There's a formula that will give you a good idea on the number of listeners you can support. It is:
# of listeners = .9*(upload speed)/(desired bitrate)
There is a page setup here
that will do the calculation for you.
Here is an example to make sure you put in the right numbers:
ADSL: 768down/128up (It is only upload speed you are concerned about)
Bitrate: 24 kbps
# of listeners = .9 (128)/(24) = 4 listeners
Of course this is assumming that you actually get 128 kbps upload and that nothing else will be using the upload bandwidth.
Fixed the link I messed up[\edit]
[This message has been edited by Tom (edited October 26, 2000).]