OVERVIEW: I've been in the market for wireless earbuds for about a year now. I can't stand the hard plastic Apple air pods. Frankly, I don't know how anyone can. The hard shiny plastic is not ergonomic and does nothing to hold them in my ear, and they leak sound both in and out like sieve. Anyway, that's neither here nor there. Enter the Sennheiser CX400BTs. A brand I'm more than familiar with and one that I trust for both build and sound quality and they mostly do not disappoint.SOUND QUALITY 5/5: Overall these score very high, as they should for being Sennheisers. The soundstage is pretty wide considering these are earbuds. The music doesn't feel like it's on top of you. It has a surprisingly good amount of room to breathe. This makes the imaging very good as well. Imaging is when you can hear the instruments and other acoustic sounds as if they were behind, beside, above, and even in front of you. Think anything by Pink Floyd with all the different sound effects in the background. EQ is hard to rate, really, because the EQ is customizable on the Sennheiser Smart Control app where you can adjust the levels to your taste. This is probably my favorite feature about these earbuds. Having the control and freedom to tailor the sound to how YOU want it is liberating. You're not stuck with whatever the manufacturer thinks sounds good. You can increase bass if you're listening to ambient/electronica or you can boost mids and decrease the highs if you're listening to podcasts. So in all, the sound quality is excellent, but it all depends on how you set it up. Additionally, you can save these custom sound profiles as a preset so if you don't have to fiddle with them every time you switch genres. This feature is simple and intuitive and is extremely useful. While these do not have active noise cancellation, the silicone tips do more than a good enough job isolating the ambient noise around me, allowing me to be immersed in my music. Personally I don't like ACN anyway. I don't like the feeling of pressure they create so this is a non-issue for me.CONSTRUCTION 5/5: These have the typical high standard of build quality that I expect from Sennheiser. Nothing feels cheap or chincy. All the plastics feel thick and sturdy. The case is small, compact, and is sleek in design. It doesn't have the fabric case that the Momentums have and some people complained about that but you have to remember, they're $100 cheaper, and this decision was purposeful. It seems Sennheiser cut out the more luxurious things in order to bring the price down to a more affordable level, but left alone the important things like sound and build quality. They share the same 7mm drivers as the Momentums, and this is where they really shine. If you're letting the carrying case stop you from buying these, that's your problem.ERGONOMICS 4/5: These fit in my ear nicely and are lightweight enough to not feel in my ear. They come with three other sizes of silicone tips so they should be able to fit most people's ears with no problem. That being said, they aren't small. They do protrude a bit from the side of my head. They're not exactly inconspicuous in design but personally I don't care what others think. I bought these for the sound quality, fit, and ease of use, of which these excel. I can wear these for long listening sessions without experiencing pain or discomfort in my ear canals.TOUCH & BLUETOOTH 4/5: The touch commands are easy to remember and simple to use. I won't go over them here. Just know they're not complicated. But if you happen to not like the touch commands, you can customize them to be whatever you want on the app. Yet another feature that Sennheiser includes to make these more versatile and user friendly, especially if you're used to a certain touch command form another brand. Sennheiser flattens out the learning curve with the flexibility of making this customizable. Pairing is easy to do. Simply touch both buds while in pairing mode until it pairs and viola. No need to keep pairing every time you listen to them. Just on the initial setup and then they connect automatically when you insert them in your ear from then on. The only bad thing I can say about hte touch controls is the slight lag time processing the function. There's about a one second delay in pausing/playing, skipping songs. It's a very minor irritantPHONE CALLS 5/5: I tested out the phone function and I could be heard clearly on these headphones with very minimal, if any lag.OVERALL: I really like these and I'm really glad Sennheiser finally released a more affordable set of true wireless earbuds that didn't sacrifice sound or build quality. Not everyone can afford the Momentums and these are a solid alternative. The freedom I have by ditching the wire is huge. No more snagging it on things as I walk and ripping them out of my ear. No more stupid lightning adapters to make headphones work with my iphone. These are very convenient in that regard. I love the way they sound and how easy they are to use.PROS & CONS:PROS:- Excellent sound quality- Excellent build quality- Intuitive, simple to use Smart Control App allows you to customize sound levels and save presets, and allows you to customize touch commands- Lightweight- Doesn't cause ear fatigue/discomfort- Simple, easy to remember touch commands- Charging case takes USB-C- Phone calls have almost no lag- NO WIRES OR ADAPTERS!!CONS:- Battery life is not nearly as long as they claim (20 hours). I get around 5-6 hours. More in the update below- Be aware that if you place an earbud down on a metal surface, the magnet will read it as you touching the control for volume and it will increase or decrease the volume depending on which one you take out and put down. It’s a little annoying but I understand not too many people work around metal surfaces as much as I do so it’s more of a problem for me, specifically.- Protrudes from ears a bit and makes them less discreet than other brands- No ANC, but this is subjective. Not a problem for me but may be a deal breaker for othersUPDATE: I’ve owned these for quite a while now and while most of my above review still hold true, one annoyance I keep running into is battery life of the buds. These don’t last nearly as long as they claim. They claim to last 20 hours on a full charge. I estimate last about a quarter of that. I’ll listen to these a couple hours a day max. I will put them in on the third day after a full charge and the left one will die within a few minutes while the right one still works. I’ll check the charge and it’ll say 20%, meaning the right bud. It’s always the left that dies first and you can’t see the charge for both individual buds. It appears to give you the highest charge between the two, which is useless because if one dies, who cares how charged the other one is. No one wants to listen to music with one bud. I wish there’s had a low battery warning. Just a subtle yet noticeable tone to let you know you need to charge them soon. Unfortunately you just need to keep checking the battery percentage manually from time to time. Sennheiser needs to implement a way to check the charge of both individual buds and they also need to implement a low battery warning so we aren’t in the middle of listening when the left one suddenly cuts out. Because then you can’t listen to music for a couple hours while they charge. For these reasons, I have to give these 4 stars instead of 5. Battery life and ease of use is important with wireless buds. If they lack these things, it makes for an unenjoyable experience.Let's get the obvious out of the way: these buds are larger than you expect, and heavier, in part due to the 7mm driver (same as the more expensive Momentum line from Sennheiser)... but you won't care about the size or weight, because they just sound so, so incredible.That 7mm driver does make amazing sound, better than any wireless earbud I've tried, and for around $100 at the time of my purchase, this has better "quality sound / dollar" than anything I've tried.But there are some odd design decisions. The touch surface for the control on the outside of the big block is hypersensitive (even a quick touch from my hand can trigger a pause, much more sensitive than, say, Airpods Pro). On the good side, you can control volume from these, but it's a bit tricky due to the sensitivity. For all the audio quality, I found I had to set the volume higher with these than with other earbuds on both iPhone and Windows PC Bluetooth (in Windows, go to Sound in the Control Panel (under "Hardware and Sound"), highlight your headphones, click Properties, and select the Enhancements tab. Check "Loudness Equalization" and hit Apply to turn this on, helps a ton). With the plugs in, your do get good isolation from the outside (so "passive" noise reduction), though of course, you now hear every breath and gurgle from inside your body, as you do with any sealed-ear device. Even with a Bluetooth 5.0 connection (they support up to 5.1) on the PC, BT lag is still present; this is really evident watching videos and, to some extent, on video conferences. The buds stick out from your head, and are heavy, so extended wearing became ear-canal sore, but never really painful. The ear tips are silicone, but less flexible than from other vendors: I usually wear a medium in other earbuds, but it feels a touch large for my ears; the small felt too small. I may invest in Comply Foam for the first time.The buds support SBC, AAC and aptX, which is nice for iOS or Android users. Microphone quality is the usual: it's good enough, but not as good as Airpods Pro, and clearly not the primary focus of the buds. It'll be ok, but expect to have to repeat sometimes, as with almost every wireless earbud out there. Also, I missed the auto-shutoff from so many of the other modern earbuds; these just keep playing when you take them out (luckily, due to the hypersensitive touch panels, I accidentally pause when taking them out most times!).Also, an odd design choice means that the "power pads" where the buds connect to the terminals in the case is just rear of the earplug; this puts a ridged surface directly touching one of the folds of the ear. If you push the earpiece all the way in, you are putting the one rough surface directly against your ear. Sennheiser could have easily put this on, say, the rear-facing portion of the block and let smooth plastic touch the ear, but, well, they didn't. You'll get used to it, but it's just an unnecessary design choice.Connection is quick with verbal feedback in the buds. Battery life is as expected, and runs easily the 6 or so hours; the case can give another 12-13. It takes longer than an Airpod Pro to recharge; it's worth charging over a longer break than just the few minutes other products can charge in. The case has a USB-C plug, but the included cable is tiny; throw a normal length one in your cart when you buy this. The case has no wireless charging ability, oh well. The case is larger than expected, a little heavier than an Airpods Pro case, and due to it's rectangular shape and width, a bit pocket un-friendly. The top does have a hinge-helper which holds the top open, something more cases should try.Sennheiser has an app for iOS and Android, and it really is necessary. It allows a firmware update to 2.13.0 that substantially improved connection speed. You can customize almost all the tap patterns; I added "play pause" to the right ear instead of just on the left. It also lets you store different EQ profiles (just 3 bands, so a bit gross, but better than nothing; there's also a "touch and slide" interface but it's really just a layer on the 3 band). The profiles are stored in the bud, and can be changed live via the app, even if you are listening to another source (so, using the phone to adjust the eq while listening to the computer). The app lets you control the connections as well; like most BT devices, you can't connect to more than 1 source hot at a time (aka no multipoint), and switching is still manual (Apple's Airpods ecosystem is more automatic, and Bose has done a nice job of having 2 sources mounted at once and having easy swapping between them).These are not sport buds: they don't quite stay in all that well (in my ears) when moving and have 0 water/sweat protection beyond the usual (a bit will probably be fine, but during a heavy workout, these re not fully protected from salty sweat.)So, other than odd choices in where to put the power connectors, the large size of the main block, the sensitivity of the touch panel, and oddities of the eartips size, the sound quality is amazing, far better than I expected from a Bluetooth connection, esp. for the price. Master and Dynamic has a similar pair that drop in price to around $100, and Yamaha has a nice pair around this price with similar specs, but after trying them all, I'm willing to put up with the odd design choices for that clean Sennheiser sound.The review for:"Sennheiser CX400BT True Wireless Earbuds".Ships from and sold by Amazon.ca.Overall: 5/5Sound quality: 6/5Bass quality: 3/5Functional feature: 4/5Bluetooth connection: 3/5Fit in ear: 4/5Battery life: 3/5Passive noise cancellation: 4/5Active noise cancellation: n/aTransparent hearing: n/aBudget friendly: 5/5Mono/Independent mode: n/aStatic noise: barely noticeableWaterproof: --Delivery: 6 daysPurchased time: Jan 2021Scale5=best 6=superior4=good3=decent2=poor1=better than nothing0=better without itn/a=nonesp=depends on individuals or situations--=haven't test, measure, nor paying attentionOverall: 4/5Very good pair, GREAT sound signature and quality. A budget deal for great music earbuds, just like the "Momentum TWS 2". The misleading(my case) playtime description is also just like the "Momentum TWS 2" as well. The lacking of ANC and transparent mode might massively affect outdoor users.Pros: GREAT sound signature&quality(TWS), customizable touch control, budget friendly to music listeners using TWS.Cons: 4hrs battery, no IPX rating, no transparent mode.Sound quality: 6/5Superior sound quality compare to almost all other true wireless earbuds. Very pleased sound signature that stands out from all other true wireless earbuds. It is not the best sound quality EARPHONES, but I doubt there is any TRUE WIRELESS EARBUDS with a better sound quality than this one.(Only heard the momentum 1&2 TWS might have better sound quality.)Bass quality: 3/5There is decent bass, just not for bass-head.Functional feature: 4/5Have all necessary features for indoor music listening. Customizable control feature could be very enjoyable for using experience.Bluetooth connection: 3/5Decent, not strong compare to others. Only used for music listening, not tested for lagging. Short pauses occasionally happens while playing l, last 0.3-1s each time.Fit in ear: 4/5Comfort in general. Decent secure fit. The size of the buds itself could be a little big, no issue for long time wearing, not recommended for activities with head movements. A little slippery when holding with fingers on the earbuds, much better than the "Momentum TWS 2" on hand due to its square shape.Battery life: 3/5Decent but disappointed. Unlike its advertised 7hrs for playtime (50% volume), the playtime I tested barely passed 4hrs, could gain another 40mins when just listen to audiobooks. It could be a lemon, or 3, make it 5 if add the "Momentum TWS 2" experience to the list. The white colour I tried got me another 15mins compare to the 2 black colour I've tried.PS: The battery of the case could fully charge the both buds for at least twice for extension.Passive noise cancellation: 4/5Good seal. When wearing both ears, may hard to identify the contents of speaking.Budget friendly: 5/5Considering to the similar sound quality with Momentum 2 TWS, the current price is very budget friendly for music listeners who like to have a pair of quality true wireless earbuds.Purchased price: CDN$ 129.95Review posted: Feb 2021Tengo otras marcas de audífonos true wireless como Amps Air 2.0, Sabbat e12, Sony WF-XB700 y estos Sennheiser son los que mejor sonido tienen.El diseño es minimalista y son discretos, a pesar de su tamaño, que no son los más pequeños del mercado. El estuche de carga es de un tamaño muy cómodo para llevar en el bolsillo del pantalón.Los cuatro puntos que me encantan de estos Audífonos son:La comodidad, la duración de la batería, la conexión sólida con el smartphone, y por supuesto, el sonido.Son bastante cómodos, casi no pesan, y te aíslan pasivamente del ruido exterior a pesar de no tener cancelación de ruido activa.La batería le dura hasta 7 horas sin interrupción sin tener que recargarlos en el estuche de carga.La conexión con el smartphone es super sólida. No he tenido ninguna desconexión o dropout durante la reproducción, aún si te alejas a más de 10 metros.El sonido es muy claro, escuchas detalles de los instrumentos que no se escuchan en otros audífonos. La tridimensionalidad del sonido, es decir, el espacio y separación de los instrumentos es impresionante para unos audífonos de este tamaño. Es lo más parecido a unos audífonos de diadema. Se disfrutan mucho viendo películas. Las frecuencias agudas, medias, y graves están presentes cuando los sacas de la caja, solo tienes que descargar la aplicación para personalizar el ecualizador a tu gusto y el preset se guardara en los audífonos. Los agudos son brillantes, los medios muy notables y los graves, créeme, no te decepcionarán, son super claros y profundos.No te los recomiendo para hacer deporte porque no tienen certificación contra agua. Si los quieres para este tipo de actividad ve por los Sony WF-XB700 (Que son los que yo uso para esto) o por los Sennheiser Momentum del modelo mas reciente, claro que a un precio más elevado.Se pueden emparejar hasta a 8 dispositivos. Solo tienes que abrir la configuración del Bluetooth, seleccionarlos de la lista, y se desconectaran automáticamente del dispositivo anterior.En las llamadas, el micrófono no es notable, pero es lo suficientemente bueno para realizar llamadas con el teléfono y te escucharán claramente.La aplicación agrega algunos extras como la personalización del sonido, los controles táctiles y las actualizaciones de firmware de los audífonos, que por cierto, tarda un montón.En resumen, si buscas como yo unos audífonos para escuchar música o películas sin perder todos los detalles con una gran sonido 3D, estos audífonos son para ti.Tiene una excelente calidad de audio con las frecuencias muy balanceadas, no tiene bajos exagerados pero una claridad excelente en medios y agudos, de lo mejor para escuchar música comprimida, más no para escuchar música sin compresión FLAC y WAV, OJO no es compatible con Conexiones Bluetooth de códex APTX HD ni ELAC así que no escucharás HI RES AUDIO solo el estándar de cálida media como AAC de apple y APTX de android.Preface: I am a professional pianist.These sounded ok when I listened to vocal music and violin tracks (unaccompanied by piano). However, anything with piano or orchestra sounded muddy in the mid-bass. Ten minutes of listening gave me a headache.In terms of the sound signature, there is a marked dip at around 220kHz (A below middle C). Consequently, Kissin and Schiff sound like they can't voice properly. I cross-referenced the same tracks with my hifiman re-600s (very neutral sound signature) to confirm. Bass under this frequency (where there is muddiness) is actually slightly louder, so to me these earphones are slightly v-shaped, though the treble is clearly louder than the bass.Sound quality aside, the earphones were very comfortable. They felt light in my ears and I was able to get a good seal with the pre-attached eartips. In order to get an ideal seal, the tips needed to be pretty deep inside my ear canals (also, any less deep made it feel like they would fall out of my ears), which unfortunately made the sound even muddier. I did try switching the eartips to ones of smaller sizes. This reduced the muddiness, however, the earphones felt like they would fall out of my ears if I turned my head somewhat vigorously.I did not like how sensitive the earphones were to touch. It was difficult to adjust the fit of the earphones in my ears without triggering a touch command on my device.Bottom line: these are probably fine if you don't require precision from your headset. Really horrible for classical music though. This is not an audiophile earphone.Controls are too sensitive - hang a lot of calls by mistake - I disabled the control now I get peace of mind.... but still not using it for phone callsIt does not automatically connect to the app - I have to connect manuallyThe app needs more functionality to choose which controls to enable or disable not a global disable or enableThe ear tips pull out when I remove the buds from the ear - they are too soft or maybe just badly designedA carrying case will add value to the buds this is for CX convenienceNice to have - and optional something to attach the buds to each other because it’s each to loose one of them - a piece of innovative string to make sure the buds can be secured on each ither while wearing them or it one drops it can easily be found or retrieved -