For the technicians out there...I'll be building my first bass cab in the coming weeks although I'm still tinkering with the design. I plan to use a normal tube to vent the cab. However, I did a little thinking about how tubes can influence the behavior of the air moving through them to enhance a cab's performance. My question is, would a concave-shaped port tube (concave inside and straight outside) enhance a cab's performance by throwing out low frequencies a greater distance? Has anyone ever "tried this at home" and come up with these or other results of any significance? The picture I have in mind is of a tube that looks exactly staight from the outside, but if you look inside of it, the inner walls decrease in diameter until the middle part and then increase for the remainder of the distance. Both ends would have the same diameter. So there's a slightly concave shape inside but the tube is straight outside. Here's how I arrived at this question. I have some books about aviation that I enjoy reading. These books describe how air interacts with a wing in flight. Wings are typically flat on the bottom surface and curved on the top surface, and air does moves faster along the top surface to meet the air coming from beneath the wing. There are a lot of factors that cause this, including static and kinetic energy, velocity, etc. I would think the same theory would apply when air and sound waves travel through such a tube design since the surface is similar to an airfoil. The only difference is the air pushed along the outside of the tube would meet the baffle towards the end of its journey, and not the outside. But I would think the air inside the tube would have a speed increase, resulting in a better throw? It might be far fetched, and I'm sure there are other factors to consider (possible tube noise, etc.), but am wondering if anyone has attempted that design in a production cab or on their own. Thanks!