Port Material

My cabinets have a have a slot-in 50x50mm port resulting in a tuning frequency of 55Hz. Here's a thing . . . if a slip a toilet roll centre over the port (it's a really snug fit), it lowers the tuning frequency to 42Hz.

But let's face it, toilet roll centres are thin and flimsy. Why do I need something more substantial?
 
Are we going for optimal for as little cost as possible😱?

Hit up an industrial print house, for scrap cardboard tube rolls. Small to large, tougher tnan cement forms. They come small to large.

The empty shrink wrap toobs are great for this application also, if the sizes line up. Rolling a car over them wont bend them. There super strong:magnet: 😱

PVC pipe is another good next el cheapo option. Often you can find that free.
 
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