Wharfdale did the sand. Bozak's claim to fame was infinite baffle speakers. There are lots of sub kits out there now and if you have some woodworking experience and some basic tools by all means. Dayton makes a very advanced plate amp with room control.
It is extremely difficult to control resonance in box speakers. The kit manufacturers because of weight limitations and cost to not dig very far into the problem. If you are capable, making your own enclosure is the way to go. Calculating volume is easy once you know your driver's parameters. It is just plug in math. Tricks to control resonance are first use very thick walls. In MDF 2 inches minimum. Keep the sides, top and bottom as narrow as possible but make the top and bottom wider than the sides are tall so that they resonate a different frequencies. You want to make things so stiff that the cabinet resonates at a frequency as far above the woofers cut off point as possible. The heavier the better. You do not want the whole cabinet shaking. Always three spiked feet and right into the floor. No pads. Ideally with the woofer pumping out it's lowest frequency you should feel nothing with your hand on the enclosure. Any movement or vibration that you feel is distortion. You will never feel a commercially made sub that quiet with maybe the exception of the big Magico subs. Get a piece of granite cut to size and silicone it to the top of your enclosure. The added weight always helps and you can get granite cut offs for cheap. I prefer external amps and cross overs. JL Audio makes a nice external crossover.
It is extremely difficult to control resonance in box speakers. The kit manufacturers because of weight limitations and cost to not dig very far into the problem. If you are capable, making your own enclosure is the way to go. Calculating volume is easy once you know your driver's parameters. It is just plug in math. Tricks to control resonance are first use very thick walls. In MDF 2 inches minimum. Keep the sides, top and bottom as narrow as possible but make the top and bottom wider than the sides are tall so that they resonate a different frequencies. You want to make things so stiff that the cabinet resonates at a frequency as far above the woofers cut off point as possible. The heavier the better. You do not want the whole cabinet shaking. Always three spiked feet and right into the floor. No pads. Ideally with the woofer pumping out it's lowest frequency you should feel nothing with your hand on the enclosure. Any movement or vibration that you feel is distortion. You will never feel a commercially made sub that quiet with maybe the exception of the big Magico subs. Get a piece of granite cut to size and silicone it to the top of your enclosure. The added weight always helps and you can get granite cut offs for cheap. I prefer external amps and cross overs. JL Audio makes a nice external crossover.