Double Helix Cables Molecule Headphone Cable - Reviews
Pros: I'll let the review answer this question.
Cons: None
New, 10' Double Helix Cable, headphone cables (Sennheiser HD-650 headphones) have arrived and here's my first impressions.
Flat, neutral, not as bright, loudness attenuated by 1-2db.
That said, my reference piece is K.D.Lang: "Hallelujah."
Lot's of piano chords, bass kick drum, subtle cymbals and an incredibly wide ranging voice.
I had to crank the volume an additional +2db to allow for the attenuation and switched out the cables a half-dozen times or so for what I considered a fair listening secession.  Even checked to make sure the new cables were plugged into the correct input (R/L) on the headphones.
My opinion:
Bass of the kick drum was more focused; less bloating.
The highs of the piano chords were smoother; no clipping.
Highs lack that harsh quality.
The piano is forward as opposed to recessed to the background and individual chords themselves are better defined.
The sound stage is wider and individual instrument placement is better defined by the additional sound stage width.
They look great on the computer table when not being used.
Yes, the cable's, in my book, a winner.
Did I notice a difference?  Absolutely as the flatness (neutral quality) of the new sound and the attenuation was hard to miss.  You also had to listen for the subtleties in the piano chords as they opened up by being more defined.  It was interesting to hear the tightening up of the kick drum; lack of bloating.  
In the end, would I recommend these cables to an innocent?  Absolutely not.  Why?  If they haven't a clue what to listen for, they're not going appreciate what they're getting and they'd be wasting their money.  I'd only recommend these cables to someone who appreciates the finer art of listening and even then, I'd recommend these cables only if you have the money to spend.
And lastly, to answer the unasked question, was it worth it?  If you take out the fancy sleeving ($10.00 USD/ft) and remove the cost of the splitter clamp ($25.00 USD/ea) from the total price of $380.00 USD, was it worth the left over $245.00 USD actual cost?  And the answer comes back.....maybe.  Why maybe?  Because it depends on how much you value the final sound quality of your music.  I value the final sound quality so reservedly, I consider it money well spent as the cables didn't lend a night/day sound quality upgrade but at this level, it's about the nuances.
Oh, and no I'm not going feed anybody's sickness regarding DBT's.  My recommendation to the anti-cable crowd, do what you will and be happy, I'll do the same.

Really fantastic cables! I just bought them for my LCD-2