Polycom's founders solved speakerphone echo with a 95-cent RadioShack speaker-box book

In a first-person piece in Wired, Polycom co-founder Jeffrey Rodman recalls a March 1991 component run with co-founder Brian Hinman. They had decided to build an open-air audio system, a super-speakerphone, and needed a compact, distortion-free speaker. Their speaker knowledge came from hi-fi stores, and they assumed speakers had to be big. In RadioShack Rodman spotted a 95-cent book, Building Speaker Enclosures.

Rodman says its chapter on acoustic suspension was what solved the problem. A sealed enclosure creates two separate acoustic environments in a small space, one inside the box around the speaker cone and one outside where the microphones sit. He calls this isolation a breakthrough in the product's performance. They built the first physical model in a weekend from hobby-shop plastic panels, hot glue and an off-the-shelf paper-cone speaker, and paired it with algorithms that cancel echo and prevent feedback so both sides of a call can talk at once.

Polycom launched the SoundStation audioconference system in 1992. Rodman says it earned $1.4 million in revenue that first year and the company grew from two to 50 employees.

A speakerphone has speaker and microphones within inches of each other, so ordinary designs feed back.

A sealed enclosure gives the microphones an acoustic space separate from the speaker.

Echo cancellation in software made full-duplex talking work inside that physical design.

A cheap model built from scavenged parts let the founders test the idea in a weekend.

A cheap, old hobbyist reference can unlock a hard product constraint, so look at the fundamentals before inventing a new part.

Rodman, writing in July 2016, says revenue reached $100 million in 1998 and crossed $1 billion in 2008, and that Siris Capital had just announced its intent to acquire Polycom for $2 billion. These figures are the co-founder's own account, and the article does not credit the book as the sole cause.