How do I create a C# array using Reflection and only type info?

I can't figure out how to make this work:

object x = new Int32[7];
Type t = x.GetType();

// now forget about x, and just use t from here.

// attempt1 
object y1 = Activator.CreateInstance(t); // fails with exception

// attempt2
object y2 = Array.CreateInstance(t, 7);  // creates an array of type Int32[][] ! wrong

What's the secret sauce? I can make the second one work if I can get the type of the elements of the array, but I haven't figured that one out either.