Sennheiser 4.40BT Review & issues!

The Bluetooth headphone market is dominated by Bose and Sony, but Sennheiser has entered in the game at the $150 price point with their HD 4.40BT wireless headphones, and the result is actually good, but not without some issues.


Sennheiser is known for their well thought out design and material choices, and at least the material  choice part is true for this headphone. Even though the headband isn’t very wide, the combination of plastic and silicon is executed in a way that makes it feel reassuringly strong.

The part of headband that extends out for size adjustment also feels strong, even though it may look like a thin piece of plastic. The hinges for both the vertical and horizontal rotation also feel strong, and there’s no squeaking noises at all. The two step folding mechanism is also great and allows for any one of the ear cup to be on top, so you don’t have worry about which one will go first.

The earcups are thick and have memory foam inside, and while they are very soft, comfort is a complicated matter with these headphones, which we will talk about later in this video.

I really like the design of this headphone, it looks very modern, and the branding and color choice is very tasteful. It has a very sleek and minimalistic look, there’s a subdued Sennheiser wordmark on the headband, and the logo on both sides on the earcup hinges.

Inside the box, you will find a carrying pouch which offers minimal protection, then you’ll find operation manual which you should read, then the wired cable for these headphones, a micro-USB cable for charging, and finally the headphones folded inside.


The headphone is light at 225 grams, but because the headband isn’t wide, you do feel the weight on a small area of your head, which isn’t comfortable.

The earpads are made of very good materials, they are thick, and have memory foam inside, so they are very soft too. But the biggest problem with these headphones is that the earpads have very small opening. Even though I read in online reviews that this would be a problem I thought they were over exaggerating it.

I have slightly bigger than average ears at 7.5 cm, while the world average is around 6.5 cm, so I think people with small to average ears won’t find this uncomfortable, but for people with larger ears, this can be a big problem.

The clamping force isn’t very high, but because the earpads are uncomfortable, it starts getting painful after sometime for me. You can find the right position with some fiddling, and then it can be comfortable enough to wear for an hour, but saying that your mileage may vary will be an understatement, and you’ll have to try them on to know for sure.

I thought that the M50x were uncomfortable, but these are even more uncomfortable, and I cannot wear them with glasses for even half an hour, they also get hot very quickly so if you seat a lot this could become a big problem.

One fix that makes a big difference is removing the earpads , and then fit them on again upside down (watch the video for the process). The problem with these earpads is that these have these 4 stitching lines at the bottom of the earpad, and it becomes very uncomfortable when these sharp and hard stitching lines press against your earlobes, so when you turn these upside down, this part goes to the upper part of the earpads, and they become much more comfortable, and the stitching lines don’t hurt the upper part of the ear.

You can also add more padding to the headband, which in addition to making them more comfortable on your head, also reduces the clamping force.

These were still not comfortable enough for me to wear for an hour, so to fix this I bought the Brainwavz HM5 velour earpads, which are much larger than these, and even though they didn’t work well with my M50x, I thought that because these have the drivers at a distance from ears, like the HM5 headphones, they should work better with these.

The opening for the earpads on this headphone is VERY narrow, so fitting the HM5 pads was very difficult. But the sound changed too much with these, below an acceptable level. The bass almost became absent and the highs became sibilant and harsh, so these very popular earpads won’t work with these too, simply because there’s a BIG difference between the size of the earcups.

So the comfort is really a mixed bag with these, if these fit you well, you’ll find them to be comfortable for hours, but if they don’t, then even half an hour could be difficult, and you may have to spend some time it getting these positioned right. If you can find an earpad replacement, that is comfortable and doesn’t destroy the sound quality, all these problems can be fixed.


This is a Bluetooth headphone with aptX, so it should have higher quality output than the non-aptX ones with compatible devices. Range is great, and I can move around in my flat without dropping  the connection. All the controls and ports are on the right ear cup, where you will see a status LED followed by the power button, the multifunction slider button, the volume adjustment buttons, then a 2.5mm input jack for wired connection, and then finally a micro USB charging port.

The controls are unfortunately not easy to operate, because they are small and feel almost the same. I really dislike how the multifunction slider button works, especially because the basic functionality of play/pause is achieved by pressing the multi-function button inside. Now the problem with that is that it’s not actually a button, but it feels like the trigger buttons on an xbox controller, meaning that it doesn’t click when you press it, but it goes inside with resistance but without any feedback, and because it’s a slider, it can slide if you press it at the wrong angle, which makes this inconvenient to use. And you will have to press or press AND hold this button for 2 seconds to play/pause, to attend and reject calls, to put them on hold, and to voice dial or use voice assistant, so the fact that the most used button is the most inconvenient to use here is a BIG let-down, and I really wish that they didn’t use this slider mechanism for so many important functions.

It will also take a few days to get familiar with the positioning, the differences between the feel of buttons, and how to press them correctly. It’s not actually as bad as it may sound with all the details, but it’s definitely not a very good implementation.

The power and volume buttons are thankfully easier to use and have some feedback.

With the 2.5mm jack, you can use this like a wired headphone with the supplied cable. Even though Bluetooth doesn’t work while the cable is connected, I think that it’s a good thing because it skips the electronics and if the electronics inside stop working correctly, you should be able to use this as a wired headphone. The sound quality in wired mode with a dedicated DAC AMP only gets a slight improvement, which means that Sennheiser has put good quality components inside and there’s very little compromise on sound in wireless mode.

It has a battery life of around 25 hours, which is really good, and it charges quickly in two hours. I think most people will only have to charge it once or twice a week.

The earcups are small, but it has to be considered that these headphones area designed to be more portable and isolating than other headphones which you might use at home, so the small earpad opening, coupled with their thickness and tight seal make these headphone very noise isolating, and even though they do not have Noise Cancelling functionality, the isolation they have is good enough to make them usable in a gym or in an airplane.

It has 2 microphones, and the quality in calls is really good. One great feature on these is that while in calls, you can also hear your own voice while talking, which is really great because these headphones are so isolating, that they will also block your own voice which might make you speak louder.

On the left earcup, there’s only the NFC transmitter, and the great thing about it is that even if you have the headphones turned off, and you bring your phone close to it, it will power on and connect to the phone, so that’s very convenient.


Now coming on to the sound quality, I have to say that these sound better than I was expecting for a wireless headphone. When I talk about the sound quality, it has to be considered that this is a wireless headphone, which in addition to the drivers, has to have a Bluetooth receiver, a DAC, an AMP, and a battery built into it.

Starting with the Bass, these are definitely have emphasized bass. It’s not overpowering, and does bleed the midrange, but it definitely sounds like leaning towards the bassy side of the spectrum. You can hear the sub bass clearly in tracks that have sub bass, which is generally not very prominent in the neutral headphones, and it can be enjoyable in bass centric music. It makes these headphones really great for electronic music.

The bass is adequately fast, so it’s not exceptionally tight or loose, but it is actually better than what I was expecting. Now I don’t know what bassheads like, but any more bass in these headphones would only make them worse, so as far as bass heavy headphones go, for me, this is as far as they should go.

Now coming on to the mids, they are not great, but they are good enough to not keep you from enjoying your music. One problem with the mids is that they have a bump in the 1kHz point in the frequency range, which means that your audio in this part is going to sound louder than other parts of the audio. Now this part has the upper range of the voices, so a bump here makes the voices sound a little artificial in the music. This is not a big problem, but once you notice it, you’ll definitely keep noticing it. In movies it is actually good and makes the dialogues more audible, and in electronic music that has subdued vocals, these headphones will bring them out, which can be enjoyable. But in all other types of music, the vocals are going to sound a little artificial and radio like.

Thankfully it is very easy to fix with an equalizer, and once you turn down the 1kHz slider by almost 3 decibels, voices and vocals will sound very natural, and this issue is completely fixed.

Now the high frequency range of these headphones is what I found to be a little disappointing. Sennheiser is known for rolling off the highs a little, and I generally like the Sennheiser sound signature, but on these headphones, I think that the highs are the biggest weakness. The highs lack the presence and sparkle, so if you enjoy the liveliness that good highs provide on a headphone, you are going to miss it. This also means that classical music is not going to be very enjoyable on these headphones.

The highs can be improved by turning up the equalizer slider at 14 and 16kHz by 2 or 3 decibels, It helps with the lack of presence in the highs and makes these headphones sound more balanced.

Now all of this might sound bad, but it’s not that bad considering that this is a wireless headphone, and it is a little unfair to compare it with the wired headphones in the same price range. But all of this is to just give you an idea of how they are going to sound.


The soundstage on these headphones is good for closed back headphones, but it has some odd characteristics because of the uneven frequency response.

The audio in the low and mid frequencies has good separation, but because of the lack of the presence in the highs, the instrument separation in the mid to high frequency range isn’t great.

So for example, in Hotel California [mention by Eagles], the bass guitar and vocals have good imaging, but the high notes on rhythm guitar, and the high hats of the drums don’t have good separation, and they feel like they are condensed into a small area. Using the equalizer makes the soundstage better by some extent.


So in conclusion, I think that these headphones are good entry by Sennheiser in this price range, they sound great and relatively balanced for a Bluetooth headphone in this price range, and as long as you don’t have large ears, you are going to find them comfortable enough.

For people with larger ears like me, I have mixed feeling for these. Comfort is a very important factor when it comes to headphones, so in case they don’t fit you well, you will have to find an earpad replacement which has a similar design. There are other options like Sony XB950BT available, but I don’t like bass heavy headphones, and I read too many reports of them breaking in less than a year, so I don’t think that they would have been a better choice for me. So in spite of all the issues that this headphone has, I’d still go for it, in this price range, for a wireless headphone.

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