That's good to go with.
I use the numbers 300 to 3000 because they're easy to remember, but the real numbers are much closer to his. Voice transmission may not go higher than about 2400 because 2600 is the pitch that telco management signal tones use. Manipulating tones at 2600 will cause odd things to happen on a phone, hence the hacker journal named "2600 Magazine."
You can get production variations by adding noise before the equalization step and by tilting the graph upward on the right.
Cordless phones get "SH" sounds sprinkled around and, of course, cellphones get gargly and drop out. You can get the cellphone gargly artifact by exporting your track to a very bad MP3 and then switching back and forth as you "talk."