Summary: I was very excited to use these in conjunction with my Old Sansui receiver and Yamaha CD player, and the first time I plugged in, I was shocked. Not by how good it sounded, though, rather how different it sounded. I've always had to tinker with EQ levels with other headphones (usually around Bass - 10 Treble - 8) and I immediately noticed alack of bass compared to what I was used to.
Pros: EXTREMELY Balanced
Cons: Weight, but doesn't really matter to me with this sound quality
Summary: I have used PRO4AA for about 15 years. The warranty has replaced the phones several times because the joints that hold the band together comes apart and have so many gluings before I send in for repair. Also the insulation on the cord after several years will crack to the point of needing replacing. As a licensed broadcast engineer, now retired, I need critical headphones that seal out the sound so that I can hear audio.
Summary: I am, admittedly, a KOSS collector - I have an example of every single (full-sized) model of Dynamic and Electrostatic KOSS have ever made! The 4AA is the exception - I have exactly 100 mint, boxed examples from 1974 to 2007 -Anniversary Specials - you name it. Ok, I'm a KOSS nut. I use 5 pairs in my professional studio and these all date from September 1977 - not a single fault in over a half-million hours of monitoring rock music and jazz! So good they're Spooky.
Summary: Glad to see the return of the metal frame around the earpieces. These phones are best for analog listening, though digital sound's amazing as well. You won't find a better headphone for the price, like to see the Pro 4 AAA’s remade as well. For the revival of the vinyl LP, these phones are the best companion to vinyl listening.
Pros: Solid bass,gorgeous midrange
Cons: Earpad foam could be better quaility,known to deteriorate
Summary: I purchased my Pro4-AA headphones in 1977 while I was in college in TX after auditioning many other sets at numerous high-end stereo stores. Honestly, I could have spent a lot more money but nothing sounded better than these for under $200 (1977 dollars). During the short time that Koss discontinued the Pro4-AA I had at least two professional Sound Engineers try to buy my set for a lot more than I originally spent for them. Guess what...
Pros: Great presence, low bass through high treble. Fantastic isolation!
Summary: I bought mine in High School in 1969. They've been with me ever since. Navy usage in barracks, x-country trips, survived 2 kids. went thru 3 pair of pads. They are finally wearing out no treble on Leftside, and the headband is shot so another pair will be gotten for me for Father's day.
Summary: SUPERIOR CONSTRUCTION, DURABLE AND BUILT TO LAST (not for the weak of heart weekend warrior) I HAVE PERSONALLY TRIED SEVERAL DIFFERENT SETS OF HEADPHONES, and BELIEVE ME - YOU, THESE "KOSS PRO4AA HEADPHONES" BEAT THE BAND, HANDS DOWN. P.S. - I'VE BEEN USING "KOSS" AUDIO PRODUCTS EVER SINCE I FOUND THEM, THE "NEWER PRODUCTS" PALE BY COMPARISON TO THE FAR SUPERIOR "KOSS" PRODUCT LINE.