bluetooth logo on it. It doubles as the Bluetooth control button. Follow the instructions to have your devices discover and pair with the headphones. I was able to have this work with my iPhone 5S, MacBook Pro, and Samsung Galaxy Note tablet.

I do not like the placement of the power/Bluetooth button. When putting on and taking off these headphones, my left thumb naturally wants to be right on that button, and I have inadvertently turned off my headphones dozens of times in the weeks I’ve been using these headphones at work. I think this button would be better on the bottom of the earcup instead of on one side or the other.

If you don’t want to use the Bluetooth feature (such as with a dead battery), you can connect the wired cable with the headphones. The 2mm port is located at the bottom edge of the left earcup. Be careful not to lose this cable! You cannot simply buy a generic auxiliary cable to serve this purpose, but if you can find a 2mm to 3.5mm cable, it might work as a replacement. You could also invest in an adapter if you need to replace the cable with a 3.5mm to 3.5mm aux.

It takes about 3 hours to fully charge the headphones with the included USB cable. It conveniently fits into the same 2mm port that the auxiliary cable uses. From this charge, expect up to 16 hours of listening (which I easily got from my charges), and up to 25 hours of telephone talk time (which I cannot vouch for, since I haven’t talked that much on my phone).

I really liked not having my headphones yank me back to my seat when in my office, which I’ve experienced many times with wired headphones. I could wear them for several hours in my office while working on lesson planning and checking emails.

Sound Quality

While these aren’t advertised as “noise canceling,” they do have a small amount sound insulation since the ear cups completely cover your ears. I found the sound quality very good; I mostly listened to numerous channels with my office computer while working at my desk, with channels ranging from “Cake” to “311” to “Mahler.” I also used them to listen to online training modules and a couple of YouTube videos. Usually I had to ensure the volume was low enough so I could hear if someone was at my office door, but if I wanted to make it louder, I could get the headphones to play pretty loudly without compromising the treble or bass qualities of the music.

JBL advertises something called “PureBass Performance” which is a proprietary feature advertising “high-performance drivers,” “outstanding frequency response,” and “pure bass which is deep, powerful, and accurate.” I’m not super-sensitive to whether these qualities are accurately described, but it certainly felt to me as though these features were there, especially with Mahler’s 1st Symphony.

I’ve no complaints about the E40BT’s sound quality.


The “ShareMe” feature is unique to JBL’s higher-quality headphones. It can allow two or more users with JBL’s ShareMe-featured headphones to stream music directly from one set of headphones to the others. The control button on the left earpiece with with “play arrow” is what can control this.

I was unable to test this feature: I only received one pair of E40BTs, and I know no one else with these headphones.


With the exception of the placement of the power/Bluetooth button, and the multifunction button being a bit complicated, I thoroughly enjoyed these headphones in an office or commuter environment. These are not for exercising (the JBL Synchros earbuds I recently reviewed are more appropriate for high-impact activities).

JBL E40BT headphones come in a variety of colors, and is available at retailers such as Amazon for an MSRP of $99.99.

GeekMom received this product for review purposes.

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25 thoughts on “Product Review: JBL Synchros E40BT Bluetooth Headphones

  1. I can’t workout how to charge mr Jbl E40BT headphones. I plugged in the charging cable and plugged it into both a laptop and an adaptor that you can plug the USB cable into. I’m not sure whether to leave it on or off when charging it and I don’t know of it’s charging or not. The red light just keeps on flashing. Help is needed please

    1. I’m from the Philippines and our electric outlet voltage is 220. If I plug the charger on my wall, will the headphone tolerate it? Do I need to get a transformer to bring down my electric voltage to 110 volts?

  2. Excellent review, I’ve buyed these headphones through Amazon, in few days I can test those features by myself 🙂

  3. Thanks for the review. I recently purchased a set of JBL J88 full size headphones that broke on me, JBL is replacing them with a set of these E40BT’s ” which i’m eagerly awaiting “. It’s nice to read reviews from everyday people, not just those paid to review items. Take care 🙂

  4. You can get them at your local sorint store/ radio shack for the same price without the in the mail wait time.

  5. How do you turn these headphones off? I’ve just been disconnecting the Bluetooth but the headphones stay on. I don’t want to have to continuously charge it every day.

    1. As stated in the manual, you press the Bluetooth button down for nearly a second. You should get a small sound.

  6. How do you know when the headphones are done charging? Does the Bluetooth emblem charge colors or something like that?

  7. If you connect the headphones without blutooth (with the cable) does the mic work? Pls reply

  8. Mine didn’t come with an auxiliary cables so now I have to wait for my headphones to charge when I want to listen to music. It fucking sucks.

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