The Alpha Dog and Signature Pro/DJ leak practically nil if you are not blasting music up to very high volume levels. By comparison to both my TH600 can be slightly heard across the room from me listening to them, as long as the room has no TV/Radio or anything on. Sitting next to me you could understand the music. I believe I listen at a loud level compared to some on here, the AD or Signature headphones cannot be heard from even next to me when worn unless they were at very very high volume - which was too loud for me.
thanks for your feedback