My issue with the current Pro 4AA headphones is that they are head crushers and very uncomfortable to wear.BoblK wrote: ↑18 Jan 2019 02:19Tinkaroo wrote: ↑17 Dec 2018 16:11The impedance on the Koss Pro 4AAA from the mid 1970s is listed at 250 ohms and the same would apply to the Pro 4AA. That 250 ohms seems pretty standard for many headphones by a lot of manufacturers.
An interesting article on headphones impedance:
https://www.cnet.com/news/headphone-buy ... ce-models/
I had a set of the Pro4AA's back in the early 70's up through about '82. Your right, the impedance was 250 ohms. The original 4AA's sounded great. I have not heard the current 4AA's. From what I have read they don't sound as good as the originals.
The older circa mid 1970s 4AAA sound better and were more comfortable, but the original earpads tend to have turned to rock, and Koss no longer supplies pads for them. You need to remove the old rock hard pads and add a more comfortable replacement. Other than that the rest of the headphones have stood up very well.