Drop HD6XX vs Sennheiser HD660s (Headphones Compared)

Sennheiser HD6XX vs HD660S

The Drop x Sennheiser HD6XX is one of the most significant headphones to have come out in the last couple of years. It has successfully repackaged the Sennheiser HD650 at a more budget-friendly price point. 

However, the Sennheiser HD650 is not a new headphone. It has been around since 2003. And while it is still a great sounding headphone today, there are now lots of newer options that can potentially offer a better experience. 

One of these newer headphones is Sennheiser’s very own sequel to the HD650, the new Sennheiser HD660S. It boasts various improvements to the HD650’s sound quality and successfully manages to lower the power requirements, theoretically making the HD660S a technically superior headphone. 

But, of course, these improvements don’t automatically mean that it is better than the HD6XX. The HD600 still remains significant today despite the various revisions that it had.

In this article, we will be helping you decide whether the HD660S is worthy of its significantly higher asking price. We will be going through the various differences between the two headphones. We will also help you decide which headphone is better for your use case. Keep on scrolling to find out more. 


Sennheiser HD660s vs Drop HD6XX

Sennheiser HD660S

Sennheiser HD660S (Image: Stephen Menor)

Read our Full Sennheiser HD660S Review

The Sennheiser HD660S is the latest revision to Sennheiser’s legendary HD600 Series. It is the direct follow to the HD650 and improves most of the shortcomings of its predecessor, making it a more modern and competitive headphone. Also, aside from improving the HD650’s sound, the HD660S also incorporates the neutral and analytical approach of the HD600. 

Sennheiser x Drop HD6XX

Check on Drop

The Sennheiser HD6XX was one of Drop’s first headphone collaborations. It is based on the legendary Sennheiser HD650 and pretty much changed the game since it made the HD650’s more affordable. And it was able to do this without sacrificing any of the key features of the HD650. 

Build Quality 

Sennheiser Open back headphone

The Sennheiser HD6XX and HD660S are very similar in terms of their design and build quality. Both headphones are mostly made with high-quality plastic. This gives the headphones their lightweight nature, which makes them comfortable for long listening sessions.

Despite being made of plastic, the HD600 Series headphones are known to be very durable. And if any part breaks, official replacement parts from Sennheiser are available. Anything from the headband to the drivers can be replaced. 

Both headphones are also utilizing the proprietary Sennheiser 2-Pin cable, which is pretty reliable. The proprietary connector shouldn’t scare you since replacement and aftermarket cables are pretty easy to find.

It should be noted that the cable that comes in the HD6XX and HD660S have different terminations. The HD6XX comes with one cable that terminates in a 3.5mm SE jack. The HD660S, on the other hand, comes with two cables. It comes with an unbalanced cable that terminates in a 6.35mm jack (with a 3.5mm adapter) as well as a balanced cable that terminates in a 4.4mm Pentaconn cable. 

Sennheiser HD6XX earpads (Image: Drop)

There are some slight differences in the aesthetics of the two models. The Sennheiser HD660S has a sleeker all-black color scheme, with the Sennheiser logo being found on the left side of the headband. The HD6XX has a dark blue finish (officially called midnight blue) and has the HD6XX branding on the sides. 

Additionally, the HD660S’ grills and drivers look different from the HD6XX. We’ll talk more about this new driver in the sound quality section. Overall despite the massive price difference, the build quality of these two headphones isn’t very different. This is a testament to the HD6XX’s unbeatable value for its price point. 

Power Requirements 

ifi nano bl with hd660s

One of the major differences between the two models is the power requirements. The Sennheiser HD6XX has an impedance of 300 ohms, while the HD 660S has a reduced impedance of 150 ohms. If you are not familiar with the term headphone impedance, you can check out our dedicated article

But to make things short, headphone impedance is one of the factors that determine whether or not a headphone will require a headphone amplifier. Since the HD6XX has a high headphone impedance, you will need a headphone amplifier to get the best results. 

The HD6XX isn’t very hard to drive compared to other high-impedance dynamic driver headphones. Entry-level headphone amplifiers such as the Schiit Magni 3, Liquid Spark, or Zen DAC/Zen CAN should be able to drive it fairly well. It will still work with smartphone dongles or onboard sound cards, but the sound will be more congested and will be less detailed. 

The Sennheiser HD660S, on the other hand, is much easier to drive thanks to its lower impedance. It can be directly connected to your PC’s onboard soundcard, smartphone, audio interface, digital mixer, or gaming console. 

This isn’t a bad thing, nor is it the first time that we have seen a successor with a lower impedance. The latest version of Beyerdynamic’s flagship headphone, the Beyerdynamic T1 3rd Generation, has also lowered its impedance from 600-ohms to 30-ohms. 

The lower impedance can be very important for individuals such as musicians who want to directly hook the HD660S into their audio interface or digital mixer without needing any additional headphone amplifier. This is also important for gaming consoles, such as the Nintendo Switch, that cannot connect to most external DAC/Amps. 

But with that said, we still advise purchasing a DAC/Amp or headphone amplifier for the HD660S. The HD660S scales well when fed with more power. Its sound opens up, and the detail retrieval across the board is significantly increased. 

If you are upgrading from the HD6XX and have already purchased a headphone amp or DAC/Amp, then those will work just as well with the HD660S. 

Sound Quality 

Drop HD6XX Build
Drop x Sennheiser HD6XX (Image: Drop)


Winner: Sennheiser HD660S

One of the main criticisms of the HD600 series is their bass response. Compared to planar magnetic headphones and other dynamic driver headphones, the bass is relatively thinner and less extended. They are still present, but they won’t have the same satisfying punch and impact as other options such as the HiFiman Sundara

This doesn’t mean that the bass response is bad. The HD6XX, in particular, is able to give a realistic and well-defined low end. It may not have the bass quantity to compete with other headphones, but it more than makes up for it with quality. Also, having less bass leaves plenty of room for the mids to shine. 

But with that said, the HD660S is able to bring significant changes and improvements to the bass response. The bass on the HD660S is more prominent, is clearer, and more coherent compared to the HD6XX. It still doesn’t do bass with authority as the other options mentioned, but it is a lot better compared to both the HD6XX and the older HD600


Winner: Sennheiser HD660S

The main highlight of the Sennheiser HD600 Series is the mids. Both models feature forward-sounding mids that perfectly highlight the vocals. But out of the two models, the HD660S has the better technical performance. 

The HD6XX has a smooth and warm-sounding midrange that effortlessly reproduces instruments and vocals. The HD660S, on the other hand, takes the HD6XX’s satisfying mids to the next level. 

The approach of the HD660S is similar. However, it manages to add more clarity and more detail retrieval while still maintaining the HD6XX’s smooth nature. You are getting a more analytical and detailed sound without sacrificing the graceful approach of the HD6XX. 


Winner: Sennheiser HD660S

There aren’t any major issues when it comes to the highs of the HD6XX. However, compared to other options in the market, the highs are a bit toned down. This allows the HD6XX to avoid sibilance and maintain a smooth overall sound. 

The HD660S once again manages to improve the highs without sacrificing the smoothness that the HD6XX had. There are more clarity and more definition in the upper frequencies. Instruments and various elements are now a lot easier to hear in the HD660S. 

This may make the HD660S a bit more shouty for some people coming from the HD6XX. But overall, sibilance and harshness are always kept in check with the HD660S. 

Imaging and Soundstage

Winner: Sennheiser HD660S 

Both headphones have an intimate soundstage and fairly accurate imaging. However, the HD660S is noticeably better in both the imaging and the soundstage. 

The HD660S’ soundstage is a touch wider than the HD6XX. It is still not on the same level as the HD800S, but it is now more open sounding than its predecessor. 

The imaging is also more accurate than the HD6XX, presumably because of its better technicalities and more accurate upper midrange and high-frequency response. Gaming and listening to more complex music is more satisfying with the HD660S. 

Which Headphone is For You?

Better Value: Sennheiser x Drop HD6XX 

Drop HD6XX Side Grills (Image: Drop)

The better value headphone is, without a doubt, the Sennheiser HD6XX. This headphone is positioned at a price point where it doesn’t belong. You are getting a headphone that has the internals of one of the most celebrated headphones. 

There isn’t a lot that can stand up to the HD6XX’s sound quality and technical ability at this price point. Also, the lower price point enables you to have a more budget in getting a capable source that can fully drive the Sennheiser HD6XX. 

Better Performer: Sennheiser HD660S 

The Sennheiser HD660 S in holder

If you are looking for a superior-sounding headphone, then that is without a doubt the Sennheiser HD660S. Its technical performance is significantly better than the HD6XX. Everything from the bass to the imaging and soundstage is simply better. The Sennheiser HD660S can confidently go up against most of the modern headphones in its price point. 

If you have the right budget for this headphone, then the HD660S will give you the best performance out of all the HD600 Series headphones. 

Should You Upgrade to the HD660S? 

If you already own the HD6XX or the HD58X, then you might want to think twice about upgrading the HD660S. Despite outperforming the HD6XX in all categories, the overall sound and experience that you get will mostly be the same. If this is what you are looking for, then the HD660S will be a good upgrade.

However, if what you are looking for is a completely different sound signature, then you might want to audion other pairs first. If you are looking for a more analytical headphone, then the Sennheiser HD800S might be a better fit. 

If you are looking for a similar experience, then the Drop Aeon Flow X is also a good choice. And if you are looking for something completely different, then planar magnetic headphones such as the Audeze LCD 2C are a great choice. 

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