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Each fEARful design has enough bracing in most circumstances to perform well. In fact the vibrational panel damping is better than found in most enclosures that are built out of 3/4" (18mm) plywood. But if one is using especially light or cheap plywood, or runs an incredible amount of power at lower frequencies - or just wants superior conversion of amplifier output into focused acoustic energy - then more bracing can be easily added to the integrated bracing design after the fact. In fact the bracing for fEARfuls was designed so that this would be easy and fruitful. The fEARful bracing style also makes the entire box stronger.
One way to determine where added bracing is most beneficial is simply to run program material with a lot of bass into the enclosure while feeling around on the outside of the panels. Then look at the example below and add bracing in the same approximate area. A Top Brace running from the side of the Midrange Chamber to the back panel is nice. It can reduce vibrations to micro/mini heads for one thing.
And one can extend Pillar Braces and Spine Braces in either direction usually, just by gluing in extensions. Make sure you glue at any adjoining surfaces (ie both the long area end any ends). It doesn't hurt to run a bead along the adjoining edges afterwards to make sure things are totally secure. If extending the Pillar Braces downward, leave around 3/4" between the top of the shelf and the bottom of the Pillar extension so that if one later wants to extend the shelf for a lower tuning that it is easy to slide a shelf extension in (see shelf extension article).
If the connector Cup Cutout has been located too close to vertical position of the Spine Brace one can not of course extend the Spine Brace upwards. But one can always add wood around the cutout where its screws go in. This can be a plate with its own same-sized cutout, or some runners 1/2" to 3/4" deep. That also gives the screws more to bit into and this all adds rigidity to the overall structure.
Likewise, one can put shallow plates over the Handle Cutouts, glued to the side panels and the adjoining Girdle and Pillar runs. If the Handles are shallow spring-loaded rack-case types no cutouts are needed in the plates, and that gives the additional benefit of ensuring a total seal of the handle area with no need for gaskets. And of course the screws that attach the handle have more wood to bit into. Do stuff some damping in between the spring-loaded handle and the plywood plate though - so that little cavity doesn't become a resonating chamber.
When the big big watts are trotted out it's amazing what a cab that was already solid sounds like, when one adds a little strategic bracing. A pound or less of additional bracing definitely increases the focus and acoustic output when one is really pounding things as hard as they can possibly be pounded. The enclosure still ends up being considerably lighter than the same construction would be if made of equivalent 3/4" plywood.
Adding bracing in the right places - further out in open panel areas nearer center - and not at panel-join edges and corners where it is wasted - is a good investment for any system that will be brutalized for maximum low frequency SPL. In fact I've often added bracing to commercial 3/4" enclosures - especially subwoofers and cabs with large open panels. It's a noticeable sonic improvement when the power gets poured on.
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