IntroductionI recently purchased the Hifiman HE-R9 over-ear headphones and ultimately didn’t get on with it and exchanged them for the Deva Pro’s - and boy am I glad I did. I won’t go into details on the build-quality and technicalities of the R2R Bluetooth module - needless to say there doesn’t appear to be any issues with my units - even the battery life on the Bluemini appears to be acceptable to me. What’s more important for me however is the sound quality.Sound QualityAll I can say is WOW!!!! I have been an enthusiastic headphone user for many years now and have gone through many different headphone types - Balanced Armature IEM’s, On-Ear, Over Ear, TWS - I’ve even tried the Jecklin Floats (many years ago) - nothing I’ve tried in the past sounds as good as the Deva Pro’s. Whilst the soundstage may not be the widest out there, the imaging is first-class. They kinda remind me of the Etymotic ER4P when it comes to imaging - instruments and performers remain where they are in the soundstage - not wondering around. It's remarkably easy to choose and follow a specific instrument or performer in the mix and focus on them effortlessly. There's not many headphones in my collection which offer this degree of ‘fidelity’.Whilst it’s fair to say that these are not bass monster headphones, they still offer a wonderful degree of detail in the lower registers - albeit with a slightly softer presentation. A professional bass player would definitely be able to accurately identify the individual notes on most recordings without difficulty. Other headphones where I have experienced this degree of resolution in the bass are the Etymotic ER4P in ear monitors. Again, these couldn't be described as bass monsters by any means, they still have the ability to accurately convey bass notes in a detailed and coherent way.Mids also show this level of detail without ever feeling oppressive or overwhelming. There are some headphones and IEM's out there that are famed for their midrange detail and some of them can come across as quite hard and relentless in the presentation of the mids - sure the details are there but they can sometimes be a little too much ‘in your face’ for my liking. Vocals on the Hifiman Deva Pro's are wonderfully natural sounding. I listened to some early Queen - I know they're not the best recordings in the world but my God Freddie's voice really had detail that I honestly had never heard before. Interestingly I recently purchased the infamous KZ Pr2 HBB Planar Magnetic IEM’s - fairly intense sound out of the box but when sufficiently broken in, re-tipped with my favourite triple flange tips and fitted with a new balanced cable, do sound remarkably similar to the Deva Pro’s - they definitely both share the ‘Planar Sound’.When it comes to treble, again, the Deva Pro's really shine. Treble in one area where I sometimes feel I'm too sensitive - one aspect of the HE-R9's was the smooth treble response - never harsh or fatiguing but also, on those headphones at least, far too laid back for my tastes. The Deva Pro's strike the perfect balance in my opinion. Whilst there's details galore in the treble region, I've yet to find them even remotely fatiguing.The overall sound character of the Hifiman Deva Pro is similar to my Sennheiser HD598sr in a way. Whilst initially the bass appears to be somewhat lightweight when compared to the other frequencies, you realise that the bass is there and presented very cleanly - no bloat - just the natural bass sound. They also go deep when required. I feel that there’s a slight dip in overall dynamics when compared to conventional headphones - it feels that there’s a slight ‘levelling’ to the sound - which does actually make it a little easier to find your ideal volume and not have to continually make micro adjustments when there’s a more intense part of your music playing. I personally like this but do understand why some people feel that there’s still a way to go when it comes to Planar Magnetic headphones. To each their own I guess.One point worth mentioning is that these headphones leak like nothing else out there. Everyone will be able to hear your music - my wife has commented several times that I’m listening to music too loudly and I’m going to damage my hearing. All I usually say to that is “You What???” and carry on listening. My point being that these are definitely designed to be used in a quiet environment - not whilst out and about - I’ve got the Sony’s (and several others I’m embarrassed to say) for outdoor duty - no worries there.ComfortYup. They're comfortable. Fairly lightweight and with a reasonable clamping force, there's really not much more to say about these - I've worn them for several hours at a time without any significant discomfort and, like my Sennheiser HD 598 SR, they completely encapsulate my ears and the cups are deep enough for my ears to not touch the material covering the drivers. The fit also increases the width of the soundstage somewhat and while this doesn't offer the intimate sound character you would get with IEM's, it still resolves the sound nicely. I would say that the Sennheiser HD598SR is slightly more comfortable but not by that much. For me, the headband doesn’t really cause many problems but I can imagine some people may not get on so well with it. There are retro-fit kits available which offer an alternative ‘sling-like’ headband but I’m more than happy with mine.BluetoothThe R2R Himalayan external Bluetooth dongle attaches to the left earcup - offers only basic controls (on/off and Play/Pause) but does sound incredible. Most of the time I feed the Deva Pro's wired via the excellent Fiio BTR7 Bluetooth DAC/AMP and to be honest, the only significant difference between the Fiio BTR7 and their Bluemini adaptor is number of volume steps offered by the Fiio - it's far easier to find the ‘sweet spot’ volume wise with the Fiio set-up. The Bluemini's volume steps are far too coarse and I have resorted to installing an additional application to help get back a little control over the volume. From a pure sound quality perspective there's no appreciable difference between the two sources. Bluetooth range is definitely better with the BTR7 though. Battery life is a little disappointing - although you're pretty much sure to get through a single listening session on a full-charge, the fact that you're only good for around 5-6 hours when using LDAC at higher volumes, means that you're going to have to charge the unit more often - resulting in excessive battery wear due to constant recharging. With this in mind, I tend to use the headphones in wired mode most of the time. Still, it's nice to have the option and it's nice to not have to compromise on sound quality when you do use it.There’s no significant noise floor with the Bluemini. The Bluemini can drive the headphones to very high levels - far higher than you would ever be comfortable with in my opinion. However once you go above a certain volume level the sound can become quite hard and fatiguing - however it has to be said that this is only when you’re driving the headphones really REALLY hard.ConclusionIn case you haven't figured it out yet - I really like these headphones. They're definitely at a higher tier than my Sennheiser HD598 SR's and are suitable for a wider range of musical genres in my opinion. They do require decent amplification in order to get the most out of them. I suspect they would benefit from a balanced cable - something I may well purchase in the future. The Bluemini R2R bluetooth module actually does produce a ‘balanced output’ and offers truly excellent sound quality - at a cost of pretty poor battery life. In all fairness they last long enough for a prolonged listening session. The primary problem is that because you’re going to be charging it up more often which results in a battery with a limited lifespan. The other problem with the Bluemini is the coarse volume steps - something that can be slightly alleviated with a software fix. In all fairness though, if you want a bluetooth headphone with all the bells and whistles, get a Sony. If you want a wireless headphone where the only significant aim of the designers is sound quality - get the Hifiman Deva Pro.Are there better headphones out there? I honestly can’t comment on this because these are the best full-sized headphones I have tried so far. I think for their current price buying them is a bit of a non-brainer. They’re cheaper than Sony’s over-ear bluetooth headphones and, whilst the Sony’s have a lot more features and excellent active noise cancelling, they don’t come close to the Deva Pro’s when it comes to sound quality (although I have to admit I still like the Sony’s a lot). I’m very pleased with my purchase and I would highly recommend them to anyone looking for a really good pair of full size headphones at around this price point.