First, let's take a look at where the violins, violas, cellos and basses normally sit in the the orchestra.
Now, here's where things get tricky and particular. In my previous post on winds I mentioned that sticking to the orchestral layout is a desirable place to start. However, when mixing strings, I tend to throw that convention out the window.
Violin I on the left (like in the orchestra)
Violin II on the right (like how orchestras used to be)
Violas center left
Cellos center right
Basses in the center
Why on earth would I do this?
Good question. To me it's more about having a modern sound with my orchestral works as a starting place. Having violins hard panned to the sides helps create a balanced listening experience (especially since they are often playing similar musical ideas) and having basses in the center is how most modern recordings sound. Especially if you bass is big sounding (like many film scores) having it be lopsided would sound very odd.
Okay, so that's how I mix stereo. But what about 3D?
When I was doing my masters thesis on binaural orchestral mixing, I tried to visualize how I wanted the orchestra to sound. I came up with this.
I like to put the violins in the top right and left hand corners respectively. They can't go lower than a G3 on the keyboard (196Hz) so even if they are at their lowest note they won't sound too strange. You can also mess with the panning if they spend a lot of time in the lower register.
Bass and Cello at the bottom (think chin-level rather than below). Notice how it goes all across the horizontal spectrum. Bass instruments tend to blend well together and have a 'wider' sound. Also, as humans our brains have a difficult time registering low noises above our heads, it's just no something we're used to.
I decided to place the viola center right (could also be center left) for two reasons...
1) The placement of the violins, cellos and basses leave a nice gap in the center (also for winds).
2) Lots of room for movement. Violas tend to have very interesting lines, jumping between supporting the violins and cellos. This allows it to easily be moved around depending on which instrument it is supporting. It can also be moved to the direct center if needed for a solo or if you want to double with the cellos. Try to keep the movement to a minumum though to avoid any confusion.
Strings are definitly the driving force of an orchestra, so ensuring that you get the balance right is paramount to making the orchestra sound good as a whole. Hopefully this is a good starting point as you explore binaural orchestral mixing.