The HE350 sound impressions are mainly for anyone wanting a point of reference regarding how they more or less pair with the iPhone 6, QP1R and Surface Book. Other sources may vary slightly or greatly as the HE350 sounds different enough with these three sources to warrant mentioning. The HE350 will have a warmer and pronounced effect in the overall bass region when pairing with the iPhone 6. The HE350 will have a supremely detailed with slight treble and bass with extended detail when paired with the QP1R. The HE350 will have a more balanced and natural sounding approach to its presentation when paired with the Surface Book. For reference, the HE350 is fairly easy to drive, as a smartphone such as the iPhone doesn't take full volume for the HE350 to emit levels that can damage hearing pretty quickly.