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Koss Pro4AA: The Ultimate Closed-Back Headphone

Koss Pro4AA headphones set the standard for full size professional headphones. They were introduced in 1970 as the first dynamic headphones to deliver true full frequency and high fidelity performance with impressive noise isolating capabilities.

Key Features

    • Connectivity Technology: Wired
    • Frequency Response – 10-20,000 Hz and Impedance – 16 ohms
    • Closed-back circumaural design with titanium-coateddrivers
    • Koss’s proprietary Dual Element design with bass port
    • Plush leatherette and memory foam ear pads
    • Oxygen-free copper voice coils for distortion-free sound
    • Frequency response range of 15Hz–25kHz

Sound Quality

The Pro4AA delivers warm, smooth bass, lush mids, and sparkling highs in a beautifully balanced package. From thundering hip-hop tracks to intimate jazz combos, it brings out the best in your music.

The soundstage is spacious for a closed-back headphone, giving instruments room to breathe. Imaging is precise enough to pinpoint individual vocalists and guitarists.

Whether you seek to analyze recordings or simply enjoy them, the highly resolving Pro4AA brings out micro-details missed by lesser headphones.


From the stainless steel headband to the buttery leatherette ear pads, the Pro4AA oozes luxury. The build quality promises years of rigorous use.

The memory foam ear cushions are comfortable enough for all-day listening sessions. The ear cups fold flat for traveling and storage.

Customer review

I bought my first pair ~1971, when I had just an AR Amplifier and AR Turntable. I had to make an external switch and headphone adapter for the old amp. Somewhere along the road I was introduced to Sony MDR V6’s (~’89) – and one of our cat’s chewed the plug off the old Koss set – and the plug off my Stax electrostatic headphones, too. The Sony’s were available – the 4AA’s weren’t. The 4AAA and 4AAT were tried – but returned. My 4AA’s and Stax phones found the bottom of a junk box – a spare set of Sony MDR V6’s were bought – followed by all too frequent new pads. Over four years ago, I checked Koss’ site – they were back making the 4AA’s! I found them on Amazon – and ordered a set (6/11). The box they are in looked like the original – flimsy! I didn’t care before – or then – the phones looked identical to the old ones – and they are still made in the USA! The fluid filled ear pads were soft and pliable. They fit as I remembered – properly on my big (7 7/8 hat size – with short hair.). Great room isolation. Excellent midrange and highs combined with un real, but properly slightly subdued deep bass extension. The Sony’s have a subdued midrange, bright highs, and boomy mid-bass, in comparison. It could be my 67 year old ears – they do have a 3 – 5 kHz dip in response. I like the flat response and distinct/controlled bass of the Pro-4AA’s. I like jazz and ‘classic’ rock & roll, and older r & B, too.

One use the Pro-4AA’s excelled at – and still do – is listening to short wave broadcasts, as well as DXing, the process of listening to distant and weak stations. They were great – and the new ones are as well. These days I find myself listening to strong old standby stations, like Radio Australia, in the early AM hours and the Pro-4AA’s keep me from bothering my wife – or the cats! I moved nearly two years ago – and, recently found a box of goodies I hadn’t gone through yet. At the bottom were my original Pro-4AA’s! I may contact Koss and see what they would do to refurbish them – they have nostalgic value as well as use value – they are that good. Of course, meter my words by my likes and age… I like a flat response and prefer deeper, but not boomy, bass… and I am ‘older’, or so I am told! Oh, and my big head doesn’t mind the ‘phones weight or pressure. And… some folks don’t like what I do… imagine that!

Edited 10/6/15: After posting my review, I searched for and found my original Pro-4AA’s remains, still less the plug but now with a deteriorated strain relief on the coiled cord’s headphone end. Comparing them to the newer units resulted in the only visible difference being the relative height of the protrusions, which were surrounded by ‘Left’ and ‘Right’ being shorter. The headband, ear cushions, cable, etc, looked identical, except for the wear. I contacted Koss – and their return shipping charge had increased from $5 to $9 in over two decades. I put the remnants in a box with a letter describing their history and shipped them via Priority Mail. They didn’t patch them – they sent me a brand new pair! They arrived in new shape – perfect, although initially quite tight. That was remedied by leaving them open over night on my Tivoli Audio Model One AM/FM table radio (My wife had suggested a watermelon…). Now they are indistinguishable from my Amazon ordered ‘phones. American made – and a real lifetime warranty!!

Customer questions & answers

Q: Which ones are better the 4aa pro or the qz99?

A: No idea. Never touched a qz99.I love the sound quality of the PRO4AA, a bit heavy. May not be the best choice if you are going to wear them for a couple of hours. 

Q: what is the length of the cord on the koss pro4aa?

A: I’m sorry for not answering sooner!!!! I’m a music lover of the 70’s, these are what I used & prefer. So first protect your invest, all studio style that have to be connected to your sound device. You will have a length from the 1/4″ plug to the connection on the headset, in it coiled shape, around 5 feet. Do yourself a favor, buy the extension cord as well, why? What will cause more damage to your head set sound, is the stress that is put on the cord & to the connections. You’ll hear sound scratching, R or L even both side or sound cut out due to a short. My advice is plan where you will be enjoying your sound & how much cord space you’ll need without stressing it out.

Q: Does anyone know what headphone case fits these? I love them and want to protect them.

A: Don’t know if this helps. Id say the size of a bowling ball, with other attachments (extended headphone cord). I don’t have mine in a case, I like to show mine and use a styrofoam head bust. Otherwise, there isn’t any.

Q: Can anyone identify a hard shell case that will fit these cans? Thanks very much! CD

A: I made my own.

Q: Could someone please tell me all that comes with these headphones? Any sort of case? Thank you!

A: No case. Don’ let that stop you. These headphones are superior to many that come with a case.

Q: Does anyone know what headphone case fits these? I love them and want to protect them.

A: Don’t know if this helps. Id say the size of a bowling ball, with other attachments (extended headphone cord). I don’t have mine in a case, I like to show mine and use a styrofoam head bust. Otherwise, there isn’t any.
With lush sonic beauty matched by premium aesthetics and comfort, the Koss Pro4AA stands tall among the world’s finest headphones. For the ultimate closed-back listening experience, look no further.


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