Welker does the LT voices very well, but you can still tell its not Mel...
Uhh, Frank Welker didn't take over the Looney Tunes voices, assuming that's what you mean by LT. Since Blanc's death, they've been played by multiple actors. At first, Blanc's son Noel was slated to take them over, but for some reason WB went instead with impressionist Jeff Bergman, who didn't sound nearly as much like Blanc and was a poor actor as well. WB eventually learned from their mistake, and over the past couple of decades, various different people have played the Looney Tunes. Probably the best is Joe Alaskey, who usually does Bugs, Daffy, and Sylvester (including in
Looney Tunes: Back in Action) and has done many other Looney Tunes characters in other cartoons and video games. Billy West also plays Bugs a lot in various projects (including
Space Jam), and is usually Elmer Fudd (although Blanc only played that role once or twice; the original Elmer was Arthur Q. Bryant). Bob Bergen usually plays Porky Pig these days, Maurice LaMarche usually does Pepe LePew and Yosemite Sam, etc. (
Space Jam had a strikingly different cast from
Back in Action -- West as Bugs, Dee Bradley Baker as Daffy, Bill Farmer as Sylvester and Sam, etc.)
The only cases where Welker played WB characters originated by Blanc were in
The Sylvester and Tweety Mysteries, where he played Hector the Bulldog, and the movie
Tweety's High-Flying Adventure, wherein he reprised Hector and also played Hugo the Abominable Snowman and Mugsy the gangster henchman. Also, it's arguable that his Gogo Dodo character from
Tiny Toon Adventures was the same Dodo from
Porky in Wackyland.