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Old 'phones: Koss Pro-4a. Anyone have any info?

post #1 of 14
Thread Starter 
My dad had some old headphones in the basement that he's not using anymore. I believe the model number is Koss Pro-4a, but the writing is rubbing off and I can't be sure. Other tan that they are in excellent condition. They are closed headphones, with a cord attached to one ear and olive-green colored earpieces. They have a black headband with foam underneath. Does anyone have any info on these?
post #2 of 14
I remember finding a pair of these collecting dust in a music instrument store some time ago. I also was very interested, but disappointed at the end. First of all they're big, extremely heavy and clamping on my head. I couldn't wear tham for more than 15 min. The sound was nothing exceptional either. Collapsed soundstage and slow boomy bass. In a word, IMO you can do a lot better for not a lot of cash today.
post #3 of 14
These are the Koss Pro4AAs. They are still in production. They're decent. I'd mainly use them for studio monitoring but they are really uncomfortable and there are much better phones out there. They're certainly better than the craptacular headphones given with portables and stuff but I'm still conflicted as to whether or not I should even have them as back up 'phones. Biggest problem is comfort, but your head may be different, therfore YMMV.
post #4 of 14
I used to use them (and the 'AAA follow-up) on the flight line hooked up to a walkman. The fluid filled ear pieces work great, but they fossilize quickly. They certainly do clamp ones head effectively - which is useful if you are moving about.

Two pair died due to cable problems between the earpieces. The poor 'AAA died after a certain woman sat on them. If you saw her, you would feel sorry for anything that had to support her. No, she's NOT my wife!!!!

Either way, I don't miss those headphones.
post #5 of 14

A few years ago I sent my ancient Pro4AA back to Koss for a factory rebuild. If I recall, I only had to pay shipping. They are still not so comfortable. As soon as I put them on, I had flash backs of Zeppelin and Jimi. Just this week, I started burning them in to see if they sound improves. 

post #6 of 14

My Pro4AAT (very similar model) craves a beefy amplifier to drive it. I actually quite like the sound when amped properly, it's a strong contender at that price point, in my opinion. 

post #7 of 14

They are good phones for the money but do need strong amping to sound their best for sure. They need but loads of power to be driven properly.


I know when mine (when I had them) were underpowered that they sounded muffled, thin, and the bass was weak. Get a PHENIX G3 to amp them. It's a $100 OTL tube amp that should give them a dose a the power they need.


EDIT: WOW two years later and now I own a PRO4AAAT. It sounds good to me (purely nostalgia) but these do require good amping to not sound muffled and slow. Also when amped they get a tad brighter and the bass tightens up quite a bit. Are they worth full $150 when new? No for $150 they aren't worth it but I got mine from Koss directly for $60 and for $60 the are great to me.

Edited by Zombie_X - 10/1/11 at 12:09pm
post #8 of 14

I AM Older Than Dirt

Having said that, these are really nice cans. I had a pair  some time ago, in fact they were the first set I ever bought. At the time they were considered top drawer. Clean them up and use them. Frequency response is pretty good and I don't think you'd be able to replace them for less than $100.


post #9 of 14
My dad also has a set of these. He got them when he graduated high school(1975). They sound good when driven by his vintage receiver. The fluid has all evaporated/dried from the earpads and they aren't comfortable anymore. But Koss only charges $10 or so to fix them up and I've been meaning to do that.
Overall, especially if they're free, they're worth getting fixed up and keeping/using.

Sent from my DROID3 using Tapatalk
post #10 of 14

I'm new here and first time posting, but I also just got a set of Koss Pro 4A headphones almost new in box but the ear pads are very empty of what ever fluid they were filled with. I found a site that asked that I register the set for warranty use but I purchased them on Ebay and didn't want to suggest they were purchased second hand. Have any of you ever sent a set back to Koss for the warranty upgrades, and do you know if this is only some vintage models or does it include Radioshack Koss headphones? I'd like to register the Pro 4A set that I've got but don't know what year they were made and don't know what stores sold them in the day, and that's two questions they ask when registering a Koss product? The instruction brocure in my box only says that the cost of these were $50.00 and doesn't suggest the manufacture date.

post #11 of 14
I just picked up a set of these for $9 at a Goodwill store. I couldnt resist the price. It will be interesting to see how they sound with a Mont Blanc and I am going to try to find new earpads if theyre worth it...
post #12 of 14

I'm not thinking you'll be able to find/get new earpads for this model PRO-4A. If they're sent back to KOSS for warranty, they'll either ship them back with nothing done since these were produced before the "lifetime warranty" was started. Even if they did acknowledge the service, they'd send a newer set back which I've read others rage about KOSS doing that and not sending their headphones or original box back. These earpads were liquid filled and I've not read anything about being able to replentish the lost/evaporated fluid. I did read where a guy said he made a small slice along the outer edge of the pad and incerted a bid of gel pad to filll the void  enough to seal against your ears. Mine are imaculate but don't sound as full as my KOSS K/6ALC headphones which are a decade newer at least. I've got 2 sets of this K/6ALC from Koss with 1 setthat was sold thru Radio Shack.

post #13 of 14

Koss Pro 4...yeah...some of the best headphone ever made at any price.




Bullet proof, I have 2 sets, one set is 35 years old and sounds like it did when it came out of the box.

There are 2 provisos that you have to bear in mind if you plan to buy and/or use a pair:

#1- You got to man up to wear them for longer than 30 minutes...they are heavy, but that works in your favor if you want to hear the music and not you neighbors or fire trucks or atomic explosions..

#2- Not may amps are up to the specs that these phone take to do what they do best...a piss poor amp with piss poor power and a piss poor acoustic range will create piss poor performance no matter what you use...the Koss Pros 4 drivers eat power...you will crack your skull before you blow the phones.


These are studio quality and they take studio power...you know...like we had back during the Old School days....your 2014 Sony probably won't cut it.

The people who are complaining about thumping bass and lost high range are probably ( I am 100% sure) using equipment that sounds fine with lesser phones...too bad for them that they are missing the reason why there are 7 octaves on a piano.


3 thing that will always be true (if you want fidelity)

#1- Tubes beat solid state.

#2- Vinyl beats CD (aka: all Digital).

#3- The era when a true quality system that costs less than $5000.00 for the basic gear is over...you gotta spend it to hear it.

Edited by Hammerogod - 4/25/15 at 12:36am
post #14 of 14

I remember these.  I considered these nearly 40 years ago.  In the end I bought a pair of AKG K145s and my best mate ended up with the Koss Pro4s.  Comparing the 2 was like chalk and cheese.  The AKGs were light and easy to wear, the Koss were really heavy with a vice like grip on your skull.  Both were great headphones for their day.  Totally different to listen.  No matter what was used to drive the Koss they were slow compared to the AKGs electret driver, particularly in the top end percussive areas..  The Koss on the other hand had a more controlled bass.  The Koss, in my opinion, suffered the usual problem with closed headphones, a lack of soundstage but surprisingly I didn't think they were muffled.

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