Note that this is a discontinued product. You may want to visit the brand's page here to browse their newer products.
What reviewers think
Bloggers and YouTubers have tried this product—so we've summarized their strongest opinions below. Links to full reviews follow.
Product Strengths
- A hard case is included, which is rare for headphones at this price point.
- The sound is brilliant, with accurate and balanced bass, never boosted over what’s present in the material.
- They are tremendously light and comfortable, suitable for all-day wear.
- The earcups are made of aluminum, and the adjustment mechanisms and headband core are also made out of lightweight metal, adding to the sturdy build.
- Offers advanced features such as dual entry, daisy chaining, and pass-through listening capability.
Product Considerations
- Treble can be a bit harsh at times, and higher mids can be crisp.
- The coiled cable is short, only about 4 feet when not stretched.
- A conservative tuned sub-bass may not be enough for bassy listeners.
- The flatish response may make lower vocals a bit laid back.
- Sub-bass may distort if pushed too much by an EQ.
Comparisons (according to reviewers)
- The Koss Pro4S destroys the Sony MDR-7506.
- The Pro4S is a slightly cooler-sounding companion to the AKG K371/K361.
- If listeners have found Beyerdynamic's DT models too harsh in the treble, but still enjoyed their overall character, then the Pro4S may be a favorite headphone.
- The DT-770 80 ohm still has a lot more bass than the Koss Pro 4S.
Takeaway: The Koss Pro4S is a comfortable and durable studio headphone with a balanced sound suitable for monitoring. With its special features and design, it is a capable choice for working professionals.
All
Pro4S Studio
reviews

Manufacturer details
- Frequency Response: 10-25,000 Hz
- Impedance: 35 Ohms
- Sensitivity: 99dB SPL
- Cable: Detachable 4ft/1.2m coiled cord
- Features: Dual Choice Entry
- Included Accessories: Hardshell case, 6.3mm adapter
Brand highlights
Taking a step back to look at reviewers' thoughts of the brand's entire lineup—not just this product—what stands out most is the following:
- Koss is known for electrostatic headphones and complete systems, including dedicated energizer/amplifiers, at a comparatively affordable price.
- The brand balances the retro aesthetic of classic designs with modern features such as wireless connectivity and detachable cables.
- The brand fosters a community around its products, evident in collaborations with companies such as Drop, and is receptive to community feedback in design and development.
Select products
Porta Pro
- Positioning: The entry-level design focused on portability and everyday use.
- Description: Features updated aesthetics with inline controls and a comfortable build that suit small-room or on-the-go listening. Compared to the mid-range and electrostatic models, it offers a simpler sound signature and basic functionality without high-end tuning.
PRO/4AA
- Positioning: A mid-range option aimed at users looking for robust, everyday performance.
- Description: Delivers clear sound and reliable build quality that make it suitable for studio work and extended listening sessions. When compared to the entry-level Porta Pro and more premium electrostatic products, it provides improved audio clarity and durability with a modest step up in cost.
QZ99
- Positioning: A balanced mid-range model designed for everyday versatility.
- Description: Introduces modern design elements and enhanced comfort to fit both home and travel use with stable sound performance. In comparison to the PRO/4AA and Porta Pro, it emphasizes design refinement and user experience, though it does not offer the advanced technology of the electrostatic series.
ESP950
- Positioning: A high-end electrostatic system aimed at detailed and precise sound reproduction.
- Description: Uses electrostatic driver technology to deliver clear, crisp audio with a spacious soundstage suitable for controlled listening environments. Compared to non-electrostatic models like the QZ99 and PRO/4AA, it stands out with higher sonic precision while remaining a step below the flagship model in overall refinement.
ESP95X-plus
- Positioning: The flagship model featuring premium electrostatic technology and superior build quality.
- Description: Refines electrostatic design with enhanced tuning and high-quality materials for exceptional clarity and performance. When contrasted with the ESP950 and other lower-tier models, it offers the most advanced features and detailed sound response.
Our take on the brand
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Product Strengths
- Exquisite build quality with premium materials, like anodized aluminum, memory foam, lambskin leather, and high-quality polymer
- Very comfortable, generously padded with memory foam wrapped in lambskin, and the headband distributes pressure evenly
- Long battery life, up to 35 hours with ANC on and 40 hours with ANC off
- Sound quality is rich, refined, spacious, balanced, and impressively detailed
- Good voice pickup and decent noise suppression in moderately noisy environments
- Connectivity options are available
Product Considerations
- Round ear pads may pull down on ear cartilage and rest on ear lobes
- The HX can only be laid down flat, they are not fully collapsible
- ANC is good, but not quite at the level of industry leaders
- Touch panel is awkward to use, and touches are often not registered properly
Comparisons (according to reviewers)
- Vs Sony 1000XM4/XM5 and Bose 700, ANC on the HX is not quite at the level of these industry leaders
- Vs the H95, the HX are more sensible, and noticeably cheaper
- Vs the Sony XM3, the HX looks far more refined
- Vs the Apple AirPods Max, the HX has up to 15 hours of additional battery life, and are also 100g lighter
- Vs the Bowers & Wilkins PX7, the HX brings a slightly higher level of refinement, showcasing detail and nuances that are missed
Takeaway: The Beoplay HX are beautifully made headphones that deliver excellent sound quality and are highly comfortable. If the user values aesthetics as much as audio and is willing to pay a premium for quality, then the HX is worth consideration.
Video review
Our take on the brand
Product Strengths
- Flame maple housings are crafted with precision and look premium, adding both durability and aesthetic value
- Delivers exceptional clarity with detailed highs and a balanced mid-range
- Lightweight and comfortable, making them easy to wear for extended periods
- Offers a fast, tight, clean, and well-separated sound signature with a colorful and multidimensional soundstage
- Easy to drive, making them suitable for use with various portable sources
Product Considerations
- Bass response may feel a little too neutral for some listeners who prefer more emphasis on the low end
- The low midrange is somewhat recessed, which might rob male vocalists of presence and richness
- The included soft case may not be sufficient for protecting the headphones
Comparisons (according to reviewers)
- Compared to Focal Stelia or Sennheiser HD800S, the ATH-WP900 excels in build quality and high-frequency clarity, but those alternatives might be better for bass enthusiasts
- The WP900 has a natural sense of detail and energy, similar to Grado mids, but unlike a Grado, it delivers a fun, thumping bass line
- Compared to the Sennheiser HD-660S or the Beyerdynamic DT-1990 Pro, those alternatives offer a bit more warmth and bass presence, albeit with different designs
Takeaway: The ATH-WP900 headphones are a great choice for audiophiles who value clarity and a unique aesthetic design. The build quality and easy portability make them a set of headphones that is fun to use.
Video review
Our take on the brand
Product Strengths
- Comfortable for extended wear, with reviewers sometimes forgetting they are wearing headphones
- Sound reproduction is transparent and reliable, providing an accurate monitoring experience
- Good at isolation, making it easier to identify unwanted sounds in recordings
- Excellent build quality and handsome design using aluminum
- Midrange accuracy is a strong point, potentially comparable to the HD600
Product Considerations
- The bass can be a little bloated
- Some find the earpads stiff and uncomfortable initially
- Treble may be a bit too recessed
- Cable microphonics can be an issue
Comparisons (according to reviewers)
- Compared to the Focal Allegias, the NDH 20 offers a more neutral tuning
- Compared to the Sennheiser HD 650, both models convey the midrange accuracy about the same, but the Sennheisers are lighter in the bass and a little brighter in the upper mid/treble area
Takeaway: The NDH 20 offers a combination of comfort, isolation, and accurate sound, making it a solid choice for studio use. It is a well-built and reliable tool for those needing a focused monitoring experience.
Video review
Our take on the brand
Product Strengths
- Good build quality and finish, with attention to detail and craftsmanship.
- Natural, organic, and well-balanced sound, with good detail.
- Spacious soundstage for a closed-back headphone.
- Very easy to drive and efficient, suitable for portable sources.
- Very good mid-range, with up-front vocals.
Product Considerations
- Treble can be a bit recessed or rolled-off.
- Burn-in time may be required before the sound settles.
- Can be critical of poor recording quality.
Comparisons (according to reviewers)
- Tone balance is as good as HiFiMan Aria, but more dynamic and better with female vocals.
- Wider soundstage than Focal Celesti.
- Audeze LCD2 is darker.
- More high mid than beyerdynamic DT1770 Pro.
Takeaway: The Magni headphones are well-built and comfortable, offering a natural and enjoyable sound, with a surprising soundstage for closed-back headphones. It is a great choice for someone who wants a well-rounded headphone without needing a powerful amplifier.
Video review
Our take on the brand
What competes at this price?
Our Summary
Product Strengths
- Shockingly good for the money, a very well-tuned headphone for the price category
- Good bass response that is fun, with lots of thumpiness and impact in the lower sub-bass regions, while maintaining a clean mid-bass region
- Trouble response is fairly target-adherent with a chill character and not overly fatiguing
- Comes with a banger accessories package providing two cables, a carry case, more than a lot of companies are coming out with
- Delivers impressive sound quality across the board, backed by excellent build quality and a generous set of accessories
Product Considerations
- The actual earpad area for the ear is not super great, and it will be felt a little bit on the ear, might be more on-ear than fully over-ear if you have really large ears
- Sound staging is one area that could improve the most, because there is almost none, can sound almost claustrophobic, because everything is happening right here all the time
- Mid-range is not all that exciting to listen to, vocals can be shouty or honk-type sound to certain vocalists
- Build quality feels good for $150, but it would not pass the sniff test for $500, definitely feels like it's a budget device
Comparisons (according to reviewers)
- The AKG K361 has advantages over the FiiO FT1, like sound staging
- The FT1’s level of midrange fidelity is impressive, rivaling the best mid-fi headphones such as the Sennheiser HD6XX and the Sundara
- It outshines most closed-back classics, including the Sony MDR-7506, AKG K361, and beyerdynamic DT700 Pro X
- The smaller FiiO FT1 was enjoyed even more than the FiiO FT5, since it strikes the right balance between fun, warmth, and technicality, handling tough tracks with much more ease than anticipated
Takeaway: The FiiO FT1 is a surprisingly good closed-back headphone for the money and offers a well-tuned sound signature with good bass response. This headphone is priced at $150 and is surprisingly nice with some great terminations.
Video review
Our take on the brand
Our Summary
Comparisons (according to reviewers)
- ANC does not compete with Sony or Bose, even in the same price category, let alone their higher-end stuff.
- The Sennheiser HD 450BT and the Urbanista Los Angeles offer better ANC or a unique solar charging design, respectively, for a small price increase.
- More comfortable than the Skullcandy Crusher ANC 2 and Apple AirPods Max thanks to plush padding.
- The Edifier WH950NB hybrid ANC is well implemented, making it a legitimate reason to consider, even outside of the big price savings, as the Stax SPIRIT S3 does not feature any noise cancellation.
Takeaway: The Edifier WH950NB is a comfortable and feature-rich headphone that offers good noise cancellation and balanced sound, making it a solid choice for commuters or anyone seeking an immersive listening experience. With its long battery life and customizable app, these headphones are a great value for the price.
Video review
Our take on the brand
Our Summary
Product Strengths
- Comfortable, with deep and wide ear pads that fit most ears and are made of compliant pleather
- Easy to drive, performing well even with simple sources like Apple dongles
- Good build quality, utilizing metal in the adjustment mechanism and steel-reinforced earcups
- Decent passive noise isolation for a closed-back headphone, blocking out more noise than open-back models
- Relatively wide and natural soundstage for a closed-back headphone
Product Considerations
- Can get warm after extended use (3-4 hours)
- Bass response can be inconsistent depending on head shape and seal, especially for those wearing glasses
- Treble response can be inconsistent, sometimes sounding dark or bright depending on the track
- Some reviewers found the sound signature to be a bit boxy, stale, or not as rich as other Sennheiser models
- The stock cable is fairly basic and a balanced cable is an optional purchase
Comparisons (according to reviewers)
- The HD 620S has better bass extension and imaging than the HD 600, but the HD 600 is more comfortable for some due to lower clamp force
- The HD 620S is built more substantially with a stainless steel reinforced headband and chunky ear pads than the HD 560S, though visually similar
- The HD 620S has a better tuning out of the box than the beyerdynamic DT770 Pro X, where the beyerdynamic benefits more from EQ, and is more comfortable
- The HD 620S provides better passive noise isolation than the HIFIMAN Sundara (closed back)
- The beyerdynamic DT 700 PRO X delivers more consistent sound between wears, whereas the HD 620S is negatively affected by wearing glasses
Takeaway: The Sennheiser HD 620S are comfortable and well-built closed-back headphones that offer a decent soundstage and are easy to drive, making them a good option for users needing isolation without sacrificing too much sound quality. The sound is generally enjoyable, especially for those who appreciate a balanced signature and Sennheiser's house sound.
Video review
Our take on the brand
Our Summary
Product Strengths
- Neutral and balanced sound profile makes it suitable for studio monitoring and critical listening
- Comfortable for extended use due to soft padding on the earcups and headband
- Sturdy and robust build quality uses metal in key areas
- Long battery life often exceeds the advertised 50 hours in tests
- USB-C charging and a quick charge feature, providing multiple hours of playback with a short charge, are also highlighted
- The Audio-Technica Connect app enables users to customize the sound profile using an equalizer and presets, adjust L/R balance, customize voice assistant preference, customize volume, and other settings
- Flexibility of both Bluetooth wireless and wired connectivity via a 3.5mm audio jack
- Multipoint pairing, allowing simultaneous connection to two devices, is also a valuable feature
Product Considerations
- Absence of ANC is a common point of concern
- While the headphones offer decent passive isolation due to their over-ear design, they do not block out noise as effectively as ANC-equipped alternatives
- Heat can build up after longer listening sessions
- The earcups can sometimes be backward when putting on the headphones
- Tight fit may be uncomfortable for users who wear glasses or have larger heads
- Inconsistent bass and treble delivery, and are sensitive to the fit, seal, and positioning of the headphones on the head
Comparisons (according to reviewers)
- Vs Bose QC35: The ATH-M50xBT2 has a slightly shorter battery life, but unlike the Bose, it lacks noise cancelling
- Vs Sennheiser HD450BT: The ATH-M50xBT2 has a slightly shorter battery life than the Sennheiser HD450BT, but unlike the Sennheiser, it lacks noise cancelling
- Vs Sony WH-1000XM4: The Sony WH-1000XM4 is more comfortable and well-built, and unlike the Audio-Technica, it features an ANC feature
- Vs Audio-Technica ATH-M50xBT: The ATH-M50xBT2 has a longer continuous battery life and better recording quality
- Vs Audio-Technica ATH-M50xBT: The ATH-M50xBT2 also features sound customization options and multi-device pairing
- Vs Anker Soundcore Life Q30 Wireless: The Anker Soundcore Life Q30 Wireless feature an ANC feature, unlike the Audio-Technica ATH-M50xBT2 Wireless
Takeaway: The ATH-M50xBT2 headphones are a solid choice for those seeking balanced sound, comfort, and versatility in both wireless and wired modes. These headphones are suitable for listening to music, working from home, or in the office.
Video review
Our take on the brand
Our Summary
Product Strengths
- Comfort is good and fit feels like the original Sundara.
- Very easy to drive with high sensitivity and low impedance.
- Build quality is good, and the beechwood earcups give a touch of quality and substance.
- Good bass extension and punch.
- Mid-range is relaxed, lush, airy, and offers a good level of details.
Product Considerations
- The sound signature is not equivalent or familiar to that of the open-back Sundara.
- Treble response is dark.
- Soundstage is average in size, and not very open sounding.
- Stock cable is not great, and a replacement may be desired.
- Some reviewers found the mid-range to be too mid-forward.
Comparisons (according to reviewers)
- Compared to the HiFiMan Sundara (Open-Back), the Closed-Back has different drivers, is tuned differently, and is not just a variation of the original open-back Sundara.
- Compared to the AKG K361, the AKG has better soundstaging and imaging.
- The Sundara Closed-Back is superior to the Hifiman HE400SE in terms of bass performance.
Takeaway: The Sundara Closed-Back headphones are comfortable and easy to power, and have a unique sound signature that some may find enjoyable. They are a good option to consider if one wants to try a closed-back planar headphone.
Video review
Our take on the brand
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