The spider is usually made of a corrugated fabric disk, generally with a coating of a material intended to improve mechanical properties. Unusually, a German manufacturer, Klangfilm, used bakelite for spiders in some of its early drivers, and another German company currently offers a spider made of wood. The surround can be a roll of rubber or foam, or a ring of corrugated fabric (often coated), attached to the outer circumference of the cone and to the frame. The choice of suspension materials affects driver lifetime, especially in the case of foam surrounds which are susceptible to aging and environmental damage.
Designers can use an anechoic chamber to ensure the speaker can be measured independently of room effects, or any of several electronic techniques which can, to some extent, replace such chambers. Some developers eschew anechoic chambers in favor of specific standardized room setups intended to simulate real-life listening conditions. A few of the issues speaker and driver designers must confront are distortion, lobing, phase effects, off axis response and crossover complications.
