The Mackie HMX-56 is a six channel headphone mixer, primarily designed for use in the studio. I only used one of these for the first time recently as I started working with a new producer who has this in his studio for headphone monitoring. I think that this is a somewhat new product from Mackie, but I'm not sure about this. Previously I had only used more traditional Mackie mixers for headphones, but perhaps they took the hint and designed one specifically for headphones. Each of the six channels has a 1/4" output for headphones and has four different input channels so you can control each person's mix separately. Each also has an overall level mixer and an effects return control. Another cool feature is that it actually comes with instrument labels so you can label each channel easily. Other connections that it has include 1/4" jacks for effects send and stereo return as well as 1/4" connections for the four source input channels and two 1/4" outputs for your mains. The whole "matrix" is pretty easy to understand and once you've got it set up you're pretty much good to go for a while. It's really the perfect little mixer for your home studio, although I'm not sure it would be ideal in larger studios as it doesn't provide remote access to the controls of your headphones mixes, so the engineer would have to dial in for each person. For larger studios I'd suggest something like the Private Qs if you can afford them, or even just getting a few traditional Mackie mixers to have at each station. Also, the price isn't too expensive as is usually the case with Mackie products. Overall, in smaller studio settings the Mackie HMX-56 is ideal and is a superb and inexpensive option for providing everyone with headphones mixes!