6 of 9Image
HP Spectre Beats Audio controls
Both devices are Beats Audio branded, making for a fair comparison on audio.
The Envy 14 Spectre uses a dedicated jog wheel for volume control and hardware buttons for quick access to the Beats Audio software, whereas the DM4 uses keyboard shortcuts accessible via the function (fn) key. There was another small difference between them on audio: DM4 came with a set of over-the-head style Beats Audio headphones included in its price too, the Spectre did not.
That's where the obvious differences stopped: neither sounded notably better than the other, although both were louder than other similar sized laptops that I've used.
Image credit: Ben Woods