So, slightly different tuning aside, the 650 is "technically" the better of the two? I'm not too concerned with tuning, because from what I understand they don't seem to be all that different, and I can always adjust them a bit with EQ if need be.

Hmm...well, $90 isn't a huge difference, and I do greatly prefer the look of the HD650s. They seem to be at least slightly better technically by most accounts as well, so I think I might go for the 650s.

My first one was bought new 3-4 years ago and my current one was bought used and of unknown provenance, but both sounded pretty much the same to me.  They both came in silver boxes and neither sounded 'veiled' to me.  They're just not artificially hot like most other headphones are.

Since I don't think I've ever actually heard a 'veiled' pair, I'm tempted to say that's where this whole 'veil' business came from in the first place.  People just didn't like that they weren't as bright as Beyers, Grados, or ATs.  Assuming there was a 'veil' which is now fixed, this is probably part of the reason why that meme still sticks around.

I have an older pair with the black drivers. There was a slight veil until Solderdude was nice enough to send me a SeNNator amp/filter. Veil is gone and FR is smooth. Sub-bass is tight, when it is on the recording. Bass is excellent. Treble is nicely extended but not fatiguing. But you can not turn it up to very loud levels. The sub-bass will start to make your head rattle and the headphones FR goes off kilter.  The sound is revealing so you don't have to turn it up to enjoy low level detail.

I have a very early HD650 (black driver, original pads) which sounds 'veiled' to some and 'dark' to others.
All stock... so including foam in front of the driver and the foam in the back.
Yes... used them without foam (and stocking as protector) and with the the little foamies on the rear removed.
While clarity improved the SQ didn't (for me) and reverted back to stock and used other means of 'improving' my HD650.

Also bought some spanking new pads.
These are 'firmer' and seem to be made from different type of cloth as well (feels and looks different, find the older pads more comfy so older ones stayed on.

Also had a spanking new (white/silver) HD600 with mint pads.

My findings (all measured on the exact same rig on the same day)

Old HD650 with old (original) pads and the exact same driver with new pads.



It clearly shows (at least to me) the difference in FR.
Funnily enough while the original pads are 'darker' and perhaps 'veiled' to me with the newer pads they sound (and measure) a lot 'fresher' and without a 'veil'.
Same driver ... just different pads.

So is the pad material the culprit, after all they do feel and look different..
Old pads and new pads but compressed (with extra force) to the exact same thickness as the old pads are compressed (by the clamp force of the HD650 itself)



Yep ... sound the same and measure the same.  New pads clamping force is untolerable, old pads ... very comfy.

So how does the old HD650 with old pads compare to a HD600 with original (new) pads.



Yep, sounds about correct, the HD600 is considerable brighter and more 'flat' compared to the old HD650 (old pads)


Now the old HD650 with new pads vs new HD600



Yes ... indeed the differences between HD650 with new pads (= close to new HD650 ?) and HD600 are pretty small.
Like Hans described just a very small difference in the lows and upper treble.


So to me the whole 'veil' thing can be attributed to FR related things.
THD and CSD is similar for HD650 old and new pads ...