Thanks for the reply, guys.
The idea of "listen ssl" directive is to keep the configuration compact:
listen 10.30.1.50:80 default_server backlog=1024 rcvbuf=32k sndbuf=8k;
listen 10.30.1.50:443 ssl;

I only want to use SSL, in one directory. I know I can use the "long" method, my goal was to find out how I could do it in a compact form, like in my first post example. Thanks a lot for your help.