I love the warm and smooth sound signature of these phones. The upper region is also well-refined, but not emphasized in any way. These sound very smooth and relaxed, but not too laid-back. They can be quite energetic when the song demands it, and because of the smooth characteristic of the sound, these cause no fatigue over long listening sessions. Though they can cause physical pain to the neck, because they are very heavy.Otherwise these phones are very comfortable. The sound is quite balanced, but leans on the warm side of the spectrum. As with all planar magnetic headphones, the bass is thick and very audible. It doesn't overshadow anything or sound muddy. It sounds very natural and accurate. The best thing about these phones in my opinion is the mid-range. It sounds very full, lifelike and detailed. Vocals are sometimes so realistic that it scares me. Its like someone is singing right in your ear. Drums hit hard and you can hear how the strings are plucked on the guitars and other string instruments. These do good enough job with electronic music, but if that is all you listen to, then there are better options in the price range. For rock and other non-electronic genres, the mad dog is a clear winner in its price range. In my opinion of course. Some people might want more treble sparkle or more bass. But if you prefer organic sound over analytical or boomy sound, then these are the headphones for you.
Reviews by Im2spec1al
Im2spec1al
PSB M4U 1s and Mad dogs are both excellent headphones, you can't really go wrong with either one. If you're getting a headphone for home-use, you should also look into open headphones. Like Hifiman HE-400, Grados and Sennheisers for example. Although I think the Mad Dog- sound signature is pretty much perfect 
Willis
You are weak if you find Mad Dog heavy. haha
I have to say I'm leaning their direction...oh, the agony of choosing!