SoundMAGIC doesn't need to be amped for its sound, but it helps. Using a proper amp, you get additional details, much needed texture, a wider soundstage. It doesn't just go up in volume, but it also scales nicely with the amp. The headphones feature a very balanced signature that doesn't need to much burn-in to get the proper experience. There is a difference though, and after about 10-15 hours of use, the signature changes slightly, gaining even more volume.
As for the sound itself, HP150 could be described as neutral sounding. It doesn't become too bright with not enough bass behind it, nor does it use a skewed V-shape signature with a bloated low-end. No, instead it relies on a warm, detailed, and clear sound.
It features a much wider and deeper soundstage than closed back headphones like the M50x or VMODA XS.
As for the sound itself. These are very neutral sounding headphones, with an almost flat response curve. As such, these headphones is quite interesting in the department of closed-back headphones. It has a much nicer sound-stage than M50x, and at the same time, while the bass is not emphasised, it has a surprising tightness and punch behind it, which is always nice. There's also a surprising amount of details you get to hear, and it's especially interesting when it comes to vocal and nuances to the voice of musicians.
The bass has a surprising tightness behind it. I prever the HP150 over the M50x, only because it has a lot more detail and texture, and the kick is quite pleasant. Tracks like Dido's Let us move on, show a very deep and extended sub-bass. Mid-bass doesn't fall behind, it still has a very nice kick to keep the flow going. However, it's worth noting that if you listen to these headphones on an un-amped source, much of the bass texture as well as the quickness is gone.
The bass transitions smoothly into the midrange, with no bleed from what I heard. Mids, especially the upper ones are exceptionally detailed, and carry a great of brightness, even though it doesn't end up sounding sharp. It stil manages to keep a full body without becoming overtly colored or way too warm.
I do enjoy HP150's treble. It's clean, nicely extended and carries the same amount of details as the mids. There's a lot brightness, but no hint of sibilance, which makes it pleasant to listen to, without it becoming too hot or too sharp. You could listen on the headphones for hours, and it won't cause any listening fatigue.
I feel SoundMAGIC has delivered a very spacious sounding pair of headphones. For a pair of closed-back cans, HP150 has a soundstage matching some semi-open cans like the Fidelio L2, whilst hovering above similarly priced over-ear headphones like the M50x or the V-Moda XS.
Not only that but the layering and separation is exceptionally transparent, allowing you to hone in on an instrument and pinpoint its relative position.