MediaSpan is losing another top executive — the third in less than a week.

Jeff Williams, president of the radio division, said Monday that he will resign once the trnasition of MediaSpan’s merger with First is completed around July 1. The deal was announced last week at the same time MediaSpan closed on $4.5 million in additional venture financing and disclosed that its founding chief executive officer, Steve Vetter, had resigned.

“The First Media Works acquisition is the capstone of our radio new-media acquisition strategy,” Williams said in a statement. “With this deal completed, MediaSpan is now the undisputed industry leader, and I am proud of this accomplishment.

“It is bittersweet for me to leave at this time. However, with the new management this acquisition brought with it and my desire to pursue new opportunities, the timing is perfect.”

Williams was CEO of NextAudio when that firm and KOZ Software were forged to create MediaSpan. Other firms were acquired later. MediaSpan now has some 200 employees.

Sam Whitt, another executive with MediaSpan, announced his departure last week to return to law practice and to become a partner in Southern Capitol Ventures.