When we talk about the woofer surround and sensitivity, there are a few materials that are used, but the best subwoofers are always some kind of rubber. And this is so because the surround’s purpose is usually to reduce resonant vibrations that could distort the quality of the sound that is made. Lesser materials that are used for surrounds include the different types of plastic, especially urethane.
When it comes to the frame, this typically has to do with the heat expelling qualities than any other thing. Although low-end speakers will go with the less expensive plastic, that material easily traps heat.
Also, steel will trap heat as well, although this material is far more long-lasting. The best material for a speaker frame will be some kind of aluminum alloy that gives a solid structural durability while giving you a good heat dispersion.
This rating is quite more accurately noted as a rating of efficacy, but with it comes meaningful implications. For one, the more efficient a speaker is at being able to translate watts to sound, the cooler it will remain. This will enable the speaker to create sound for longer without needing to wear out the material components of the cone or surround as quickly.
The most important factor of a speaker’s sensitivity usually involves just how much power it would take to get a certain volume. Because of this, sensitivity is rated in decibels and it also determines just how many decibels a single watt is able to create. The more sensitive the speaker is, the less power the speaker would need to create any volume. So, in effect, two speakers that are of equal wattage but have varying sensitivity will favor the more sensitive speaker for its ability to produce more volume.
Subwoofers are made to play the notes at the lower registers of music. They have a much larger cone than the other types of speakers that allow them replicate the longer sound waves of bass notes.