I was curious to see what are the latest thoughts and what people are doing for designs of a subwoofer in a cabinet with closed doors.

What treatment is used and how the sub is isolated from the cabinet ?

We have in the past always cut out the floor of the cabinet and provide 4 inches minimum around the subwoofer.

We use anti-skid mats like the ones found under rugs on a hard wood floor to prevent
the sub from moving on the floor inside the cabinet.

Mostly curious what treatment is used if any inside the cabinet and a source for
acoustical foam to line the inside.

Thanks, in advance

Peter