Koss Pro4S Headphone Review

Build Quality
PRICE $150

Big on comfort
Lifetime warranty
Timbrally rich
Lacks mic and phone controls

The Koss Pro4s doesn’t sound like your daddy’s Koss, not by a long shot. It’s the best new Koss in ages.

Koss was founded in 1958, so it’s as old-school American hi-fi as you can get, and I’d bet lots of older audiophiles have fond memories of their Pro4AA headphones from back in the day. Koss still makes that headphone, and sound-wise, it’s about as subtle as a 1970 Chevelle SS 396 muscle car. As for this new Pro4S, it’s closer to a new Camaro—the sound is far more refined. The sharply sculpted, cast-aluminum ear cups are the first clues; the handsome design has a contemporary look and feel. The sound balance was just a tad warm, but the Pro4S wasn’t lacking in resolution as I played familiar tunes. The sound was right on the money. Not only did my audiophile tracks from Reference Recordings, MA Recordings, and Chesky sound open and clear, the harshest, most overcompressed downloads didn’t tear my ears off. The Pro4S lets the music speak for itself.

The sound of each Koss headphone model is tuned by ear by President and CEO Michael J. Koss, along with members of his family, friends, and the company’s engineers. Their working method is right on target. The Porta Pro on-ear headphone that was introduced in 1984 is one of Koss’ most iconic designs, and it’s still hugely popular. Long before the Porta Pro debuted, the Pro4AA headphones set the standard for full-size Koss headphones. Few other headphones endure the way Koss designs do.


Back to the Pro4S, it features Koss’s “D-profile” ear pads, first seen on Koss headphones in the 1970s. The “D” shape conforms to the contours of the ear better than more common round or oval cushions. The Pro4S is a closed-back design, and it does a decent job blocking external noise, while still managing to sound pretty open and spacious. The user-replaceable 4.5-foot coiled headphone cable fits with the “pro” heritage. The hinged headband allows the Pro4S to fold into a small bundle. The metal headband is cushioned by soft foam wrapped in breathable mesh, so comfort levels are decent. You also get a sturdy carry case.

Next, I started comparing the Pro4S with my go-to recommendation for full-size headphones in this price class, the Audio-Technica ATH M50x. First thing, the M50x has fuller but flabbier bass than the Pro4S’ generous low end. Antonio Sanchez’s hard-hitting drum solos from the Birdman soundtrack album sounded a little canned and closed-in over the M50x, and far more open over the Pro4S. Vocals were more naturally balanced over the Pro4S. Later, I popped on a pair of Sennheiser Urbanite on-ear headphones, which sounded darker and less transparent than the Pro4S. The Urbanite lacks the Pro4S’ refinement.


The Pro4S is easy to drive, so I spent hours listening with my iPod classic, but this headphone benefited from partnering with amps like my Schiit Audio Asgard 2 ($249). That combo generated more and better-defined low end; the Pro4S’ prodigious bass output caught me by surprise. There was lots of it, without shortchanging definition.

Koss’ Limited Lifetime warranty policy (for the original owner) started 30 years ago, so anyone who bought, say, a Pro4AA or Porta Pro back then may have worn a few sets of headphones, but can still have their broken headphone repaired or replaced by Koss. That level of customer service is rare for any consumer product, but rarer still for truly affordable products like Koss headphones. To make a warranty claim, all you have to do is ship the headphone back to Koss with a check for $9 to cover return shipping. If the model is no longer made, Koss will replace the headphone with an equivalent model. That’s extraordinary.

The Koss Pro4S departs from the company’s signature sound; it’s more transparent and open but still very much in the tradition. I like that.

Type: Over-the-ear
Driver Size: 40mm
Impedance: 35 ohms

Company Info
(800) 872-5677

staceyholmes's picture

Great move, Koss Pro4s! There are a lot of different headphones, but this one is just awesome. And thanks for your review. You know so much about Koss Pro4s... so much so that you made me want to learn more about it to write an article for hire essay writer online website. I think everyone should know about the best headphone.