Koss Pro4S – Review

Koss Pro4S

Koss Pro4S

| Over-Ear | Closed Back |


? Koss Pro4S, an over-ear headphone designed for professional studio monitoring.

Koss is a major brand with a huge history in the audio and headphone world that dates back to 1958, since then they have created an infinite number of headphones with some extremely popular models that have gained massive acceptance like the:

  • Koss ESP950 – a premium electrostatic headphone with an impedance of 100,000 ohm, being sold since 1990
  • Koss ProDJ200 – Updated version of the Koss ProDJ100
  • Koss Porta Pro – Recently also released in a Bluetooth variant as Koss Porta Pro Wireless
  • Koss Pro4/AA – An industry standard since 1970 and still in production

The Koss Pro4S features a new SLX40 element that Koss promises to be tuned for reference

The Koss Pro4S is born as a studio headphone that promises flat and accurate response, we will see during our soundtests how they perform. Much like the Sony MDR-7506, the Koss Pro4S is another highly popular model in the professional and monitoring world and they are direct competitors.

The cups and earpads of the Koss Pro4S have a special design that Koss names “D-profile” and which was first introduced in 1976 with the Koss Pro/4AAA – read more about them in the “Comfort” section.

The headband is made of aluminum, as well as the earcups, some details are built in plastic like the headband-earcups connection piece but beneath the plastics the mechanical hinge is fully constructed in metal.

You can buy the Koss Pro4S in black color.

FIND ALL: Headphones Scores Compared

MORE: Headphones Reviews

SEE ALSO: Headphones Technical Specifications

Koss Pro4S Review

Tests & Scores


Advanced Features

The Koss Pro4S offer some advanced features such as:

  • Dual entry – each earcup has an entry connection for the detachable cable. After the cord is attached to one side, the opposite one becomes an output for pass-through listening or daisy chaining.
  • Pass-Through listening – monitor through multiple headphones connected in pass-through mode.
  • Daisy chaining – connect several Koss Pro4S together in a linear series.



Koss Pro4S weight in Ounces and Koss Pro4S weight in grams.

MORE:  Headphones Weight Comparison

SEE ALSO: Earphones Size Comparison


Accessories & Packaging

The Koss Pro4S unboxing results in a a 1.4m coiled detachable cable, a 6.3 mm adapter and a lovely carrying/storage hard case. Everything comes inside a clean designed packaging.



Bass & Sub Bass

The Koss Pro4S mid-bass is punchy and fun, able to cover any track without issues.

On the other hand, the lowest end have a conservative sub-bass that could struggle with very sub-bass demanding genres.

Their sort of conservative tuning makes their bass less invasive allowing more space for mids and highs.

An EQ makes their bass a bit punchier but sub-bass can become distorted.


MORE: Earphones & Headphones Amplification Power Comparison

MORE: Best Basshead Earphones

SEE ALSO: Best Fun Sounding Earphones Chart

Koss Pro4S
Koss Pro4S
Koss Pro4S
Koss Pro4S


Mids & Vocals

The Koss Pro4S mids are warm, yet offer a clear overall sound with slight mid-bass bleed but not too congested lower vocals – with a tint of laid back style.

Higher mids are crisp and not recessed but can become a bit harsh at times.

Applying an EQ, lower vocals can be cleared up, removing their distant feel and can be emphasized efficiently without introducing boxy nor tinny sounds. Higher mids should not be EQ’ed up, as they already showed some harshness.



Highs & Treble

The overall highs of the Koss Pro4S have good brightness and enough detail. Some piercing peaks can show up with very strong peaks but sibilance is not an issue with them.

With an EQ their highs become much brighter and detailed but also frequently sibilant and piercing.


Koss Pro4S
Koss Pro4S
Koss Pro4S
Koss Pro4S


Sound Leak

The sound leaking out of the Koss Pro4S is substantially subdued and not easily hearable by nearby people when listening music at a moderate and moderate-high volume.


MORE: Best Headphones for Libraries Chart

SEE ALSO: Best Earphones for Bed

Meze 99 Classics – Review


Sound Isolation

The sound isolation provided by the Koss Pro4S is noticeable, with a strong reduction of surrounding noises. Their level of isolation is remarkably stronger than most average headphones without having to recur to high volume settings.


RELATED TO THIS: Active Noise Cancelling Headphones Reviews

Koss Pro4S
Koss Pro4S
Koss Pro4S
Koss Pro4S



Koss mentions that the Koss Pro4S feature their iconic “D-profile” earcup that ergonomically mimics the shape of the ear improving their seal and offering a natural fit for long working sessions; indeed, the comfort and fit provided by their earcups, memory foam padding and overall super light weight of the units makes them pain-free and effectively wearable for hours without issues.

Their headband padding, soft earpads with pleasant protein leather material, detachable cables and dual entry system add up to their ease of use and comfort.

Moreover, the movement range of their earcups reach 135 degrees of rotation and can be tilted by 90 degrees.

For transporting and storing they can be fully folded and/or are able to lay totally flat.


RELATED: Best Earphones for Daily Commute

MORE: Most Comfortable In-Ear Headphones

Koss Pro4S
Koss Pro4S
Koss Pro4S
Koss Pro4S


Response to Equalization

The response to EQ of the Koss Pro4S was highly efficient on frequencies ranges like lower vocals which could be tuned for clearer and more alive sound without boxy nor tinny issues and brightness and detail of their highs which could be noticeably emphasized.

Among the less performing EQ aspects, sub-bass could become distorted if bumped up too much, sibilance and piercing highs became frequent when pushing for brightness and detail.


MORE: Editor’s Picks Earphones Chart

MORE: Best Bang for the Buck Earphones


SEE ALSO: Coupons – Discounts – Deals – Promo Codes – Sales Deals


Size & Fit

Koss Pro4S size and Koss Pro4S fit.


Follow us:


Get the latest reviews on your favorite social network

Scores Scores

Koss Pro4S Scores

FIND ALL OUR: Earphones Reviews / Headphones Reviews

MORE: Best Earphones Charts

Buy it from:


SEE ALSO: Coupons – Discounts – Deals – Promo Codes – Sales Deals

Frequency Response (raw)

Koss Pro4S Frequency Response Curve

Koss Pro4S Frequency Response Curve
Koss Pro4S Frequency Response Curve

RECOMMENDED FOR YOU: Headphones Frequency Response Curves

SEE ALSO: KZ Headphones Frequency Response Curves

Koss Pro4S Technical Specifications


TypeOver-Ear Closed
Driver UnitDD
Power Capacityunknown
Impedance35 ohms
Frequency Response10-25,000Hz
Cordsingle sided coiled cord
Cord Length1.4m
PlugStereo mini plug
Supplied AccessoriesCoiled cable, 6.3mm adapter, hard carrying case

MORE: Single Dynamic Driver Headphones Reviews

MORE: Amazon Coupons & Deals

MORE:  Coupons – Discounts – Deals – Promo Codes – Sales Deals

SEE ALSO: Banggood Coupons – Discounts – Deals – Promo Codes – Sales Deals

SEE ALSO: Aliexpress Coupons – Discounts – Deals – Promo Codes – Sales Deals


Koss Pro4S FAQ

How many drivers does the Koss Pro4S have?

The Koss Pro4S is a single driver headphone. Which means that the Koss Pro4S has 1 driver per side.

What type of headphone is the Koss Pro4S?

The Koss Pro4S is an over-ear headphone.

The Koss Pro4S is an open, semi-open or closed back headphone?

The Koss Pro4S is a closed back headphone.

 Does the Koss Pro4S have a microphone?

The Koss Pro4S does not have a microphone and a remote.

What is the price of the Koss Pro4S?

You can check the most up-to-date price of the Koss Pro4S by following THIS LINK.

Where can I buy the Koss Pro4S?

You can buy the Koss Pro4S HERE

Which Koss Pro4S colors are available?

The colors available for the Koss Pro4S are: black.

What cable do the Koss Pro4S have?

The Koss Pro4S have a detachable,  single-sided, coiled cable.

What cable connection does the Koss Pro4S have?

The Koss Pro4S cable connection has 3.5mm mini stereo plug.

Are there replacement cables for the Koss Pro4S ?

The Koss Pro4S cables can be replaced with 3.5mm replacement cables.

Are there upgrade cables for the Koss Pro4S ?

The Koss Pro4S uses 3.5mm which are very popular standard cables. You can buy any cable with a 3.5mm connector to upgrade the cable.

Does the Koss Pro4S have Bluetooth / The Koss Pro4S is a wireless headphone?

The Koss Pro4S is not a Bluetooth wireless headphone.

Is the Koss Pro4S compatible with Apple devices?

The Koss Pro4S is fully compatible with Apple devices.

Is the Koss Pro4S compatible with Android devices?

The Koss Pro4S is fully compatible with Android devices.


Koss Pro4S Photos

We highly discourage anyone from trying to apply our testings to your own earphones, the risk of damaging or permanently breaking your iems is absolutely probable to happen. With our standardized equalization and amplification tests we push the limits of the earphones to the extreme. If anyway you decide to do so, we cannot be held responsible of the damage done to your equipment. Do it at your own risk.

Koss Pro4S