maverickronin said:

Headphones are a lot more personal than the rest of the associated audio gear so it's harder to make a recommendation.  Headphones are full of far more compromises than amps, DACs, or DAPs and given differences in anatomy between different users and the inherent unnaturalness of listening to recording mixed for stereo speakers over headphones I don't believe it's possible to even construct a theoretical model of a perfect headphone.

I've never heard them, but Tyll at Innerfidelity has measurements of the Superlux 668B and 681 along with your current Sennhesier HD439.  The most obvious difference is that the two Supeluxes have a lot more treble than you Senns which may or may not be what you're looking for.  The Senns seem kinda dark anyway so I'd say the Sperluxes are closer to neutral in that regard.  Less obvious but even more important for some people would be the sharper ringing on the square waves of the two Superluxes (especially the 668B) which often indicates driver ringing in the treble region which can be fatiguing to many people.  OTOH, the 681's frequency response compare very favorably to the electrostatic Stax SR-207s.  The 207s destroy the 681s in the distortion and noise department though.

Overall I'd guess that the 681s would be a better choice than the 668B because of a more neutral frequency response and less driver ringing in the treble region.  Picking between the 681 and the HD439 is a matter of preference though.  The 681s will have a more 'reference' sound but many people will also be fatiguing to listen to for long periods whereas the Senn isn't as neutral and might have as much detail but will probably be easier to listen to for hours on end.

In the end a lot of this is preference.  I put a lot of emphasis on possible harshness or ringing in the treble since that really bothers me and limits my headtime with a 'phone regardless of it's other virtues.  For example, I prefer the HD650 to the HD800 since the 800 has a bit of that kind of treble issue (which the 650 completely lacks) even though the 800 does everything else better.

Also to reiterate, I haven't heard the HD439, 668B, or 681 myself.  I've just outlined the kind of analysis I'd do if I were considering buying them myself and hadn't heard them.

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ruben123 said:

But how do they actually "hear" it, is the next Q.
A sharp edged, piano colored dap sounds different from a grey one which is 3x as big, has all sorts of real dials and no screen...
But how?

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cel4145 said:

For instance, lots of people believe that they can hear significant differences between lossless audio (e.g. flac or wav), and the same music file then encoded in high bit rate AAC or MP3. But ABX testing where the person doesn't know which file is which has shown that most people can't tell a difference. Try it yourself if you have not: http://lifehacker.com/5903625/mp3-or-lossless-see-if-you-can-hear-the-difference-with-this-test

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bufferoverflow said:

 

cel4145 said:

For instance, lots of people believe that they can hear significant differences between lossless audio (e.g. flac or wav), and the same music file then encoded in high bit rate AAC or MP3. But ABX testing where the person doesn't know which file is which has shown that most people can't tell a difference. Try it yourself if you have not: http://lifehacker.com/5903625/mp3-or-lossless-see-if-you-can-hear-the-difference-with-this-test

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The operative word here is 'most' - Because some people CAN reliably hear the difference, leading to the conclusion that there IS in fact a difference .

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bufferoverflow said:

  No, you don't "pick" anything, you convert the same music to 2 formats .
Try it with some Bach organ-music .. Or any decent recording of real instruments for that matter .
Some people CAN reliably tell the difference - There IS a difference in some cases and nullsumming proves it .

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bufferoverflow said:

  No, you don't "pick" anything, you convert the same music to 2 formats .
Try it with some Bach organ-music .. Or any decent recording of real instruments for that matter .
Some people CAN reliably tell the difference - There IS a difference in some cases and nullsumming proves it .

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bufferoverflow said:

The operative word here is 'most' - Because some people CAN reliably hear the difference, leading to the conclusion that there IS in fact a difference .

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bufferoverflow said:

  No, you don't "pick" anything, you convert the same music to 2 formats .
Try it with some Bach organ-music .. Or any decent recording of real instruments for that matter .
Some people CAN reliably tell the difference - There IS a difference in some cases and nullsumming proves it .

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uchihaitachi said:

  Has there actually been a single documented case of somebody significantly telling the difference between a 320kbps mp3 to a lossless format?

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rrod said:

 

uchihaitachi said:

  Has there actually been a single documented case of somebody significantly telling the difference between a 320kbps mp3 to a lossless format?

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This guy seemingly can:
http://www.head-fi.org/t/755650/what-does-science-think-i-should-buy-in-the-head-fi-market/405#post_11496984
 
Though my current attitude towards ABX is that one should do it for ones-self, and never trust online results.

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rrod said:

   
This guy seemingly can:
http://www.head-fi.org/t/755650/what-does-science-think-i-should-buy-in-the-head-fi-market/405#post_11496984
 
Though my current attitude towards ABX is that one should do it for ones-self, and never trust online results.

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sonitus mirus said:

   
If the files are equal with regards to amplitude and phase with exact starting and ending points, I've not seen any reliable evidence to suggest that anyone can tell a difference.  All of the controlled tests that I have read about, and that provide details about how the test was conducted, seem to indicate that it is nearly impossible for anyone to be able to hear a difference.  It is exceedingly rare to find anyone without an agenda of some sort that can pass an ABX test successfully, and even in these personalized and unconfirmed test cases, it is quite possible that the equipment is suspect as even fewer tests have upsampled the lower quality file to be the same format with regards to bit-depth and sample rate.
 
It's not as if "Scott and I can't tell a difference, but Brian can", which is how it comes across when people claim a difference can be heard by some people.  The differences are exceptionally subtle it would seem, based on those few claims by people that have shown that they are able to hear a difference with these improperly monitored tests.

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