Hi - I too am having beats related trouble with new Envy-17, see
I'll try the fixes listed above but I thought I share a some screen shots I took from another HP laptop (and Elitebook 8560w) - it's a "business" model so it comes with the SRS branded stuff not Beats Audio - but as you say, they are basically the same. The point is that you can disable SRS - and the headphone audio is good,
the fact that this works in SRS and not in the Beats version means that its just a bug, and it can be fixed with a new driver.