I've created a Search Center site collection at mycompany.net/intranet (Enterprise Search template) and it worked just fine.
I've config to search in mycompany.net site collection, and it work OK.
when I go to setting, and choose Search Setting and specify http://mycompany.net/intranet in Search Center URL. Then I go back to mycompany.net and select search for everything,people or conversation, Instead of display the result, this page display like this.(If I choose This site, it work ok).