While there are many who debate this, it is generally agreed among the wider community that MDF (or Medium Density Fiberboard) is the best material for sub boxes. Essentially, this is because the wood is tough enough to work with, as well as ensuring there is no over-resonating sound – which can cause distortion and a poor experience. It can also stand the more extreme temperatures, which are likely to affect your car during the warmer and colder months, without breaking or bending.