Planar

This alignment is similar in concept to a "clamshell" or face-to-face isobarik and will behave in a similar manner, but it also has some of the detractions of the tunnel-loaded isobarik that are associated with having a coupling chamber between the two drivers. It is somewhat space-inefficient in that you are giving up usable space behind the outside driver, but it produces a very interesting visual effect if you put a sheet of plexiglass in front of the speakers.

Construction tips 2kB GIF

The loading chamber (indicated by the pink shaded region) should be between 0.75" and 1" deep. You should also do everything possible to minimize the surface area of the loading chamber since any trapped air in it essentially becomes part of the moving mass of the speaker system.

If you are more industrious, you can round off the ends of the loading chamber as seen in the diagram at right.

If you intend to utilize a ported design, port lengths can be rather large. This is common with single iso-group enclosures because of the small box volumes. For this reason, you may want to fire the port as shown in the diagram below. This should allow you to extend part of the port tube outside the enclosure without it being visible, however using JL Audio's Flex-Port will allow you to use such an enclosure without ugly protruding ports.

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The only thing you need to watch out for is that the inside mouth of the port is at least 4" away from the opposite wall of the box and that the outside mouth of the port does not fire directly towards the cone of the outside speaker. As a last note, the outside speaker needs to be wired in reverse polarity so that the cones move in the directions indicated by the arrows in the first diagram.