HD 660S2 - Audiophile Open-Back Over Ear Headphones with Deep Bass Extension and Refined Acoustic Performance, Over-Ear Headphones for PC, Music, Gaming, Podcasts, Premium Black

Update on August 9, 2024: The iFi DAC combined with the iFi Zen Can produced clear sound and proper dynamics, but human voice sounded feeble and harmonics were missing (that is, a concert piano sounded like an electronic one). I figured it was the amplifier, not the headphones, so I gave a try to an XDUOO TA-10R, which is a hybrid headphone amp, using a balanced tube and Class A amplification (USB, optical, RCA, and coax inputs, a pseudo-balanced output that still sounds better than the 6.3mm unbalanced one). Once I swapped out the factory tube for a Gold Lion, the sound stage opened up, human voice became full, and the harshness around the high C vanished. Even poor recordings (uncompressed) sound good, providing a lot more presence than I experienced from the iFi combo. The fullest sound that goes deepest uses a Tungsram tube. I must admit that a $40 Koss would probably meet most people's need. Also, as my old friend said about 50 years ago, no headphone can compete with a good room setup (which can be hilariously expensive, but not necessarily. Compiling it from used items, you can get one for around $10k, which is still a lot less than the top-of-the-line headphones that still can't compete with it. Original review from May 24, 2024: Every time I put them on, I feel mesmerized. Have never had this experience with any other headphones; it's like the music comes to life around my head, as if I was present at the performance. Granted, that applies mostly to classical music, and the sound can easily bring tears into my eyes. Still, these babies produce excellent sound for everything I've put on them. I'm not a gamer, so I can't comment on the gaming performance, but there is at least one 5-star review on that subject. Anyway, beyond the subjective, sources and recordings are also essential to consider as well as the connections, so let me submerge into those details. Good headphones are no good for compressed sound, but plenty of headphones are made for such a clientele. The s2 with its refined sound is targeting an audience that cares for the original sound. Please, notice that when people "burn in" new equipment, during much of that (except for diaphragms in speakers), what happens is that the components adjust to each other, especially on the analogue side. The outcome ultimately determines if their combination is feasible or not. My current setup has been serving me well in the last five years or so, so I haven't made any changes. I used an iFi Zen DAC v1 (from the USB port on computer) and an iFi Zen Can v1 (on the RCA input from a relatively high-end LG Blu Ray player from the optical port through a digital-to-analogue converter). Connected the DAC with the amp through their balanced ports with a short decent balanced cable. Both amps were hooked up to the sources with SVS interconnect cables. Didn't use the "Trubass" feature on either one, because for my taste, it upsets the sound balance (the DAC also amps the bass at a higher frequency than the amp). My sources were the usual high-resolution recordings (both pop and classical) and Blu Ray movies I use for testing new components. The most prominent strengths of the s2 is extended bass and an adherence to the original sound signature. While the OEM cables are fine, out of the two supplied, I favor balanced one. I have found a purchase for a previous Sennheiser that didn't work out at the time giving me better resolution. Amazon is still selling it: KK Cable II-SO. (Added on 6/28/24: for movies, the original balanced cable works better; the KK produces less bass in return for better instrument positioning, and dialogues suffer from human voice being elevated around 500Hz, which makes conversations harsh and unpleasant to listen to. The original cable goes deeper, although perhaps a bit muddied in the lowest end, but conversations are clear). The only problem with the extended bass is that the housing loses a little control over it beyond a certain (obviously VERY high) volume, so I can sort of feel the ear cups moving, which breaks the illusion of being present. This is probably the main reason why the pressure around the ears is relatively high (and loosening it might not be the best idea). The s2 might not be the best for someone with a large head (it might feel uncomfortably tight) or unusually large ears that the ear cups cannot cover, and it took me a few days to get used to it, because I am on the high end of average head and ear sizes. The included bag is a plastic dust collector; I am using an anti-static bag instead. Hard cases are available for transportation, but the original box works for that, if only on occasion. As opposed to the planars I've heard (Moondrop Para and Hifiman HE400se, but others report the same problems with lot costlier planars), the s2 retains the familiar sound on the recordings I usually use for testing new equipment, and it extends the listening experience in gentle, but important ways. The bass reverberates in the concert hall, and is not victim to extensive channel separation. Even harmonics play the same or better than on anything else I've heard in this price range or below, although this is a feature that can warrant higher investments. No problem with high-pitched human voice being harsh and sibilants don't suppress other frequencies; the performance is actually toned down a bit in order to retain the sound that recordings must have been meant to sound like. In my understanding "warm sound" is often used for describing the feature, perhaps because no highs and mids dominate at the expense of the bass or each other. Despite the somewhat reserved (but not veiled) presentation, the dynamics don't suffer. I believe, the secret is ingenious engineering that uses physics: the proper driver and built-in sound paths in the earphones. Many other headphones have built-in electronics in the sound path, allegedly, to protect the user's hearing, but to me, it seems more like protecting the drivers from overload. Consequently, the s2 doesn't clip at low bass (emit a clicking sound, while cutting out the sound), while most the sound is there in that region, too. The headroom is like sitting in the concert hall, albeit a bit further in the back that the eight row, but the sound image remains steady at various volume levels. To me, the harmony and the unity of the sound, along with the original sound signature, is worth the price. Added on 04/03/25: The best cable I've found for these is https://www.amazon.com/gp/product/B0BZMS68RV, although it lasted only for six months. The best amplifier in this price range is a hybrid tube (the tube is only for buffering a Class A headphone amp) is the XDUOO TA-10R. Added on 12/22/25 The best affordable tube headphone amp for these turned out to be a Fosi GR70, available on Amazon, where I also bought it for under $180.

Sennheiser HD 660S2 - Audiophile Open-Back Over Ear Headphones with Deep Bass Extension and Refined Acoustic Performance, Over-Ear Headphones for PC, Music, Gaming, Podcasts, Premium Black I’ve actually bought these headphones three separate times now. There seems to be an ongoing price war between Amazon and Best Buy to see who can drop the price the lowest, and I kept chasing the deal. If you can snag these for under $420, they are absolutely worth it. If the price jumps back up toward $600, keep an eye out for the refurbished models that pop up around $350—they are what the product should be priced at. I’m currently running these through a Fosi Audio DS2 (the 2024 version) for both my PC and my portable gear. I use the 4.4mm balanced connection, which provides plenty of power to really let these breathe. If you’re using a standard headphone jack, your results might be a little different, but with a decent little DAC like the Fosi, they shine. The standout feature for me is how intimate and lifelike the vocals sound. Because the DS2 has a very neutral, "clean" profile, it balances out the natural warmth of the 660S2 perfectly. It creates a really relaxing, rich listening experience that doesn’t get tiring after a few hours. I bought these specifically for critical music listening, and they nailed exactly what I was looking for. In terms of the actual sound, the "stage" feels a bit narrow and close to your ears—it’s not a wide, airy stadium sound—but the bass is warm and has a nice punch to it. It feels impactful without being overwhelming. I also own the HD 490 Pro and the Fiio FT1, and they all serve different moods. While the 490 Pro is wider and better for picking out every tiny detail in a mix plus I also use them for gaming using custom audio cables from Hart Audio, and the FT1 is a "disruptor" with deeper bass because it’s a closed-back design and under $170, the 660S2 is the one I reach for when I just want to get lost in the music. It’s a premium piece of gear that feels like a long-term investment for anyone who loves high-quality audio.

Son exceptionnel

Well…a few hours in and let’s say I am not overwhelmed. Very little difference between these and XM5s and maybe not so good. Returning.

Typisch Sennheiser sehr gute Qualität

Ok.The Skinny of it... A little rough in the edges but..still acceptable by listening standard. Compared to AT WP 900 this model is on the softer side and rougher on the highs. Compared to Grado SR60 the sound is compressed with this headphone. Compared to Sony MZR 2 the 1k version that is opened and not compress but you feel you want to play it louder. But no complains if you want to pamper yourself. Finally compared to the top of the line Focal 6k model. This one is bar none. Dynamics highs mid and tonal separation this is serious stuff. But Seriously all running on the same LG V60 as source with Tidal and with USB audio pro meaning it is forced to output 16bit. Not 48.... Final word for the price...we have to be fair for the quality of sound on the price. If you were to compare it with the AT WP900 same price but now with the promo the Senheiser is reasonable value for money. Atleast if you are thinking about giving this to your teenage kids.Fine with it. No complaints. Cause if you look at it in this way every 6months they will end up buying new cans. Cause the wires just snap but with the Senheiser you can easily replace them. All the parts sponge head sponge and the cables you can swap them when wear and tear approaches.Besides you only have 1pair of ears so either you take good care of them for the better part of your life or you end up loosing to be deaf as time and age passes by. Your choice. For me I will this model. It is fine for daily use.Reasonable.

Comprei o Sennheiser HD 660S2 buscando um salto real em qualidade sonora — e ele entrega exatamente isso. É um fone que muda a forma como você escuta música: você não apenas ouve, você começa a perceber camadas, texturas e detalhes que passam despercebidos em fones comuns. A assinatura sonora é natural, quente na medida certa e extremamente detalhada. Graves são presentes e bem controlados (inclusive subgrave, algo raro em fones abertos), médios são muito bons para vozes e instrumentos, e os agudos são suaves, sem fadiga. É o tipo de fone que te faz ouvir um álbum inteiro com atenção — Daft Punk, trilhas do Hans Zimmer e música acústica ficam simplesmente incríveis. O palco sonoro é amplo e bem definido, criando uma sensação quase “tridimensional”, mesmo sendo estéreo. Para quem gosta de ouvir música com calma, atenção e qualidade, é um fone excepcional. Pontos negativos (ou melhor, pontos de atenção): O acabamento é majoritariamente em plástico. Ele é bem construído, sólido e claramente premium, mas considerando o nível e o preço do produto, poderia usar materiais mais nobres como metal e/ou madeira em algumas partes. No início, achei o fone um pouco pesado, principalmente em sessões longas. Felizmente, isso melhora com o uso — o conforto acaba se tornando muito bom depois que você se acostuma. Considerações finais: Não é um fone “plug and play” para qualquer situação: ele se beneficia bastante de uma boa fonte (DAC/amp), e não é feito para uso portátil. Mas no ambiente certo, ele entrega uma experiência sonora de alto nível, que justifica plenamente o investimento. Logicamente o ideal é você ouvir músicas com mais qualidade (nada de radio online ou streaming que te entrega um audio mais compactado). Ele vai tocar bem, mas com a qualidade certa, a experiência sonora é superior! Se você gosta de música de verdade e quer subir de patamar na forma de ouvir, o HD 660S2 é uma escolha excelente.