Ok, so my mind is a little hyperactive and I find myself doing whatever I can to keep it occupied, sometimes that involves math.
Long story short, measure the difference in distance from your speakers to your listening position. Calculate the difference in distance from the furthest Speaker to all the others and divide by 13.4 if you measured in inches or by 34 if you measured in CM. The result is the delay in ms that you need to properly setup your time alignment.
Read on below for an in depth discussion of how I came to this.
For example lets say you have a 3 way front stage plus sub and your distances are as follows (in inches)
L Tweeter 24
R Tweeter 33
L Mid 26
R Mid 32
L Midbass 22
R Midbass 23
Then you pick the furthest speaker, in this example that would be the Subs. They will be 0 adjustment on time alignment. So you need to know how much closer these are than the subs, so you can digitally delay them so they appear to the ears as being exactly as far away as the subs.
So you take the 45" the subs are away from you and subtract the distance for each given speaker, this will give you the difference.
L Tweeter 21
R Tweeter 12
L Mid 19
R Mid 13
L Midbass 23
R Midbass 22
Now here is the really easy part..... Simply divide by 13.5. That will give you the delay in ms that you will need to enter. If you are one of those types that likes the metric system, and you just had to measure everything in cm simply divide by 34. How did I come to this math you ask? The speed of sound is 1115 ft per second, and 340 meters per second (rounded the numbers to make them a little easier to work with, a difference as little as this will make less than 0.01ms difference in the end result).
Since speed is distance/time (miles per hour, meters per second etc) we can flip that equasion around to get time. That formula would be time=distance/speed. So we now know the distance and the speed we can calculate for time. To get results in the units we need, we need to convert the speed of sound to either inches per millisecond, or centimeters per millisecond, depending on which measurement system you use. To convert 1115 feet per second to inches per ms, we first multiply by 12 to go from feet to inches, this gives us 13380 inches per second. To go to milliseconds we simply divide by 1000. That gives us the much easier to work with 13.38 number. I use 13.4 for a little simpler calculations. Similar calculations can be made to convert from 340 meters per second to inches per millisecond. Meters to cm you multiply by 100. Seconds to ms you divide by 1000. This gives us 34 cm per second.
I had not read anything that gives as easy of a calculation so I thought I would share this in the hopes it would benefit others.