Hi Stan,

Thanks for that. I believe those are the ones that Dave Cawley of Sound Hi-fi uses at shows (together with the ANT Amber 3T headphone amp). I've heard them, and they are very good, but I'm somewhat reluctant to spend £500-600 on headphones

What I'm hearing at the moment from the PRO-4 AAs is, sonically, a pair of £200-250 headphones with a £69-00 price tag (finished to an impressively high standard for their bargain basement cost), which is really quite remarkable..... They're certainly in my opinion sonically superior to the Sennheiser and Beyer Dynamic price eqivalents I've heard (and I mean the £200-250 ones!) I also love their 70s retro looks!

Weight-wise, they're heavier than is the norm with headphones these days, but being quite a big bloke, I didn't find it a problem. I suspect that most people wouldn't either, unless they were girly-men who couldn't cope with using anything but featherweight headphones (). I feel therefore that their apparent 'excessive weight' is somewhat overplayed, as is the 'sweat factor'. The latter, however, may be an issue in the summer months.

The PRO-4 AAs also shut out external noise extremely effectively (probably the most effectively with any headphones I've used to date), which certainly aids detail retrieval, as one's ears are immersed in total inky-black silence, from which music then emerges rather spookily. Crucially, they are also as effective at keeping noise out the other way, so that only the user is aware of any music being played, making these headphones ideal for use late at night where the slightest noise may disturb others sleeping.

In terms of absolute sound quality, they don't quite have the overall finesse, airy spaciousness, and that 'out of the box' sensation of the K701s or top-notch open-backed headphones, and certainly the Denons you're referring to. However, the level of detail retrieval and insight into the musical programme listened to, no matter the genre of music is, quite frankly astonishing at this, or indeed any price. If you enjoy forensically examining the minutiae of information in recordings, then these are the cans for you!

There is also a real sense of cohesion, with voices and instruments taking their correct place inside the acoustic space, creating a sense of realism, and giving their overall presentation an addictive musicality that encourages lengthy listening sessions. In terms of tonality, there is plenty of extension and sparkle at the top end, superb midrange clarity, and tight but 'articulate' bass. One can certainly hear why these were/are used for monitoring purposes in broadcasting studios.

Koss, IMO, have used their huge experience and no doubt unique access to specialist in-house materials, employed successfully for well over 30 years in the same design, to keep costs down, and carefully updated key components, whilst very cleverly voicing the PRO-4 AAs sympathetically to the originals, but at the same time also adding a more modern and incisive sound.

It's an incredible achievement for £69-00, and ably demonstrates that with some of the 'fancier' looking headphones on the market, most of what you're paying for is aesthetic frippery... Now where have I discovered that before?

For me, even at this stage when they're not run in yet, and when I haven't yet got a full handle on their sonic signature, at £69.00, they represent an unmitigated bargain, and thus easily represent a superb example of the SPPV we value on AoS. I can't see these being anything other than an enhancement by Koss of the original design (the same Koss who first produced the PRO-4 AA) - thank goodness!

Right, I'm off for another listen - laters

Marco.