The Haas effect:
- If you take a signal and delay it by a very small amount, the brain won't realize it's an echo and will instead interpret it as being a separate sound. The threshold is in the 20-30ms range, according to most studies.
- For our purposes, this means you can take a single guitar track, pan it left, pan a copy of the same track right, delay the copy by 8ms, and it will sound like a double-tracked guitar part.
- It can, however, really mess up the mono image of your mix, which can become important a) if some jerkoff is listening to your masterpiece in mono, or b) if someone happens to be standing in just the wrong place with respect to their speakers. The two copies, being so close together in time, start to cancel each other out and sound really thin/shitty/etc. If it works for you, by all means, but it's just something to be aware of. Apparently some of the old Van Halen stuff uses it to fatten up Eddie's guitar.
- Personally, even though I don't hear it as a delay, the end result always sounds like it's leaning to whichever side the original is on. More delay = more width, but more of a pan effect. As such, if I do this, I'll usually do a real double-track and then give each of them a Haas so the stereo sound balances out.
- Longer delays will also start to cause problems if you're working with tight gallops and that sort of thing. However, if you set it to 1ms it won't sound very wide, so you'll have to do some playing.
For a free plugin, try this:
http://www.vescofx.com/vfxFreeHaas
You can also do it yourself with a delay. Using GDelay in Reaper, set up a 100% wet, 8ms delay, and then turn off either the left or right output pin. Boom, done.
Mid/Side Mastering:
- Some nerd, ages ago, figured out that by doing some fancy math with a pair of signals, you can separate the Mid (mono) and Side (stereo) components. Mid comes from comparing the two signals and taking the bits that are similar, while Side is derived from the bits that differ.
- For miking, this means that a pair of mics set up properly can give you left, right, and center signals to work with.
- For mixing, it means you can take a normal stereo mix/submix and tweak the center and sides separately.
- If you were to turn up the Side signal and leave the Mid alone, your mix would sound comparatively wider because you're accentuating the two sides. Likewise, turning down the sides will narrow the mix.
- You could also, for instance, turn down the low-end on the Sides and boost it on the Mids to tighten all of your lower frequencies in the middle of the mix, or maybe throw some reverb on the sides to give your mix a sense of space.
I've read in a few places that, rather than focusing on width, it's better to make sure that the stereo spectrum is fully used - give every instrument/drum its own combination of pan position and frequency range so everything has a spot to sit in, things aren't fighting with each other, and so on. I try to leave width tricks until after I've got that sorted out, which tends to be never, so... yeah.