My buddy Dave builds custom speakers as a hobby. He never uses the cross-bracing inside the cabinets that all the forums swear by. Just glue and good joints. We gave one a good shake test, and honestly, the thing felt totally solid. Makes you wonder if some steps are just for peace of mind, not because the thing will actually fall apart.
Dave's shake test sounds CONVINCING, @coletaylor. But has he tried blasting deep bass tones through them? I've heard that without bracing, large speaker panels can vibrate and mess with the sound clarity, even if the box feels rock solid. That internal shaking might not show up in a hand test but could ruin the audio quality.