Koss Pro4S Studio Headphones Review

Photo taken by the author.

Just as the AKG K371 totally crushed the Audio-Technica M50X, the Koss Pro4S destroys the classic Sony MDR-7506. These are more than worthy of the Koss legacy, and honestly I think they’re the only studio pair that the company should be selling right now.

Yes, that’s a dig at the Koss Pro 4AA, one of the oldest studio headphones still in active production. I was curious as to why Koss is still selling that ancient pair, so I bought and reviewed one…and I didn’t like it much at all. It was the first Koss product that didn’t immediately charm me, and indeed the first Koss product I thought was a miserable waste of time. On social media multiple representatives from Koss suggested I should check out the Pro4S instead, and they offered to send me a review unit.

Rather than take them up on it, I decided to buy this closed back pair myself, especially after seeing that in spite of carrying a standard retail price of $149 (official product site), the Pro 4S can often be had for the studio headphone “sweet spot” of $99, which is what I paid on Amazon. None of the links in this piece are affiliate links, and if you’d like to check out my reviews policy it lives right here.

Photo taken by the author.

The Pro4S impressed me from the moment I opened the package and found a hard case inside. It’s rare to see a hard case included standard with headphones at any price, and even then it’s usually reserved for the $300+ crowd. The case has a rugged textured material on the outside and an emblem proudly displaying the Koss logo, and it’s more than sturdy enough to protect the headphones from damage. Inside, you get the headphones, some documentation, and a small Velcro-backed pouch which contains a short 4 foot coiled cable and a 6.3mm adapter.

Moving past the excellent case… the sound quality, comfort, and build all live up to that exemplary first impression. The sound is truly brilliant, and is a slightly cooler-sounding companion to the amazing AKG K371 and K361. It doesn’t quite have the same level of bass energy as those excellent pairs, and the upper midrange and highs are both just a touch more strident…but the Pro4S is still an awesome-sounding neutral headphone that presents sound to you just as it was mixed.

The bass is incredibly accurate and balanced, with a satisfying punch and quality that feels almost speaker-like, and is never boosted over what’s present in the material. The lower mids are a little bit recessed and withdrawn, which is what gives these a crisper, brighter tone than some other studio pairs. On the plus side, this does help separate the bass response from the rest of the sound. The colder midrange means that female vocals sound a hint thinner and sharper than “true neutral,” but it’s not so overdone that you won’t adjust to it in the first day of listening.

Photo taken by the author.

If you’ve heard the Sony MDR-7506 or any of Beyerdynamic’s DT models and found them too harsh in the treble, but still enjoyed their overall character, then the Pro4S will be your new favorite headphone. It renders detail with incredible authority and it’s equally perfect for enjoying a good album, movie, or game, or checking for flaws in a recording during a professional mixing session. It’s in the same excellent ballpark of quality as the AKG K361/371 models I’ll never stop gushing about, but with a cooler, slightly more bright sound that’ll appeal to those who want detail first and bass response second. You will truly have the “I’m hearing things I’ve never heard before” audiophile experience.

Even better, in the comfort and build departments, it actually beats those already-iconic AKG pairs. Koss obviously learned clear lessons from all of the studio greats, and then went for some small refinements rather than trying to invent a wholly new frame design. They’re tremendously light to the point of feeling like nothing at all in spite of a sturdy aluminum and plastic build. The headband is amply padded, and the D-shaped memory foam ear pads are at the complete other end of the comfort spectrum from the abysmal Pro 4AA. In spite of their small profile, I still have two extra clicks of adjustment on my larger head, and the flexible swivel and dense padding easily seal around my head and glasses for a surprising amount of passive isolation.

This is a headphone you’ll instantly feel comfy in and that you can wear all day. It’s perfect for long sessions of production work or fun. And the solid build means they’ll probably hold up for years, especially if you store them in the case. Unlike the weirdly consumer-styled AKG models, the Pro4S is clearly inspired by other famous durable studio pairs. The ear cups are made entirely of aluminum, and the adjustment mechanisms and headband core are also made out of the lightweight metal. The joints and swivels are sturdy without any hint of creaking or weakness after a week of heavy use, and I imagine they’ll stay that way for a long time. If they don’t Koss’s excellent lifetime warranty is always there to save the day.

In spite of their small profile and light build, the Pro4S packs in tons of comfort. Photo taken by the author.

Another smart design decision is the dual entry cable system. The headphones have a standard 3.5mm port on each ear cup, meaning you can choose which side the cable attaches to. The port is a tiny bit recessed, but not so proprietary that you couldn’t potentially use a third party cable as long as its plug is relatively thin. The included coiled cable is labeled on the box as being six feet long, but that’s when it’s stretched out. In practice, it’s only about 4 feet or so. I had to move my amp on my desk in order to plug it in, and although it’s a nice and pliable cable I wish it was a foot longer at least.

The short cable is literally the only thing I can reasonably complain about here. For the price, these offer an unreal amount of sound performance that rivals the best of the competition. The build feels like it’s almost too light at first, but quickly shows many comfort advantages, and the heavy use of aluminum makes these far sturdier than their weight implies. And the included hard case gives these an additional edge on every other popular studio headphone.

In spite of the K371 and K361 having some of the most technically impressive sound performance levels for their respective price points…the slightly crisper sound of the Koss Pro4S is more in line with my personal tastes when I’m not trying to review headphones. The Koss Pro4S is my new favorite studio headphone, and I love that it’s built like a rugged professional pair compared to its current AKG counterparts. All three of these swap around constantly as far as which has the best price, and you can’t go wrong with any of them, so if you just buy the cheaper one that’s fine.

The Koss Pro4S is my new default recommendation to anyone looking for this sort of headphone, unless you think a tiny bit of brightness up top isn’t your thing. Comparing it against the K361 and K371, I’m reminded of one of my favorite moments from Top Gear:

The AKG models are the only two headphones worthy of comparison to the Pro4S in my opinion, as all three of these easily sit atop the massive studio headphone pile I’ve reviewed over the last six years, and those I’ve used in the last 15 years working in the audio production field.

These have a smooth profile and sit nicely on my head. Photo taken by the author.

The 7506, M50X, 280 Pro, and many others just aren’t quite as good. If I’d heard the Pro4S back in 2014 when it first launched, I may never have gone on such a headphone review odyssey and indeed might have just carried on reviewing music and games instead of headphones. They’re that excellent, and clearly benefit from Koss’s years of audio engineering experience.

Koss should absolutely stop selling the nostalgia-fueled Pro 4AA, and just pump all their marketing time and effort into the Pro4S. Heck, maybe they could try making a beige color for those long time Koss fans out there. It’s a fantastic headphone that won’t disappoint. They have a gaming headset cousin of sorts available in the Koss GMR, but that is a tale for another time!

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