John Piper is a Calvinist but listen to what he tells unbelievers from 4mins 40secs in on this video: https://www.youtube.com/watch?v=3psJWtT68WE&t=04m40s (The link takes you to 4.40)
"...embrace the gospel that Jesus Christ, the Son of God, the righteous one, died for your sins..."
The...