Review: Sennheiser HD599 open back headphones

I’ve had these for three months now and have been using them as my primary headphones for that time. I have them attached to my Sennheiser (now branded Epos) GSX-1000 external DAC/amplifier running under Windows 11.

First, some background on the appearance of the headphones themselves. The set I have are in the ivory and brown colorway where the velour ear cups are in brown, along with the headband, and the remaining plastic shell is ivory. The mesh covers for the sides are black with brushed aluminum accents featuring the Sennheiser logo. They’re also available in black with aluminum trim accents should the ivory and brown colors not be your preference. I find the look unique and somewhat nostalgic, reminding me of the era of beige electronics with chocolate wood veneer trim and of Noctua fans which sport a very similar set of colors.

For construction, they’re yet another example of Sennheiser’s quality. The mesh for the open ear cups is sturdy metal, the housing itself has decent flex and is largely free from creaks and has no rattle whatsoever. It came with two cables as the headphones have a recessed and locking terminal offering easy replacement. One is a 3 meter cable and the other is 1.2 meter, which offer 6.5mm and 3.5mm plugs respectively. Also included is a 6.5mm to 3.5mm jack adapter. The cables are coated in a smooth and soft black rubber coating and the adapters are all gold plated. The recessed port in the headphones features a small notch that lets you twist the cable to lock into position securely and snugly. There’s no play or rattle when locked into position.

The housing is free of defects and has no points which feel rough or unfinished. There are no exposed sharp edges, even when the headphone band is expanded for larger heads. All edges are rounded and smooth to the touch, and importantly for me and my long hair, are well designed to not snag hair which is an issued I have faced with other headphones from various manufacturers over the years. The padding is firm but offers enough give to conform to the curves of my head. Clamping pressure is strong enough for them to remain secure on my head whilst gaming, listening to music, or chatting online, yet offers fatigue-free wearing for me for hours at a time. Padding on the band is covered with dark brown synthetic leather that is soft and smooth with fine and even stitching. It covers a thin, but adequate, layer of soft foam that offers enough resistance to prevent the band from directly resting upon my head, allowing the weight to be spread across most of the band rather than resting at a single point on the crown of my head.

They’re one of the best headphones sets I’ve ever worn when it comes to their comfort. They don’t develop pressure spots and even when wearing glasses, as I do, they don’t clamp hard enough to cause the frames to dig into the sides of my head. As they are an open-back design they also don’t build up heat and I’ve not had any issues of getting too warm around my ears wearing them. The ear cups are deep enough that my ears do not touch the inside of the cups either which helps prevent fatigue and heat buildup. The sound is also not fatiguing from being overly analytical and sharp which makes them excellent for longer sessions. As they are rated at 50Ω rather than the 25-30Ω of my other headphones I maintain a higher volume setting to drive the same level of sound output. For most days I run them between 30-50% as I find that range ideal for comfortable listening, especially for longer term listening.

My previous experience with higher end audio has been with Audio Technica and their ATH-HD700 and ATH-700X headphones which are also open back, low impedance, fairly neutral headphones. Between the three sets, the HD599 have the strongest bass. Not to say they thump my head, not at all. As an open back design, they inherently let in, and out, a lot of sound. 

Open back, describes the ear cups and their housing. There are three types, you’ll typically see: closed back, semi-open, and open back. Closed back are fully sealed; sound is kept isolated from the environment and often sacrifices sound stage (how ‘big’ the sounds feel, like whether you perceive the sounds coming from very close to your head or further away). But that sacrifice comes with stronger bass and far less environmental sound leaking in. Open backed are, as the name implies, the opposite. They offer very little separation from the environment such as your keyboard or a television next to you but in turn offer a far larger sound stage as the sound is allowed to leak out and fill around you. This also comes at the cost of bass as without those lower frequency sounds being held within, they largely escape. I personally don’t get into the nitty gritty of argument for exactly how open or closed semi-open designs should be, but they are a hybrid approach and attempt to gain the strengths of both whilst reducing the weaknesses.

Having said that, different designs always have different sound signatures. In the case of the HD599, they offer a stronger feeling of bass compared to my ATH-AD700(X) sets. I find it strong enough that I’m able to enjoy all genres of music I’ve listened to with them which covers pretty much any overarching genre from classical, to metal, and to electronic music. Listening to Caramella Girls, for instance, I’m able to make out details across the spectrum. The singers’ voices are clear and defined, and easily understood. Simultaneously, the bass strikes are present and up front.

Switching genres to an orchestrated soundtrack, Ludwig Göransson’s Mandalorian score is beautiful to listen to on these headphones. Horns and strings don’t fight each other for attention, instead both are distinct and separate from one another, allowing me to hear the details and nuance of both. Continuing to Natalie Holt’s score for Loki and it’s much the same. I can hear and feel the drums when they come in then make way for the softer notes of the synthesizers, all while keeping track of the gentle constant tick of the metronome in the background, even during the drums. I’m able to make out her gentle usage of distortion in a way I was unable to find when watching the show on television, even with a full speaker setup.

Channel separation is wonderfully clear and flows between the right and left fluidly, such as in The Cars’ Moving in Stereo. Hearing the voices and instruments flow between the sides so smoothly is a fantastic listening experience and something that is often lost with poorer headphones that don’t maintain that level of audio separation. For songs like that, where right and left channels are distinct and separate, such as found in Pink Floyd’s The Dark Side of the Moon album, this makes the experience of the music so much more alive. Combined with the phenomenal frequency separation allowing the gentle tapping of the cymbals in time to be as clear as the enthusiastic saxophone while the electric guitar is strummed along allows me to just fall deeply into the music. It separates the ability to listen to music from the ability to experience music. Much like how food without seasoning becomes a completely different experience when the same ingredients are seasoned.

For music these are my favorite headphones that I own. As much as I love the striking detail of my ATH-AD700X their lack of punch is almost striking in comparison. For different genres of music, where low frequency bass isn’t as crucial, I still adore them. But, for an all-around listening experience? These HD599s are what I would choose every time. No matter what I throw at them they remain composed, clear, and offer enough of a thump to make the experience fun and exciting for me. Hearing Freddie Mercury’s vocals is an absolute treat. And hearing the synthesizer of Wendy Carlos is just as beautiful. When it comes to musical prowess the HD599 are a fantastic choice.

These strengths carry on to movies as well. Whether it’s quiet whispers, droning engines, or the flowing of water, they replicate those sounds with aplomb. The channel definition and separation also find strength here, allowing me to find directionality of sound as well. Dialog, what I find most important to shows and movies, is particularly clear and well produced. Much of what I watch involves heavy dialog such as with documentaries or dramas and I’ve never found them lacking in my ability to hear and understand them, even allowing me to hear background conversations.

Finally, onto the other main use I have for them: gaming. I find for gaming they continue their excellence. They offer a large sound stage, excellent separation, and great positionality. In Forza Horizon 5 the various car engines and upgrades are distinct and sound powerful. I enjoy being able to hear the waste gates twitter from the various turbos as well as the building whine and whistle of the superchargers. Hearing the gravel and dirt getting tossed by the tires, or the screeching of those tires trying to find traction on the tarmac, both are satisfying and add to the feel of the game.

Open world games feel alive and open. Games like Fallout 4, Skyrim, and Grand Theft Auto V all sound open and large. Sounds in the distance sound far away, and close sounds feel close. I do have to say though, they aren’t quite as distinct as the ATH-AD700X when it comes to positionality. Pinpointing sounds comes more easily with those, they feel even more open. But explosions and other deep and rumbling sounds lack punch. The HD599 are a good compromise for that, offering more power to those sounds. It comes down to genre as to which headphones I prefer over which. For open world games, for games in large locales I feel I would give the nod to the Audio Technica headphones. They make their way further out in such a way that they are the most open sounding. But, for smaller areas, for corridors inside buildings or for games where I don’t need to pinpoint a sound to such a degree, such as in Half-Life or Civilization V, I find it a wash between those and the HD599. Both are absolutely excellent, and I’d take both over any of my closed back headphones, even over my Sennheiser/Epos GSP 300 headset, at least so long as the environment is quiet enough to not offer distractions away from the sounds.

In that regard, if I am in a louder environment, I do like going back to my GSP 300. They separate me from the environment so much more as they are closed. And that is largely the consideration for your usage scenario. If you have a noisy environment, whether roommates, pets, family, or what have you, an open back design may simply not offer what you’re looking for in headphones. If your goal is to separate you completely from your environment you will want closed back, no question. If, however, you want to have a more expanded sound stage and listen in a quieter environment you might just find yourself in awe of just how much more there is to hear in your favorite songs, movies, and games. Sounds you didn’t even know were there might just pop in to say hello for the first time for you, and that’s an amazing experience. And, when it comes down to it, if that is what you’re looking for the Sennheiser HD599 are an excellent choice. 

Finally, to price. The MSRP for the HD599 is $249.95. The aforementioned ATH-AD700X MSRP is $199.95. These aren’t cheap headphones, nor are they anywhere near the upper echelons of audio equipment. I consider them as more entry-level audiophile or enthusiast models. The good news is that both are typically available for far under MSRP. I purchased my HD599 for instance for $149.50. I see they are currently $149.95 on Amazon and the ATH-AD700X are $118.72. I think both are well worth those prices, and even at full retail price given the quality of them. I think both are excellent and neither would be a bad purchase. I’ll review those Audio-Technica headphones later as well but for now I do suggest the Sennheiser HD599 as an excellent option for you if you’re looking for a high quality pair of open backed headphones.