Aluminum is good material but a) need to be calculated to be low resonant and suitable for loudspeaker b) need dedicated tools, not suitable for DIY c) expEnsive. Natural Wood is good but only with heavy thk. Also need good practice and suitable tools. It is better to use playwood and MDF for DIY being easy to work, less expensive, good acoustic characteristics. It is perfect for final painting or to be dressed by low thk natural wood. In terms of constructability, it is preferable to use playwood for the bottom, front and top side and MDF for remaining panels. Reinforcements by playwood. No problem to glue MDF and playwood togheter as well final layer of natural wood if any. Please to consider that the real sonici part of loudspeaker are drives, crossover, wiring cable (internal and external should be adequate quality and dimensions) as well the cabinet should be heavy, strong, its very low resonance. Have a good DIY
