The strengths of materials commonly used in mobile audio applications span about one order of magnitude, as seen in Table 1, with MDF at the low end of the spectrum and low-carbon, cold-rolled steel at the high end. A reasonably sophisticated but widely available alloy, 6061-T6 aluminum, possesses about the same strength as low-carbon, cold-rolled steel. In addition, the data in Table 1 clearly illustrates that a fiberglass composite comprised of woven roving is essentially twice as strong as a fiberglass composite comprised of chopped strand mat. Again, this demonstrates the significant advantage of using woven roving wherever possible, to create the strongest possible structures. Baltic Birch plywood is 25 percent stronger than MDF, and a fiberglass composite comprised of woven roving is about six times stronger than MDF.
The densities of materials commonly used in mobile audio applications also span about one order of magnitude, with Baltic Birch plywood at the low end of the spectrum and low-carbon, cold-rolled steel at the high end in Table 1. Interestingly, fiberglass composite materials are about twice as dense as those materials derived from wood.
The specific strengths and specific stiffnesses of materials commonly used in mobile audio applications are also in Table 1. Steel has the highest specific stiffness, while a fiberglass composite comprised of chopped strand mat has the lowest. Aluminum and steel have similar specific stiffnesses, but aluminum has the highest specific strength, more than 2.63 times that of steel. Interestingly, the specific stiffness of Baltic Birch vastly exceeds that of a fiberglass composite; however, a fiberglass composite comprised of woven roving has the second highest specific strength. From this data, a few important conclusions can be made. First, if the best combination of strength, stiffness, and lightness is your goal, choose aluminum for your application. If stiffness and strength is your goal, without regard for weight, choose steel for your application. If your application requires the creation of "free-form" 3-D shapes, choose fiberglass composites comprised of woven roving. Finally, for your loudspeaker boxes, choose Baltic Birch over MDF whenever possible.
List of Terms
Stiffness
Strength
Stress