Three Part Harmony Doubles Panning

Well the main vox should stay centred, the harmony vox's should be panned hard right and left.  You should EQ the main vox as you would normally, so for a main vox I would give a boost in the higher end cut the low end and then find the formant of the vocal and boost slightly.  You would do the opposite to the harmonies.  You could also try different reverbs on the harmonies and you could even chuck a little bit of chorusing on the harmonies too.  Just to thicken them and differentiate them from the main vox. 

Double Post

I use doubling and harmony a lot. 
 
My song Missing Person (2012) http://www.soundclick.com/bands/page_songInfo.cfm?bandID=443134&songID=11962059  has 10 vocal tracks.  2 singers with 1 main and 2 doubles and 2 harmonies each.
 
Footsteps has 5 vocal tracks http://soundclick.com/share.cfm?id=12048139
 
On any given project my average solo project has 5 vocal tracks in the end mix.  One is lead. the second and third tracks are also lead vocals that have been recorded live, never cloned. I keep the main vocal centered and about -6db but that level really depends on the way it sets in the mix. No FX in the track. Set up a vocal bus for reverb and EQ with all 3 leads going there. Pitch correct the lead vocal track and perhaps the doubles. The key to avoiding the flangy, phasey sound is to pan the 2 doubles wide..... 80% or more and keep the levels on them somewhere around -24db. This level will be set by trial and error but -24 is the starting point.  My aim is to let these tracks add a slightly fuller sound without being obvious. In other words, I can't really hear them in the main mix, but if I solo the vocal bus I can hear the doubles.
 
On the fourth and fifth tracks,,,,,, harmony tracks, these too are recorded independently. I pan them 50% to 80% in most projects and use -16db as the starting point.  I want the harmonies to "fill in" the vocal in the chorus and other places where I have them. Generally, I like a subtle harmony presence. You do have the choice to bring them up and create a "Statler Brothers" kind of harmony where all the harmony vocals have equal billing in the sound stage. I do not generally like to use that method of harmony but will do it as the song demands. I also will very often put the harmony tracks in their own bus and add a slightly heavier reverb to them. Nothing crazy, just something that moves them "back" a bit.
 
This is how I record vocals and harmonies. If you clone the lead, you will have exact duplicates of the tracks and more issues with comb filtering and for that reason I always record independent tracks. Even so, I have to be careful to avoid the comb filtering that is possible with three very similar tracks. Keeping the levels low on the doubles will help immensely in that area. It still gives you the fatter doubling but at more of a subconscious level and it leaves the main vocal sounding cleaner.  To see if you can hear the difference, simply use the GROUP function to group both of the doubled/panned vocal tracks and then as the song is playing in the parts where there is not harmony vocals, use the mute to mute and unmute the 2 doubles during playback.
 
Anyway.... that's how I do it. hope this helped you.

Don,
 
I record and handle layers of vocals and harmony's almost identical to the way Herb does.  The only difference is in my panning of the main vocals.  Lead vocal is always dead center.  I usually do 2 other layers and pan them anywhere from 35% left and right up to 100%; it all depends on the song and how the other instruments are panned in the song.  I listen while panning and have them find their own space within the mix to sit.  It's all about competing space for me.  
 
I always record separate takes of vocals and sing them as closely to the lead vocal as I possibly can, for layers.  Most of the time I will tweak pitch and timing on those layers.  The key is to get them as close to the lead as possible, but still be different enough to sound good.  Again, it is an ear thing.  Levels are pretty similar to Herbs.  Depends on how much you want the layer or harmony to be noticed.
 
Another trick that I have used on a layered vocal is to automate volume so that the vocal layer is not always present, but comes in on certain phrases, groups of words or a particular word that you want to emphasize; that can be really effective.

These observations are troubling:
 
    It sounds a little "flangey" to me at the moment.
and
    I believe I've ran into my first real encounter with comb filtering...
 
I believe your diagnosis is correct: you are hearing phase issues.
 
Normally, you'll only have this problem if you're mixing cloned tracks, because they're identical to the original except for delays or other effects that affect their phase relative to the original. However, I have also run into it when the tracks were not clones but were overly processed with Melodyne, V-Vocal or AudioSnap. 
 
One kludge that'll help disguise comb filter artifacts is to apply a chorus to the cloned tracks. Another trick is to roll off the highs on the clones. Only the primary track needs to convey consonants, so you can tolerate some loss of intelligibility on the reinforcing clone tracks. You might also be able to alleviate the phasey effect by nudging the clones a couple of milliseconds.
 
 
 

Another approach is a widener on the BGV group to get them out of the middle. I have also seen them panned at 50/70/90 for each vocal harmony. 100% L & R is reserved for delays and fx in a modern mix to keep things out of the center, unless a mono fx is used. This is a recent trend and not universal.

Jim Roseberry
The "Nashville" approach for tracking background vocals is to triple-track each harmony part.
Roughly speaking, one take is panned left, another right, and the third is up the middle.
While tracking, session singers often want to hear the first take panned left in their cans (while they're recording the take that will be panned right).
This allows the vocalist to focus on and adjust to the nuances in the first take (to match closely).
 
With three-part harmony triple-tracked, you get that nice full/wide (group) background vocal sound.
 

For my last two efforts I double tracked and did some panning with each part.  I'll try a triple next time.  Track templates make this easy peazy.  I'm so enjoying all this.
 
Donny

Well last evening I did my first triple track on a part.  It was single line, tracked three times, panned center, hard left and right.  There was another two tracks an octave higher panned a little left and right.  It's on the intro of this tune:
 
https://soundcloud.com/donny-collins/carry-to-my-love-blessed-union
 
Only compression and low cut at about 200 hz on the lower octave.  Did one take of each track, took maybe five minutes.  Like it alot.  I've got a track template setup for my mic/pre, so it's really easy to add takes.  I'm sure there's an even easier way I've not used yet.
 
Copy that on the phrasing and blend...that is key and I'm careful about that.  That's where paying close attention in high school choir comes in really handy.

i love the stones' backups on the older songs...
 
and they RARELY said anything together!
 
LOL
 
so, just goes to show you, vibe always trumps dead-on accuracy
 
check out some of Rundgren's vocal panning on 'something/anything'
 
 

yea, i don't really care for that stuff.
 
too stiff.
 

batsbrew
 i NEVER copy performances. i do not like the sound of that at all. i have found that when i sing with myself, i cause phase issues because i sing so close to the original (not saying i sing well, but sing consistent) and the ADT effect seems to compound that problem.

I'm the same way. I won't copy tracks, yet when I double or triple vocals, it tends to cause phase issues. Usually once I settle on a vocal style and melody, I don't deviate at all. So I'll put lead 1 straight up the middle, then put lead 2&3 about 35% left and right, but with the levels down so far that they're just fattening up the main track. Then BG vox I'll double each harmony and place those 80% & 100% left and right. And I absolutely NEVER use V-Vocal on ANYTHING. I despise that thing. I have enough trouble avoiding phase issues on vox without throwing that thing on top of it.

I used to use melodyne actually.  I'll have to dig it out and see if I can make it work...I don't recall if I was 32 or 64 bit at the time, but I loved the interface.