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Sennheiser HD660S Review

An established company with a stellar reputation for over 70 years, Sennheiser is one of the leading innovators in the design and manufacture of professional solutions for the audio engineering industry. With such an extensive history of excellence, you can rest assured Sennheiser is a brand that delivers.

So, let’s take an in-depth look at one of their most popular headphones in our Sennheiser HD660S review…

Sennheiser HD660S
Our rating:4.7 out of 5 stars (4.7 / 5)


The Sennheiser HD660S are some of the best open back headphones in the high-end range. Being open-back makes them more suitable for home use, in part due to sound leakage.

The HD660S is the successor to the excellent HD650 headphones. The HD650 headphones were extremely popular, and the new updates to the design are more about refining something great to start with.

Market advances…

The market for portable devices is as large as ever, and Sennheiser definitely had that in mind when updating the excellent HD650 headphones. Unlike the HD650, which needed quality amplification to get the most from them, the HD660S will shine and deliver with just about anything.

So, are these the best headphones on the market? Let’s see for ourselves in our review of the Sennheiser HD660S…


Having owned a pair of the HD650, the first thing that strikes us is the color change to a matte black finish, which we really like. The HD660S and the HD650 do look quite similar. They also have a very solid build, with the drivers being visible through a sturdy black metal Grill.

As with almost everything else Sennheiser makes, these are some of the most durable headphones you can find. We would expect nothing less from Sennheiser.


A new transducer was built for the HD660S, which Sennheiser suggests lowers harmonic distortion. This leads to a more natural sound. The driver features a 38mm dynamic neodymium magnet driver.

The lowering of the impedance to just 150 ohms means portable devices now have a better chance of powering the HD660S headphones. This wasn’t possible with the HD650.

The driver, transducer, and impedance work together to deliver a pair that is easily one of the best audiophile headphones on the market.


The HD660S headphones seem to clamp quite tightly on the head and may feel a little uncomfortable if listening for extended periods. The well-covered ear cups and headband are exceptionally comfortable and do help ease that tightness to some degree.

A little less clamp force would have been an agreeable solution. However, these still are some of the most comfortable headphones in this price range.

Open-back headphones do have considerable sound leakage at high volume levels. But this is fine as they are primarily for home use. That leakage does mean your ears get less fatigued if you are listening to excessive levels for long periods.

Enhanced airflow and built to last…

The idea behind the steel mesh over the drivers is for better ventilation of the drivers. This, according to Sennheiser, gives more control over air displacement. Therefore, the music can breathe and shine without overheating the drivers.

Both the padding on the earcups and the cables are removable and can be replaced if need be. This ensures these headphones can provide you with years of listening pleasure.

Steep price…

The price may be a little out of reach for the average music listener on a smartphone. However, it should still sit well with the audiophiles’ passion for sound quality.

The Sound

The frequency response is very similar to the HD650, but the HD660S does sound slightly more refined. The HD660S definitely sounds crisper when it comes to attack and delay, and relays a cleaner sound.

The bass is smooth and solid but not overpowering. It relies on the familiarity of its predecessor to re-establish some of its merits. As with open-back headphones, the bass is often not as pronounced as a closed pair. If you are looking for a tougher bass response, the HD660S might not be for you.


A superb job has been realized here, with a tremendous balance achieved. The mid-range has no sense of hardness about it. Vocals and instruments sound rich and really shine as they hit their mark. Some engineers have suggested that the open-back headphone is less controlled here, but we didn’t feel that.

In the high-frequency range, we find a highly detailed treble. It does not feel sibilant and delivers a smooth yet unexceptional quality that gives you just enough of the right energy without relaying any harshness. We do think Sennheiser has hit a home run here.


Like the wonderful HD800 to some degree, the HD660S excels in its excellent soundstage. The stereo and spatial imaging relayed by the higher-end models in the Sennheiser HD range is always exceptional, allowing you to delve deeper into musical arrangements.

Put on some of your favorite songs, and the soundstage on these headphones will have you grinning. You will find yourself picking out the positioning of instruments and richness in frequencies you may have missed before.

What’s in the box?

Along with the HD660S headphones, you receive two 3-meter interchangeable cables and an adapter. One cable has a large jack plug, and the other a 4.4mm pentagonal connector. The adaptor allows connection to mini-jack sockets. All the included connectors are gold-plated, which helps protect against long-term corrosion.

The headphones are delivered in a splendid black box, within the form-fitting foam, and the Sennheiser logo emblazoned on top.

Sennheiser HD660S – Specifications

  • 38 mm dynamic speaker drivers.
  • Frequency response: 10Hz to 41kHz.
  • Impedance: 150 ohms.
  • Sensitivity: 104dB/V.
  • Type: open-back, over-ear stereo headphones.
  • Weight: 260 grams.
  • THD+N: <0.04%.
  • 3-meter detachable cable with a 6.35-mm connector.
  • 3-meter detachable cable with a balanced Pentagonal connector.
  • Removable ear pads.

Sennheiser HD660S Review – Pros and Cons


  • Great soundstage.
  • Design.
  • Comfort.
  • Can be used with portable devices.
  • Price.
  • Presentation.


  • At this price, we don’t see any.

Looking for Something Else?

Personal audio equipment is a necessity in today’s world. So find what you’re looking for in our in-depth reviews of the Best Headphones Under $200, the Best Bluetooth Headphones Under $200, the Best Sony Headphones, the Best aptX Bluetooth Headphones, and the Best Headphones with Microphone you can buy in 2023.

You may also want to check out our comprehensive JBL LIVE 300 Review, our Samson SR850 Review, our Turtle Beach Elite Atlas Review, our Sennheiser HD-800 S Review, and our Sennheiser Pro Audio HD 25 Professional DJ Headphone Review for more items currently on the market.

Sennheiser HD660S Review – Final Thoughts

The Sennheiser HD660S are some of the best-sounding over-ear headphones we have looked at. They will elevate your listening experience to new levels of enjoyment, especially when listening at home. The soundstage has to be experienced to totally appreciate and comprehend the difference it makes to musical arrangements.


The change from 300 ohms to 150 in the HD660S does not seem to affect the experience, or at least it wasn’t something we noticed. The changes made from the HD650 to the HD660S are minimal, but you do get to use your portable devices to full effect.

Sennheiser HD660S

However, being open-back headphones, we don’t think you will be using them while using public transportation. With that said, these headphones are still eminently portable and compatible with a variety of devices.

Final words…

Although the Sennheiser HD range of headphones may be out of many people’s price range, they truly are exceptional. You are sure to get a high-quality immersive listening experience that is well in line with the steeper price tag.

Until next, happy listening.

5/5 - (17 votes)

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About Corey Hoffman

Corey is a multi-instrumentalist who has played in numerous bands over the years, some good, some not so good. He has also written countless songs and recorded five albums in professional studios across America. Today he is a hobby musician but still loves the guitar after over 15 years of playing.

He considers his writing as a way to share what he has learned over the decades with younger generations ad always can't wait to get his hands on the latest gear.

He lives just outside New York with his wife Barbara and their two German Shepherds, Ziggy and Iggy.

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