The film company you’re thinking of is The Rank Organisation (often referred to as J. Arthur Rank).

What the logo looked like

  • A muscular man (the famous “Gongman”) stood in front of a huge gong.
  • He struck the large gong with a mallet, accompanied by a deep, resonant gong sound.
  • This sequence appeared at the start of films distributed by General Film Distributors and later The Rank Organisation from the mid‑1930s onward.

Extra bit of trivia

  • The gong in the logo was actually a prop made of plaster or papier-mâché; the real sound came from a smaller Chinese tam-tam gong played by percussionist James Blades.
  • The earliest versions featured boxer “Bombardier” Billy Wells as one of the Gongmen, becoming an iconic image of British cinema.

TL;DR: The “film company whose symbol was a large gong” is The Rank Organisation, famous for its Gongman logo at the start of its movies.