Audio T Verdict
The Sennheiser HD 620S tackle one of the oldest compromises in headphone design: getting the privacy and isolation of a closed-back headphone without making the presentation feel overly enclosed. They do a remarkably convincing job of bridging that gap.
The custom 42mm transducers, angled baffle and carefully controlled closed enclosure create a spacious and precise stereo image while the sealed earcups keep far more of the outside world at bay than an HD 600, HD 650 or HD 660S2. The result feels recognisably Sennheiser, with clear vocals, controlled bass and plenty of fine detail, but in a format that is much easier to use when other people are nearby.
At 150 ohms they deserve a decent headphone output, although they are not prohibitively difficult to drive. They also now have excellent upgrade potential through Sennheiser's optional 4.4mm balanced cable and HD 500 BAM microphone. If you love the idea of an open-back Sennheiser but your listening environment simply will not accommodate one, the HD 620S should be very high on the audition list.
Closed-Back, but Not Active Noise Cancelling
The HD 620S reduce surrounding noise through their sealed earcups and physical acoustic isolation. They do not contain electronic Active Noise Cancellation, Bluetooth or a rechargeable battery. They are traditional passive wired hi-fi headphones.
Sennheiser HD 620S Closed-Back Headphones
The Sennheiser HD 620S are closed-back around-ear headphones developed for listeners who want the natural tonal balance and spacious imaging associated with Sennheiser's open-back hi-fi models but need greater privacy and isolation.
They combine elements of Sennheiser's established HD 600 and HD 500 families. A custom-tuned 42mm dynamic transducer uses a 38mm diaphragm and ultra-light 150-ohm aluminium voice coil, while the driver is positioned on an unusually open angled baffle designed to recreate the broad stereo perspective normally associated with open headphones.
The rear of each enclosure is then carefully controlled by a steel plate rather than simply sealing the driver inside a conventional plastic cavity. This helps manage internal reflections while providing the isolation expected from a closed-back headphone.
- Closed-back around-ear hi-fi headphones
- Custom-tuned 42mm dynamic transducers
- 38mm diaphragm
- Transducers manufactured in Tullamore, Ireland
- Ultra-light aluminium voice coil
- 150-ohm nominal impedance
- Angled driver positioning
- Open acoustic baffle within closed enclosure
- Steel rear acoustic plate
- 6Hz to 30kHz frequency response
- 110dB SPL at 1V RMS
- Less than 0.05% THD
- Natural, spacious closed-back presentation
- Passive acoustic isolation
- Steel-reinforced earcup covers
- Steel-reinforced headband sliders
- Internally vented synthetic-leather earpads
- Detachable single-sided cable
- 1.8m cable supplied
- 3.5mm stereo connection
- 6.3mm screw-on adapter supplied
- Optional 4.4mm balanced cable compatibility
- Optional HD 500 BAM microphone compatibility
- Replaceable earpads and cables
- No battery, Bluetooth or ANC
Open Sound From a Closed Headphone
The basic challenge facing any closed-back headphone is that sealing the rear of the transducer changes the way sound behaves inside the earcup.
Reflections from that enclosed space can colour the sound, reduce the sense of openness and make the presentation feel more obviously contained inside the headphones.
Sennheiser designed the HD 620S specifically to tackle that problem rather than accepting it as an unavoidable characteristic of a closed headphone.
42mm Reference-Grade Transducer
The HD 620S use a custom-tuned 42mm dynamic transducer with a 38mm diaphragm.
The transducers are manufactured at Sennheiser's specialist facility in Tullamore, Ireland, and have been developed to retain the smooth tonal character associated with the company's established open-back hi-fi models.
38mm Diaphragm
The diaphragm is the moving surface responsible for converting the electrical signal into sound.
Its relationship with the voice coil, magnet, acoustic loading and earcup has a major influence on transient response, distortion and tonal balance.
In the HD 620S, Sennheiser combines the 38mm diaphragm with a lightweight aluminium voice coil and carefully controlled closed enclosure.
150-Ohm Aluminium Voice Coil
The ultra-light aluminium voice coil has a nominal impedance of 150 ohms.
Sennheiser uses a high damping factor to maintain control of the moving assembly, helping reproduce fast transients and the decay of instruments cleanly rather than allowing bass notes or other sounds to linger longer than intended.
Why 150 Ohms?
A 150-ohm headphone sits in an interesting middle ground.
It is considerably higher in impedance than everyday portable headphones, but only half the nominal impedance of classic 300-ohm Sennheiser models such as the HD 600 and HD 650.
This makes the HD 620S practical with a wider range of capable headphone outputs while still benefiting from good amplification.
Do I Need a Headphone Amplifier?
Not necessarily simply to make the HD 620S work, but they are revealing 150-ohm hi-fi headphones and deserve a decent headphone output. A capable integrated amplifier, DAC/headphone amplifier or dedicated headphone amp can provide greater voltage headroom, control and dynamic performance.
110dB SPL Sensitivity
Sennheiser specifies a sound pressure level of 110dB at 1V RMS.
Taken together with the 150-ohm impedance, this means the HD 620S are less intimidating to drive than the impedance figure might suggest.
The quality of the source still matters, particularly if you want the headphones to retain control and dynamic headroom on more demanding recordings.
Less Than 0.05% Distortion
Total harmonic distortion is specified below 0.05% at 1kHz and 90dB SPL.
Keeping unwanted distortion low helps preserve the subtle differences between instruments, voices and recording spaces rather than masking them with additional harmonic information generated by the headphones themselves.
Angled Transducer Positioning
The HD 620S transducers are angled towards the ears rather than sitting completely flat against the sides of the listener's head.
This geometry helps recreate the directional relationship of a conventional pair of loudspeakers positioned in front of the listener.
It contributes to:
- Wider stereo imaging
- Clearer left-to-right positioning
- Greater sense of depth
- Better separation between performers
- More precise positional information
A Remarkably Open Baffle
Although the earcups themselves are closed, the transducer operates on a deliberately open internal baffle.
This encourages freer movement of air around the driver and helps reduce the confined presentation that can occur with more conventional sealed headphones.
The intention is not to make the HD 620S sound identical to an open model, but to retain more of the spatial behaviour listeners associate with open headphones.
Steel Rear Acoustic Plate
A steel plate closes the rear acoustic volume.
This is not simply decorative reinforcement. Sennheiser uses the metal structure as part of the acoustic design to manage internal reflections and improve isolation.
Controlling those reflections helps prevent the enclosure itself from obscuring fine detail.
Steel-Reinforced Earcup Covers
The external earcup covers also incorporate steel reinforcement.
Alongside the acoustic benefits of the rear plate, the metal construction provides additional rigidity and durability compared with relying entirely on lightweight moulded plastic.
Steel-Reinforced Headband Sliders
The adjustable headband mechanism is reinforced with steel as well.
This is particularly useful on headphones intended for long-term ownership because the headband adjustment points experience repeated mechanical stress every time the headphones are put on, removed or resized.
6Hz to 30kHz Frequency Response
Sennheiser specifies the HD 620S from 6Hz to 30kHz.
The extended low-frequency specification reflects the model's ability to reproduce genuinely deep bass rather than creating the impression of weight solely through an exaggerated mid-bass response.
Deep but Articulate Bass
One advantage of closed-back construction is the ability to maintain low-frequency pressure around the ear.
The HD 620S take advantage of that while aiming to avoid the overblown bass character sometimes associated with sealed headphones.
Low frequencies should provide weight and impact while retaining enough definition to distinguish:
- Individual bass-guitar notes
- Kick-drum texture
- Low synthesiser lines
- Orchestral percussion
- Double bass
- Film-score effects
Natural Midrange
Sennheiser specifically positions the HD 620S around the natural tonal qualities associated with its HD 600 family.
That makes voices, guitars, piano and acoustic instruments particularly important to the tuning rather than treating the midrange merely as the space between impressive bass and treble.
Detailed Without Excessive Brightness
The HD 620S are intended to reveal fine information while avoiding a deliberately aggressive treble balance.
This helps preserve details such as cymbal decay, room reverberation, string texture and vocal articulation without requiring the headphones to constantly draw attention to the upper frequencies.
Passive Acoustic Isolation
The closed earcups substantially reduce interaction with the surrounding room compared with an open HD 600-series headphone.
This can be especially useful when listening:
- In a shared living room
- In a home office
- Near other family members
- Where background conversation is present
- At a desk
- During gaming
- When recording or editing audio
Less Sound Leakage
The same closed design also keeps considerably more of your music inside the earcups.
This is one of the HD 620S's biggest practical advantages over an HD 600, HD 650 or HD 660S2 if somebody else is sitting in the same room.
Not the Same as ANC
Passive isolation works by physically reducing the amount of external sound reaching the ear.
Active Noise Cancellation instead uses microphones, electronics and an opposing audio signal to reduce certain external sounds.
The HD 620S use the first approach only. There is no ANC circuitry altering the signal and no battery required.
Internally Vented Earpads
The synthetic-leather earpads incorporate internal ventilation.
The aim is to maintain the acoustic seal required by a closed headphone while making long listening sessions more comfortable than they might be with a completely unvented cushion.
Synthetic-Leather Earpads
Sennheiser specifies artificial leather on a polyurethane basis for the HD 620S ear cushions.
The material helps form the acoustic seal around the listener's ears, which is important both for isolation and for maintaining consistent bass performance.
Replaceable Earpads
Genuine replacement HD 620S earpads remain available separately.
Earpads naturally compress and wear over time, and on a closed headphone their condition can have a particularly significant influence on the acoustic seal.
Being able to replace them helps extend both the physical and acoustic life of the headphones.
Detachable 1.8m Cable
The supplied cable measures approximately 1.8 metres and connects to one earcup using Sennheiser's twist-lock system.
At the source end is a conventional 3.5mm stereo plug, providing straightforward compatibility with many current headphone amplifiers, DACs and audio interfaces.
6.3mm Adapter Included
A screw-on adapter converts the standard 3.5mm connection to a full-sized 6.3mm plug.
This allows the same supplied cable to connect directly to:
- Integrated amplifiers
- Dedicated headphone amplifiers
- DAC/headphone amplifiers
- AV receivers
- Professional audio interfaces
Twist-Lock Headphone Connection
The headphone-side cable connection uses Sennheiser's established 2.5mm twist-lock arrangement.
This keeps the plug secure during normal use while still allowing the cable to be removed, replaced or upgraded when required.
Optional 4.4mm Balanced Cable
Sennheiser offers a dedicated 1.8m balanced HD 500-series cable that is officially compatible with the HD 620S.
The cable terminates in a 4.4mm Pentaconn plug for suitable headphone amplifiers and portable audio equipment.
Will a Balanced Cable Automatically Sound Better?
Not necessarily. A balanced connection can be useful where a particular headphone amplifier provides its best performance or greater output through the balanced socket, but the amplifier design matters more than simply changing the plug. Choose the connection that best suits the equipment you are using.
Optional HD 500 BAM Microphone
The HD 620S are also officially compatible with Sennheiser's HD 500 BAM boom-arm microphone.
The standard cable is removed and the microphone assembly twists directly into the headphone connection, turning the HD 620S into a high-quality wired headset.
10mm Condenser Boom Microphone
The HD 500 BAM uses a dedicated 10mm condenser microphone with a cardioid pickup pattern.
The directional design places greater emphasis on the voice in front of the microphone while reducing surrounding noise compared with an omnidirectional inline microphone.
Inline Volume and Mute Controls
The HD 500 BAM cable incorporates both headphone-volume adjustment and microphone mute controls.
This gives the HD 620S a useful second role for gaming, online communication and remote work without permanently converting the headphones into a headset.
Useful for Gaming
The HD 620S are particularly interesting for gaming because they combine closed-back isolation with unusually spacious stereo imaging.
Accurate positional information can help with:
- Footstep location
- Movement around the player
- Environmental effects
- Directional dialogue
- Large cinematic soundtracks
The passive wired connection also eliminates the Bluetooth audio latency associated with some wireless gaming headsets.
Useful for Working From Home
The isolation provided by the closed earcups can reduce surrounding distractions when working at a desk.
Add the optional HD 500 BAM and the same headphones can then handle music, video calls and online meetings without maintaining a separate communications headset.
Useful for Amateur Music Production
Sennheiser also positions the HD 620S for music-production and editing applications.
The closed construction is useful where microphone spill or surrounding noise would make an open headphone less practical, while the relatively natural tonal balance and spatial presentation can help when checking recordings and mixes.
They remain consumer hi-fi headphones rather than a dedicated professional monitoring model, but their character makes them useful for analytical work as well as ordinary listening.
Useful for Film and Television
The wide stereo presentation works particularly well with film soundtracks, where dialogue, effects and music can occupy clearly different positions within the image.
The extended bass response also gives action scenes and film scores greater weight without needing electronic bass enhancement.
HD 620S or HD 569?
HD 620S
- Closed-back
- 42mm driver assembly
- 38mm diaphragm
- 150-ohm impedance
- 6Hz to 30kHz response
- 110dB SPL at 1V
- Less than 0.05% THD
- Custom Irish-made transducers
- Steel rear acoustic plate
- Reference-oriented tuning
- Strong focus on spacious closed-back imaging
- 1.8m cable
- Optional balanced cable
- HD 500 BAM compatible
HD 569
- Closed-back
- 38mm dynamic drivers
- 23-ohm impedance
- 10Hz to 28kHz response
- 115dB SPL at 1V
- Less than 0.2% THD
- E.A.R. angled acoustics
- Much easier load for portable equipment
- Two cables supplied
- Inline microphone cable supplied
- Practical everyday listening focus
- HD 500 BAM compatible
Which Should You Choose?
The HD 569 remain the more straightforward choice if easy source compatibility, two supplied cables and everyday versatility matter most.
The HD 620S are a substantial step towards serious reference listening, with lower distortion, a more sophisticated acoustic enclosure and greater emphasis on reproducing the spacious character normally associated with an open headphone.
HD 620S or HD 600?
HD 620S
- Closed-back
- 42mm driver assembly
- 38mm diaphragm
- 150-ohm impedance
- 6Hz to 30kHz response
- 110dB SPL at 1V
- Passive acoustic isolation
- Much lower sound leakage
- Strong, controlled low bass
- 1.8m cable
- 3.5mm connection
- Optional 4.4mm balanced cable
HD 600
- Fully open-back
- 42mm driver assembly
- 38mm diaphragm
- 300-ohm impedance
- 12Hz to 40.5kHz response
- 97dB SPL at 1V
- Virtually no acoustic isolation
- Considerably greater sound leakage
- Classic neutral reference presentation
- 3m cable
- Designed primarily for quiet listening spaces
Closed or Open?
The HD 600 remain the obvious choice if you have a completely quiet listening environment and want the openness of a traditional reference headphone.
The HD 620S become compelling when the real world gets in the way. They allow much more private listening and reduce outside distractions without abandoning the natural tonal qualities for which Sennheiser's reference headphones are known.
HD 620S or HD 660S2?
The HD 660S2 sit further up the open-back HD 600 hierarchy and use a 300-ohm platform with extended sub-bass and a warm, highly refined presentation.
The HD 620S are not simply a closed HD 660S2. They use a different 150-ohm transducer and acoustic enclosure designed around isolation and spatial performance within a closed cabinet.
If you can listen without disturbing anybody and outside noise is not a problem, the HD 660S2 provide the full open-back experience. If privacy matters, the HD 620S offer a far more practical alternative.
Built for Long-Term Ownership
The HD 620S contain no batteries, wireless radios or integrated digital electronics.
There is therefore no rechargeable cell whose eventual deterioration determines the useful life of the headphones.
Replaceable earpads and cables further support long-term ownership.
No Bluetooth, Apps or Firmware
The HD 620S are entirely passive.
There is no pairing process, Bluetooth codec, software application or firmware update standing between the source and the transducers.
The final performance is determined by the recording, headphones and equipment driving them.
Who Are the Sennheiser HD 620S For?
- Listeners wanting serious closed-back hi-fi headphones
- Sennheiser HD 600-series fans who need isolation
- People who cannot use open headphones in their listening environment
- Shared living rooms
- Home offices
- Desktop DAC and headphone-amplifier systems
- Integrated amplifiers with good headphone outputs
- Listeners wanting natural vocals and detailed sound
- Film and television listening
- Gaming
- Amateur recording and music production
- Listeners wanting optional balanced connectivity
- Users wanting optional boom-microphone support
- People looking for replaceable pads and cables
Who Are They Not For?
- Listeners specifically wanting a fully open-back presentation
- Customers wanting Bluetooth
- People wanting Active Noise Cancellation
- Customers wanting a microphone supplied as standard
- People looking for compact folding travel headphones
- Listeners who need the strongest possible aircraft-style noise cancellation
- Very low-powered sources unable to drive 150-ohm headphones adequately
Key Features
- Sennheiser HD 620S
- Article number 700401
- Closed-back hi-fi headphones
- Around-ear / circumaural fit
- Dynamic transducer principle
- Custom-tuned 42mm transducer
- 38mm diaphragm
- Transducers made in Tullamore, Ireland
- Ultra-light aluminium voice coil
- 150-ohm nominal impedance
- Angled transducers
- Open internal acoustic baffle
- Steel rear acoustic plate
- Steel-reinforced earcup covers
- Steel-reinforced headband sliders
- 6Hz to 30kHz frequency response
- 110dB SPL at 1V RMS
- Less than 0.05% THD
- Wide closed-back soundstage
- Passive acoustic isolation
- Reduced sound leakage
- Synthetic-leather earpads
- Internally vented earpads
- Replaceable earpads
- Detachable single-sided cable
- 1.8m supplied cable
- 3.5mm stereo plug
- 6.3mm adapter supplied
- HD 500-series twist-lock connection
- Optional 4.4mm balanced cable
- Optional HD 500 BAM microphone
- Replaceable cable
- No Bluetooth
- No battery
- No Active Noise Cancellation
- No app required
- 24-month manufacturer's warranty
Frequently Asked Questions
Are the Sennheiser HD 620S still current?
Yes. The HD 620S remain part of Sennheiser's current wired, HD Series, closed-back and audiophile headphone ranges.
Are the HD 620S open or closed-back?
They are closed-back headphones.
Why do Sennheiser describe them as having open sound?
The headphones use angled transducers, a deliberately open internal baffle and carefully controlled rear acoustic volume to create a wider and more spacious presentation than many conventional closed headphones.
Do the HD 620S block outside noise?
The closed earcups provide useful passive acoustic isolation.
Do they have Active Noise Cancellation?
No. There is no electronic ANC system.
Do they leak sound?
Far less than an open-back headphone, although no conventional headphone is completely silent to somebody sitting immediately beside you at high listening levels.
What size drivers do they use?
The HD 620S use a 42mm transducer assembly with a 38mm diaphragm.
Where are the transducers made?
Sennheiser manufactures the custom HD 620S transducers at its facility in Tullamore, Ireland.
Are the drivers angled?
Yes. Their positioning is designed to create a more loudspeaker-like stereo image.
What is the frequency response?
6Hz to 30kHz.
What impedance are the HD 620S?
150 ohms.
How sensitive are they?
Sennheiser specifies 110dB SPL at 1V RMS.
What is the THD?
Total harmonic distortion is specified below 0.05% at 1kHz and 90dB SPL.
Do I need a headphone amplifier?
Not necessarily, but the HD 620S are revealing 150-ohm headphones and benefit from a capable headphone output with sufficient voltage and headroom.
Can I use them with an integrated amplifier?
Yes, provided the amplifier has a suitable headphone output.
Can I use them with a computer?
Yes, through a suitable headphone output, audio interface or external DAC/headphone amplifier capable of driving 150-ohm headphones.
Can I use them with a phone?
Potentially, although many phones require an external USB-C or Lightning headphone DAC and their output capability varies considerably.
What cable is supplied?
A detachable 1.8m cable terminating in a 3.5mm stereo plug.
Is a 6.3mm adapter included?
Yes.
Is the cable detachable?
Yes. It uses Sennheiser's twist-lock headphone connection.
Can I use a balanced cable?
Yes. Sennheiser offers an optional 1.8m HD 500-series balanced cable with a 4.4mm source connector that is officially compatible with the HD 620S.
Will a balanced cable automatically improve the sound?
No. Its benefit depends on the design of the headphone amplifier. Balanced output can be useful where a particular amplifier performs best or provides greater output through that connection.
Can the earpads be replaced?
Yes. Genuine replacement HD 620S earpads are available.
What are the earpads made from?
Sennheiser specifies artificial leather on a polyurethane basis.
Are the earpads vented?
Yes. Sennheiser describes the pads as internally vented.
Do the HD 620S have a microphone?
No microphone is supplied as standard.
Can I add a microphone?
Yes. The optional Sennheiser HD 500 BAM is specifically compatible with the HD 620S.
What microphone does the HD 500 BAM use?
It uses a 10mm cardioid condenser microphone and includes inline volume and microphone-mute controls.
Are the HD 620S good for gaming?
Yes. Their closed-back isolation, spacious stereo image and wired connection make them particularly useful for gaming, and the optional HD 500 BAM adds dedicated microphone functionality.
Are they suitable for music production?
They can be useful for recording, editing and analytical listening where a closed headphone is needed, although they are sold as hi-fi headphones rather than a dedicated professional studio-monitoring model.
Are the HD 620S good for films?
Yes. Their wide stereo presentation, deep bass and isolation suit film and television listening particularly well.
What is the difference between HD 620S and HD 569?
Both are closed-back, but the HD 620S use a more sophisticated 150-ohm reference-oriented transducer and enclosure with considerably lower specified distortion and a stronger emphasis on spacious hi-fi performance. The HD 569 are easier to drive and include two cables, including one with a microphone.
What is the difference between HD 620S and HD 600?
The HD 600 are fully open 300-ohm reference headphones, while the HD 620S are closed 150-ohm headphones designed to provide much better isolation while retaining a natural, spacious presentation.
What is the difference between HD 620S and HD 660S2?
The HD 660S2 are premium 300-ohm open-back headphones with a different transducer and extended sub-bass tuning. The HD 620S prioritise isolation and lower sound leakage while recreating as much open-back spaciousness as possible from a closed enclosure.
Do they have Bluetooth?
No.
Do they need charging?
No. They contain no battery.
Do they require an app?
No.
How long is the manufacturer's warranty?
The HD 620S fall within Sennheiser's current 24-month consumer warranty category, subject to the applicable warranty terms and proof of purchase.
What comes in the box?
Sennheiser's current UK package specification lists the HD 620S headphones, a 1.8m cable with 3.5mm plug and a 3.5mm to 6.3mm adapter.
Related Sennheiser Products and Audio T Guides
Why Buy the Sennheiser HD 620S From Audio T?
The HD 620S sit in an unusual position between traditional closed-back headphones and Sennheiser's open-back reference models, so hearing them alongside the alternatives can be particularly useful. Audio T can help you compare them with the HD 569, HD 600, HD 650 and HD 660S2 and decide how much isolation you actually need.
We can also advise on headphone amplifiers, DACs, 150-ohm system matching, the optional 4.4mm balanced cable and the HD 500 BAM microphone if you want to use the HD 620S for gaming or calls as well as music.
- Friendly headphone advice
- Open and closed-back comparisons
- HD 600-series guidance
- HD 620S and HD 660S2 comparisons
- Headphone amplifier matching
- DAC and headphone amplifier advice
- 150-ohm headphone guidance
- 4.4mm balanced cable advice
- HD 500 BAM compatibility guidance
- Replacement cable and earpad advice
- Headphone demonstrations where available
- Ongoing after-sales support
Contact your local Audio T store if you would like to arrange a demonstration or discuss whether the Sennheiser HD 620S are the right headphones for your system and listening environment.