The Pro4S over-ears ($149 in the US; available in the UK and Australia for about £130 and AU$190) are part of a new trio of headphones recently announced by Koss, but while the SP330 and SP530 take aim at the average music-loving consumer, the Pro4S are studio monitor headphones designed to be used in a recording studio by audio engineers, producers, and anyone else at the source concerned with a clean sound without aural additives.
Koss is up against tough competition in this marketplace since many of the current best-selling "professional" headphone monitors like the Sennheiser HD280 and the Sony MDR-7506 have remained in the winner's circle for more than a decade, but the Pro4S hopes to deliver the audiophile's fantasy of an accurate, noise-attenuating headphone that can be used for both studio monitoring and everyday listening.
Headphones built for studio professionals are concerned a lot more with sound design and all-day comfort rather than modern notions of aesthetic appeal like bright colors and flashy materials, which could explain why some of the industry standards have remain aesthetically unchanged (and kind of ugly) since the 1990s.
The Pro4S, on the other hand, puts a modern spin on some of those classic headphones without sacrificing necessary comforts like a ear cups wrapped in memory foam, a wide, generously padded headband, and a supremely lightweight chassis that weighs just under seven ounces.
I tested these headphones for a week and they're exceedingly more comfortable than the bulky Sennheiser HD280s, to the point where they become almost unnoticeable while they're on.
Instead of the usual circular padding we see on most over-ear headphones, the Pro4S features D-shaped aluminum ear pads that are offset at an obtuse angle relative to the headband so they sit a little further back on your head, which actually feels more secure and resistant to accidental movement while you're listening.
Music professionals will be thankful to see that the Pro 4S gives the option to connect the included coiled cable to either the left or right side. Additionally, the empty jack can still output audio so anyone else with their own headphones can also plug into the listening party without bringing around one of those annoying little headphone splitters.
The ear cups swivel 180 degrees to allow the listener to monitor with an open ear, and both ear piece sections fold up flat against the headband for compact travel in the ballistic nylon carrying case included with the headphones.
You'll also find a smaller pouch with a quarter-inch adapter inside so you can plug the headphones into a home receiver or mixing board, but I was disappointed to see that Koss doesn't include another cable with an in-line microphone and music player to navigate tracks and adjust volume on the fly.
Like all of the headphones Koss sells, the Pro4S are backed by the company's widely celebrated lifetime warranty. If they ever fail for any reason (even if it's your fault), all you have to do is send them to the company's headquarters in Milwaukee, Wis., along with a check or money order for $9 and you'll get a brand-new set in a week or so -- no questions asked, nor proof of purchase required.
I've done this myself on two occasions with my PortaPros , and even though both instances were my fault, Koss was great about getting me a new pair in about a week. A true-to-its-word lifetime warranty goes a long way for someone like me who isn't afraid to test the durability of their headphones, and Koss gets major value points for being one of the only companies to make it so easy to get a replacement.
It's worth restating that the standard protocol for judging headphones doesn't apply to studio monitors. Of course, all sound quality is relative to your ear and the music you're playing, but the difference is that the Pro4S makes no compromises for modern listening preferences that lean heavily toward compressed music.
As such, the extremely flat register also means that electronic music generated from a computer sounds lifeless and dull compared to what you'll hear from extremely dynamic V-Moda M-100 headphones when playing the same track, but you should press play expecting this organic response from the Pro4S.
Rated at 35 ohms, these also aren't the most powerful studio monitors that you can buy compared to the Sennheiser HD600 , but they're also a lot less expensive and don't require an external amplifier, which is convenient for folks who just want to plug the headphones directly into a phone and start jamming.
The fact that these are closed-back headphones means that their passive noise-attenuation will likely be sought out for studio-tracking purposes where the engineer can ensure sound won't leak out of the headphones and make their way onto the recording.
The snug fit of the headband holding the ear cups in place also works well to keep ambient sounds away from your ears when you're playing music, making them a solid contender for use on a commute or elsewhere outside a recording studio.
The Grado SR80i is another option in the same sub-$150 price range that updates Grado's classic open-back design with smartphone controls, but the premium tier also offers plenty of options that can reach into the $500 and up range. If impedance and power are at the top of your list, the Beyerdynamic DT880 is worth a glance.
The Koss Pro4S are a well-built pair of studio monitor headphones with the audio chops to compete with big name competitors that have proven their value over the course of the last twenty years. They're not quite as fun to listen to as the Audio-Technica ATH-M50 in terms of versatility, but you get modern features like memory foam cushions, dual-entry jacks and of course Koss's unmatched lifetime warranty.
The Pro4S are a sound purchase if you understand and accept that these are basically the antithesis to the "big" sound that companies like Monster have built an entire industry upon. Brands such as Monster make headphones that are great for cranking up the volume and blasting tunes, but the Pro4S are meant for a more attentive user who really wants to pick out the nuances of the recording. If you fit into that profile and have $150 to spend, you won't be disappointed by the Pro4S.