A Little Historical Background:
I've owned Sennheiser headphones since the 1990s, starting with the open HD 320 in their Expression series.
Sennheiser announced their new HD 500-series headphones in Fall 2016. The HD 500 series is a premium headphone product designed for home listening. There are open and closed designs in the 500 series. The HD 599 is an open design headphone.
I picked up this pair (HD 599 SE) in 2019. The colorways, cream/brown in the regular model and black/silver in the SE, perform identically. The HD 599 succeeded the previous model, the HD 598 (launched in Fall 2010). The HD 599 comes from a long lineage of successful and popular headphones, particularly as lightweight open design cans.
* It's important to note that while the HD 599 are still widely available, they have been succeeded by a newer model, the well-regarded Sennheiser HD 560S, available since Fall 2020. I think the HD 599 SE is better-looking than its successor, which looks a bit plain in all-black, but I haven't listened to the 560S yet.
The Sennheiser Flagship Family
It also lives in a lineup where there are more expensive headphones like the HD 660 S2 and HD 800 S, with the $50,000 electrostatic HE 1 headphone and amplifier combination at the very top.
With discounting, you might sometimes compare the HD 599 at regular price against older models of the 600 series like the Drop HD 600 and HD 650. However, there isn't a direct comparison when you look more closely. First, the HD 599 and 599 SE are often discounted, so expect to pay much less than the list price if you can wait.
The HD 600 and HD 800 series have a nominal impedance of 300 ohms, so they are much harder to drive with mobile audio players and standard laptop jacks. You may need a dedicated headphone amplifier to drive the HD 600 and HD 800-series properly. Also, the HD 600 series has a higher clamping pressure, so you may find the HD 599 more comfortable for long sessions of casual listening and gaming use, etc.
The HD 800 series lives at a much higher price point, so they are not directly comparable to the HD 500 series products. The ring radiator drivers are a different design compared to the HD 599's more conventional dynamic driver and their sound signature has been considered somewhat divisive.
How Do They Work?
I'll re-emphasize that these are open design headphones intended for home listening. I have seen people wear them on the street, but their size, light clamping pressure, and balance make that a tricky proposition, combined with their complete lack of noise isolation.
The HD 599 comes with two cables, each terminated with a proprietary locking plug to prevent accidental disconnection. The 1/4" plug has the longer cable at slightly less than 10 ft (3m) and the 1/8" plug has a short cable at 4 ft (1.2m). Sennheiser also includes a 1/8"-to-1/4" (6.3mm to 3.5mm) adapter.
Each of the earcups has an adjustment to accommodate larger and smaller heads, and you can twist them slightly on the z-axis as well, so there is a wide fitment range for different head shapes and sizes. The velour earpads are replaceable, and I haven't noticed any wear in my long-term ownership.
With a nominal impedance of 50 ohms, the HD 599 is easy to drive with most mobile players and laptop jacks. You may notice some creaking from the plastic joints if you move your head, but I haven't found it to be overly distracting.
How Do They Sound?
Amazing. For the price, and on an absolute level, the HD 599 are a pleasure to listen to. For many people, the HD 599 will be the best headphone they ever buy, and that is a wonderful thing, particularly at its most discounted price.
The 599 never had any burn-in effect that I could notice. They sound the same fresh out of the box as they do years later. I like to put a lot of music through my headphones before I make any judgments about them.
They do have a slight elevation in the treble and bass areas of the frequency range, but the overall tonality is warm and forgiving of poorer recordings, unlike many premium headphones. There is no Sennheiser Veil - music is neither recessed nor overly forward in its signature.
Sennheiser uses "Ergonomic acoustic refinement” (E.A.R.), which may be a fancy way of saying angled drivers. Soundstage is good and imaging in well-recorded music gives you accurate spatial cues and air.
In general, the 599's sins are of omission - yes, there is a slight coloration, but a pleasing one. You won't hear anyone describing the 599 as thin, sterile, clinical, or glaring. Its treble emphasis is subtle, the bass not overwhelming except in some extreme recordings, and the mids are clear and enchanting. It isn't hyper-detailed, but tuned for the enjoyment of music.
I listen at modest volumes and I have detected no distortion or noise. The HD 599 is versatile, excelling at electronic, pop, rock, jazz, classical, etc.
Today's test albums:
Chromeo - Un Joli Mix Pour Toi
Chromeo - Ce Soir On Danse!
Chromeo - DJ Kicks
Annie - Neon Nights
Daft Punk - Random Access Memories
Igor Stravinsky - The Firebird - cond. Antal Dorati, London Symphony Orchestra
Hilary Gardner - The Great City
Music with heavy or exaggerated bass may bring out its worst tendencies - if you have equalization, you may wish to decrease bass response in some genres. Turn off bass boost if your device has it.
Wired headphones like the HD 599 are considered old-fashioned by the contemporary electronics market. They don't have features like Bluetooth, microphones, active noise cancellation, or 3D spatial sound. However, music lovers don't need these features and adding them introduces compromises beyond the price tag - power limits and reduced audio quality from digital compression, batteries, and additional electronics in the signal chain.
Upgrading?
Because of the HD 599's design, some owners may be tempted to tinker, starting with aftermarket cables and earpads and possibly progressing to driver modifications. My 599 is stock, so I can't comment on the efficacy of various mods, but I feel the stock 599 is best for most people. I do recommend getting a spare set of earpads from Sennheiser if you plan to keep them for a long time.
I think the HD 599 benefits marginally from headphone amplifiers - give it a good source and it will perform well. It does not demand high power, but it is capable of scaling with better equipment at a modest level.
Conclusion
The HD 599 is a great headphone. It may not impress the wealthiest audiophiles, but they are good enough for most listeners in all genres of music and even for other uses, like gaming. That may sound like I'm damning them with faint praise, but it's the opposite - you are getting a huge upgrade in sound quality at a reasonable price.
If you check other reviews, people often compare them to much more expensive headphones. The HD 599 is a great starter headphone and possibly an even better endgame headphone for music lovers. It illustrates the law of diminishing returns very clearly - there are better headphones, but you'll have to pay much more for incremental gains in audio quality.
