I posted pictures of my sanding table at
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that works. In the closed picture note the velcro patch on the left front of the top. That is what holds my sanding curtain which directs air from the lathe to the air cleaner. The furnace filters are 14 x 25. The cloth bag filter is labeled 12 x 24, but measures11 1/2 x 23 1/4 at the top frame.
I use it mostly as an air cleaner to catch what escapes the dust collector, but it works well as a sanding table with the top down. I calculated the total square inch of the holes to equal the area of the exhaust port.