If you have never designed a speaker before I highly recommend that you use someone else's proven design. If you can acquire a complete kit that's even better. The typical process for designing a speaker involves setting a budget, deciding what the best basic application would be (bookshelf, floorstanding, etc.), choosing the appropriate drivers, designing an enclosure based on the mechanical and electrical measurements (Theil/Small parameters) of the drivers, designing a crossover, building a prototype, then measuring and adjusting before building the final product.