Speck Mellencamp -- Surrenders to Cops After Alleged Porch Beating

Speck Mellencamp -- the 18-year-old son of singer John Mellencamp -- has turned himself in to authorities in Monroe County, Indiana in connection with the brutal porch beating of a 19-year-old man.

Speck -- along with his 19-year-old brother Hud and their alleged accomplice Ty Smith -- have all been charged with felony battery after allegedly unleashing a ferocious beatdown on a man who was sitting on his own front porch.

As we previously reported, the victim claims all three men attacked without warning ... and stomped, punched and kicked him ... resulting in a several facial fractures.

The victim claims Speck threw the first punch.

FYI -- Ty Smith is the son of Indiana University baseball coach Tracy Smith.

Both Speck and Smith have been released from custody on $5,000 bail.

As for Hud, we're told he's expected to surrender to authorities sometime tomorrow.