Description
The Sennheiser HD 660S 2 headphones take the performance of its predecessors, the HD 650 and HD 600, to the next level with its supernatural speed and effortless instrument reproduction, even to the ends of the frequency range. The natural, warm sound and extended sub-bass make it an ideal choice for audiophiles.
Enjoy the Sennheiser Sound
By using a brand-new transducer and a specially ventilated driver unit, the Sennheiser HD 660S 2 headphones are able to provide audiophiles with a sound that’s perfectly suited for reproducing complex and intricate recordings with confidence. It’s sharp, and detailed and maintains the engaging and dynamic qualities that make music enjoyable. The 38mm diaphragm is agile thanks to the aluminium voice coil, allowing for precise tonal and spatial characteristics to be communicated through ultra-quick fidelity.Meshes with Your Music
The HD 660S 2 has a steel mesh that’s impressive in design and performance. It completes the ventilated driver, which controls the air displacement consistently to minimise turbulence. Consequently, the diaphragm moves freely, allowing the music to be heard in its purest form, with a perfect balance of authenticity and expression. The steel composition enables much tighter production tolerances, resulting in consistent characteristics of every headphone produced. When combined with the open-back earcups, the sound produced by each transducer is unrestricted, mimicking the natural soundstage.Matched for Perfection
Each unit of the Sennheiser HD 660S 2 has undergone a matching process to pair the transducer with its counterpart on the opposite channel. These processes have very precise tolerances, and when combined with automated assembly, they ensure top-notch quality throughout.
Designed For Durability & Acoustics
The materials used to design the HD 660S 2 are lightweight and carefully chosen to not affect the acoustics of the system, while still maintaining the durability needed for daily, extended use.Connect to Any Source
The HD 660S 2 comes with multiple 9.8 feet /3m-long cables in the box. The ¼-inch / 6.3mm stereo connector is the standard plug for audiophiles and can be used with various devices such as headphone amplifiers, A/V receivers, digital audio players, and more. The 4.4mm balanced connector is designed for newer balanced output devices such as headphone amplifiers and digital audio players and provides a more stable connection over time.Transducer principle: dynamic, open
Transducer size: 38 mm
Frequency response: 8 – 41,500 Hz
Impedance: 300 Ω
Sound pressure level (SPL): 104 dB (1 kHz, 1 Vrms)
Total harmonic distortion (THD): <0.04% (1 kHz, 100 dB)
Ear coupling: Over-Ear
Weight: 260g
Adapter: 6.3 mm (1⁄4 inch) to 3.5 mm
Connector: 6.3 mm (1⁄4 inch) jack plug, 4.4 mm balanced plug
Cable length: 1.8m
Country of origin: Ireland
Magnetic field: 4.5mT
What's included
HD 660S2 headphones
6.3 mm cable (1.8 m), 4.4 mm cable (1.8 m)
6.3mm to 3.5mm adapter
Carry pouch
Warranty Period: 2 Years from the date of Invoice
Covered: Manufacturing Defects Only
Website: https://en-in.sennheiser.com/service-support-contact-service-centers-in-india
Contact No: 1800 22 36 32
Email Id: in-info@sennheiser.com
Sennheiser is a well-known brand in the audio industry. They offer a wide range of products catering to both audiophiles and casual listeners. Their products include open back and closed back audiophile headphones, in-ear monitors, ANC headphones, and true wireless earbuds. They are known for their exceptional sound quality and durability. Whether you're a professional musician or just a music enthusiast, Sennheiser has something for everyone.
H660S2 is very well built transducer, it's quite clampy out of the box. The clamps can be eased but stretch softly over the metal band on both side.
Sound: music is warm with mids forward. Spiciness in the treble is not noticed. Bass is also subdued.
Note: My previous headphone are 560s, Sundara, Eligia and Clears.
Comparison:
With 560s: the 560s is v shaped compared to 660s2. Mids/vocals sound so good on 660s2. But the sub bass, mid bass, highs sound bit better on 560s. 660s2 suits clasical music while 560s suits rock, electronic and pop music. 560s also tend to distort with volume and eq, 660s2 doesn't sweat with volume and eq.
With focal clear: the focal clear is best in all genre no competition but vocals are slightly prefered on 660s2
With Sundara: Sundara sound very thin when compared but excels in details and soundstage.
Overall 660S2 or any of the 6X0 series headset are must for audiophiles. This headset sings with right vocal based tracks.

Sounds very enjoyable and open and also has good imaging and instrument separation and definition to the various components of music is great. More clarity than HD 650 and also warmer but crispy sounding. I have the ifi zen stack but I like it more with just the zen dac v2 balanced output. Great headphone under 30k if you like warm sound with vocal intimacy and details of instruments.
You will enjoy the music as these sound good but little tight fit heavy when compared to competition like Sony MDR MV1 (which I owned already) . It's good looking when we compare it to Sony ones but only problem for me is it's tight fitting and I found little heavy for long listening, I can't bear these or even sony more then 40 mintues max in one go. Price could also be little better. But it's worthy one if you want to enjoy music at its best at stage live performance rather then in your head like closed back. One of the best ones in open back but again little tight fit and heavy for me.
Thank you for your review of the Sennheiser HD 660S2 Open Back Headphones. We appreciate your feedback and are glad to hear that you are enjoying the sound quality. We apologize for any discomfort caused by the tight fit and weight of the headphones. Thank you for choosing Sennheiser, The Audio Store and happy listening!

Description
The Sennheiser HD 660S 2 headphones take the performance of its predecessors, the HD 650 and HD 600, to the next level with its supernatural speed and effortless instrument reproduction, even to the ends of the frequency range. The natural, warm sound and extended sub-bass make it an ideal choice for audiophiles.
Enjoy the Sennheiser Sound
By using a brand-new transducer and a specially ventilated driver unit, the Sennheiser HD 660S 2 headphones are able to provide audiophiles with a sound that’s perfectly suited for reproducing complex and intricate recordings with confidence. It’s sharp, and detailed and maintains the engaging and dynamic qualities that make music enjoyable. The 38mm diaphragm is agile thanks to the aluminium voice coil, allowing for precise tonal and spatial characteristics to be communicated through ultra-quick fidelity.Meshes with Your Music
The HD 660S 2 has a steel mesh that’s impressive in design and performance. It completes the ventilated driver, which controls the air displacement consistently to minimise turbulence. Consequently, the diaphragm moves freely, allowing the music to be heard in its purest form, with a perfect balance of authenticity and expression. The steel composition enables much tighter production tolerances, resulting in consistent characteristics of every headphone produced. When combined with the open-back earcups, the sound produced by each transducer is unrestricted, mimicking the natural soundstage.Matched for Perfection
Each unit of the Sennheiser HD 660S 2 has undergone a matching process to pair the transducer with its counterpart on the opposite channel. These processes have very precise tolerances, and when combined with automated assembly, they ensure top-notch quality throughout.
Designed For Durability & Acoustics
The materials used to design the HD 660S 2 are lightweight and carefully chosen to not affect the acoustics of the system, while still maintaining the durability needed for daily, extended use.Connect to Any Source
The HD 660S 2 comes with multiple 9.8 feet /3m-long cables in the box. The ¼-inch / 6.3mm stereo connector is the standard plug for audiophiles and can be used with various devices such as headphone amplifiers, A/V receivers, digital audio players, and more. The 4.4mm balanced connector is designed for newer balanced output devices such as headphone amplifiers and digital audio players and provides a more stable connection over time.Transducer principle: dynamic, open
Transducer size: 38 mm
Frequency response: 8 – 41,500 Hz
Impedance: 300 Ω
Sound pressure level (SPL): 104 dB (1 kHz, 1 Vrms)
Total harmonic distortion (THD): <0.04% (1 kHz, 100 dB)
Ear coupling: Over-Ear
Weight: 260g
Adapter: 6.3 mm (1⁄4 inch) to 3.5 mm
Connector: 6.3 mm (1⁄4 inch) jack plug, 4.4 mm balanced plug
Cable length: 1.8m
Country of origin: Ireland
Magnetic field: 4.5mT
What's included
HD 660S2 headphones
6.3 mm cable (1.8 m), 4.4 mm cable (1.8 m)
6.3mm to 3.5mm adapter
Carry pouch
Warranty Period: 2 Years from the date of Invoice
Covered: Manufacturing Defects Only
Website: https://en-in.sennheiser.com/service-support-contact-service-centers-in-india
Contact No: 1800 22 36 32
Email Id: in-info@sennheiser.com
Sennheiser is a well-known brand in the audio industry. They offer a wide range of products catering to both audiophiles and casual listeners. Their products include open back and closed back audiophile headphones, in-ear monitors, ANC headphones, and true wireless earbuds. They are known for their exceptional sound quality and durability. Whether you're a professional musician or just a music enthusiast, Sennheiser has something for everyone.
H660S2 is very well built transducer, it's quite clampy out of the box. The clamps can be eased but stretch softly over the metal band on both side.
Sound: music is warm with mids forward. Spiciness in the treble is not noticed. Bass is also subdued.
Note: My previous headphone are 560s, Sundara, Eligia and Clears.
Comparison:
With 560s: the 560s is v shaped compared to 660s2. Mids/vocals sound so good on 660s2. But the sub bass, mid bass, highs sound bit better on 560s. 660s2 suits clasical music while 560s suits rock, electronic and pop music. 560s also tend to distort with volume and eq, 660s2 doesn't sweat with volume and eq.
With focal clear: the focal clear is best in all genre no competition but vocals are slightly prefered on 660s2
With Sundara: Sundara sound very thin when compared but excels in details and soundstage.
Overall 660S2 or any of the 6X0 series headset are must for audiophiles. This headset sings with right vocal based tracks.

Sounds very enjoyable and open and also has good imaging and instrument separation and definition to the various components of music is great. More clarity than HD 650 and also warmer but crispy sounding. I have the ifi zen stack but I like it more with just the zen dac v2 balanced output. Great headphone under 30k if you like warm sound with vocal intimacy and details of instruments.
You will enjoy the music as these sound good but little tight fit heavy when compared to competition like Sony MDR MV1 (which I owned already) . It's good looking when we compare it to Sony ones but only problem for me is it's tight fitting and I found little heavy for long listening, I can't bear these or even sony more then 40 mintues max in one go. Price could also be little better. But it's worthy one if you want to enjoy music at its best at stage live performance rather then in your head like closed back. One of the best ones in open back but again little tight fit and heavy for me.
Thank you for your review of the Sennheiser HD 660S2 Open Back Headphones. We appreciate your feedback and are glad to hear that you are enjoying the sound quality. We apologize for any discomfort caused by the tight fit and weight of the headphones. Thank you for choosing Sennheiser, The Audio Store and happy listening!
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The carry case is spacious enough for keeping one IEM and one small portable DAC with cable. Like I have kept Muse M4 dac with dihifi cable and one IEM in it. And the shell is hard so no chance of anything happening to the IEMs.
Was the cheapest option for a replacement cable I could find anywhere. And it works flawlessly too, no complaints
Amazing product
I recently purchased the Castor Pro KC earphones, and they have exceeded my expectations. The bass is deep and punchy, yet it doesn't overpower the mids and highs, ensuring excellent instrument separation. The tuning switches offer great flexibility, allowing me to customize the sound signature to my preference. Build quality is solid, and they are comfortable for long listening sessions. Overall, these IEMs deliver an impressive audio experience at their price point!

Very good cable
Works with 0.78mm 2pin iems
Using LG g8x thinq and output is higher than the smartphone's 3.5mm output.
Moondrop Link app works well, except a few buggy connectivity issues.
Good to see that one can create any Eq profile and save it in the app as long as it's done within the parameters. Very well executed.
KZ Castor Harman Target Version – Review
Design & Comfort
Lightweight, durable, and comfortable with a detachable cable. The in-line mic is useful for calls and gaming.
Sound Quality
Bass: Punchy and deep without overpowering.
Mids: Clear vocals and instruments.
Highs: Crisp but slightly bright.
Soundstage: Decent separation for immersive listening.
Pros:
✔ Enhanced bass
✔ Balanced tuning
✔ Comfortable & durable
✔ Affordable
Verdict:
A budget-friendly IEM with great sound and comfort, though the mic is just decent.
I'm using first time DAC most of the people refer this varient, difference between 3.5mm jac and this DAC D07 is absolutely awesome, so much details in hearing a song and music, loved it ❤️❤️❤️❤️👌👌👌🙏🙏🙏
Solid pouch
With good space
The product is worth the money
And I personally love the your faster delivery service
I got the product just in with 30 Hrs

I like Moondrop ECHO-A Dac. It is not powerful Dac but it produces quality sound .

Great for listening to all music genres, gaming on PC or consoles or pretty much any thing you'd like to do with a pair of earphones.
Superb packaging 👍🏻 delivered what was promised.

I recently got my hands on the ROSESELSA AURORA Ultra IEM, and I must say, it has exceeded my expectations! For under 2,000 INR, this IEM delivers exceptional value and performance that can easily compete with many pricier models out there.
What really stands out to me is its versatility. The AURORA shines across all genres, whether I'm diving into classical symphonies, jamming to rock anthems, or vibing with electronic beats. The sound quality is simply fantastic, making every listening session a joy.
A cherry on top is the comfort factor—these IEMs are small and lightweight, so they don’t cause any discomfort during long listening sessions. If you’ve had issues with larger IEM shells in the past, you’ll find the AURORA to be a perfect fit. Plus, the cable quality is impressive for the price, adding to the overall value of this product.
To unlock the full potential of these IEMs, I highly recommend investing in an external dongle. I personally use the Kiwi Ear Allegro Mini DAC, and it has truly elevated my audio experience. If you're on the hunt for a budget-friendly IEM that doesn’t compromise on sound quality, the ROSESELSA AURORA is a must-try!
I also want to take a moment to thank the audio store for their outstanding service. My order arrived in perfect condition, and their customer support team was incredibly friendly and helpful. Overall, this has been a wonderful experience, and I’m absolutely thrilled with my purchase!
As a v16 owner this is a worthy upgrade .
Fit :
The iem is designed aesthetically that it fits like custom made
Sound impressions :
Treble is perfectly done with being sibilant, Mids sounds very organic and clear, Bass is the best part here it's a step up from their previous flagship v16.
Staging is better and so is the resolution, A total flagship level iem which punches above the price tag
Thanks to Pritam for his exceptional customer service and deal .
Definitely recommended

Have a great features and I am very happy after buying this m71 thanks audio store 🙏🙏