IIR Rubber surround used on loudspeaker

A surround’s quality has enormous impact on the frequency response of a loudspeaker. The shore hardness directly affects the frequency of the speaker. Rubber surrounds also endure a long lifetime, almost 20~30years. IIR rubber surround is ideal for car speaker and outdoor speaker as for its excellent seal property.
Some people say foam surrounds are ideal for sound quality and high excursion while rubber surrounds are slightly stiffer but they last longer. The cost difference between rubber and foam is pretty insignificant. There are so many other factors involved with choosing a speaker surround than just its surround type, for example magnet size and cone material, that the surround alone is not going to seal the deal. Both material types serve their purposes well, just take a listen to decide the ideal surround material.
Butyl, also known as Isobutylene-isoprene (IIR), is a synthetic rubber developed in the 1940’s. It has exceptionally low gas permeability making it ideal for inner tubes and high pressure/vacuum sealing applications. Its very low resilience makes it suitable for shock and vibration damping. IIR is a great option for shock absorption. It offers exceptionally low gas and moisture permeability and outstanding resistance to heat, ageing, weather, ozone, chemical attack, flexing, abrasion and tearing. Butyl is resistant to phosphate ester based hydraulic fluids and has excellent electrical insulation properties. It has a tendency to trap air, blister and creep during manufacture.