OK please bear with me on these questions but like many others I find a lot of conflicting advice around. #1 How good is WinIsd at helping to design a good cabinet for bass. What are it's limitations and are there better programs out there? Also which version is best? Beta or Pro alpha. #2 I have always believed that it is best to get the most efficient driver possible. However some of the speakers recommended on here and elsewhere have great XMax figures but poor sensitivity. I realise that sensitivity is measured at 1KHz usually but even looking at the response graphs the sensitivity of many highly regarded drivers is in the mid 80s at 50Hz. Discuss! #3 Vents/Ports. I am happy to have any type of port but I am confused. Is a shelf port different to a slot port? I thought that ports should be kept away from the cabinet edge but a shelf port uses the edge. Can anyone shed some light (sound) here? #4 Driver unloading. I think this is where the tuning stops working and the drivers sees an open baffle. It sounds dangerous for the driver so is there a formula or rule of thumb that says what frequencies are affected? #5 Xmax. I assume that this is the maximum linear travel of the cone/voice coil. At what power is this reached? Again is there a formula or way of calculating this? Sorry for the long post but the more I look into this the . more confused I get.