Headroom question?

[A_M_P]

So from my understanding the finished beat (without vocals) needs to be at -3dB and THAT -3dB IS the headroom. My question is: to create this -3dB of headroom do you just turn down the master fader in the mixer to -3db? If so, how do you know when you are at -3db in Reason? because the volume levels in the mixer are measured by regular numbers; such as 1, 2, 3, 4, etc.

[cas1]

never touch the master fader..Leave it at unity..make a group channel and send all the channels used to make the beat to that channel..then just turn down the group channel til you have enough headroom

[LostProfit]

^Won't make a difference, especially not with software.

[A_M_P]

^Won't make a difference, especially not with software.

There is no difference in grouping all of the tracks than there is in just turning down the master fader? Is that what you meant?