Sperling died in Boca Raton after a lengthy illness ... according to his spokeswoman, Terri Lynn.

Sy's career path began being forged in the late '60s when he was a balding swimming pool salesman in New York City who'd grown tired of wearing toupees.

So, he took $10k in credit card debt to open a Madison Avenue salon and used a hair weaving technique he learned from a stylist to implement a system where a nylon mesh cap was glued to a person's scalp ... allowing their hair to grow through it, then additional matching hair purchased from women was woven into the mesh.

Sounds pretty odd, but business took off ... just not to the point where Sperling wanted it to be. Enter, the TV commercials.

Sy began advertising his hair replacement system on TV and went national in 1982, with spots running 400 times daily on late-night TV. They reportedly cost $12 million a year but generated 10,000 calls a month.

The ads featured before-and-after photos of happy customers, but ended with Sperling himself proclaiming ... "I'm not only the Hair Club president, but I'm also a client." They became a cultural phenomenon almost instantly.

The company's now simply referred to as Hair Club and began offering services for women in 1995. Sy retired in 2000 after selling the company for $45 mil. It's helped more than 600,000 clients restore their hair over the years.

Sperling is survived by his wife and 2 kids.

He was 78.