quick summing resistor q

[gang of elk]

looking at NYdave's 8ch passive summing diagram, he uses 3.9k resistors. i *think* this is for 8-into-1, no?

based on this simple circuit, what is the relationship between # of inputs and respective resistor value? ie, for 4 channels do i double it? for 16 channels halve it? am i over-simplifying?

 

[gang of elk]

never mind, found my answer.

http://www.groupdiy.com/index.php?topic=2521&highlight=%2Amixer%2A

my apologies for waste of bandwidth.