One of the tricky parts of assembling an audio speaker is bonding the cone and surround—the parts that produce sound—to a metal frame.
The cone and surround are typically made of porous, low-energy materials, such as butyl rubber, Santoprene, paper or foam. The frame is usually made of cold-rolled steel or aluminum. Needless to say, the bond must withstand vibration. And, because the surround is one of the top parts of the speaker, the bond has to be cosmetic. If the speakers are mass-produced, the adhesive must set quickly.