It's very simple Mark.
It's up to you what type of frequency divisions you want to use because REW extrapolates between.
At the extremes REW will extend the last values.
If the mic reads low a negative value is entered and positive for positive.
You create a .txt file (with notepad) with frequency and decibel level. Then save the file and rename the extension to .cal
You'll have to decide from the graph what the values are.
For example here is a small sample of a cal file.
Code:
10.00 -9.23
12.50 -6.64
16.00 -4.68
19.95 -3.09
25.12 -2.08
31.62 -1.30
39.81 -0.83
50.12 -0.41
63.10 -0.14
79.43 0.00
100.00 0.15
125.89 0.22
158.49 0.22
199.53 0.26
251.19 0.26
316.23 0.26
398.11 0.22
501.19 0.20
630.96 0.14
794.33 0.07
1000.00 0.00
1258.93 -0.07
1584.89 -0.13
1995.26 -0.23
2511.89 -0.27
3162.28 -0.13
3981.07 -0.22
5011.87 -0.30
6309.57 -0.25
7943.28 -0.17
10000.00 -0.15
12589.25 -3.77
15848.93 -7.48
19952.6 -9.01
So decide what the vertical divisions on the graph are and use those values.
I would simply enter at the logarithmic values from the graph for the frequency divisions.
For example :
20 -2.00
30 -1.50
40 -0.50
50 0.00
60 (I'm sure you get what I mean):
70
80
90
100
200
create the file, and name it NT1.cal and load it into REW and see what it looks like. You'll see if it looks like your graph or not....
Questions?
brucek