Originally Posted by cessna1466u
I just received the Klipsch subwoofer and of course it has the loose port tube. I am going to take it apart to fix that and while looking at some ideas on how to fix it I came across some posts about people making braces for their subwoofers internally. I am pretty crafty with wood and I am sure I can come up with something that will work with this subwoofer, my question us has anyone done it and seen an improvement? Or is it even worth it? I am already going to put in some polly-fill and taking care of the loose port issue. Should I just leave the bracing out of it?
An enclosure has to be pretty small to not benefit from cross bracing.
When I build enclosures, I perform "rap testing" I give a robust knuckle rap to the the unsupported middle of large panels. If it resonates excessively, I add a 2x2 cross brace, shimmed and glued into place as Bill recommends.
It is possible to make 3/4" MDF boxes that almost seem like they are made out of concrete without too much work. Cross bracing is often skimped on in commercial products because adding it is labor intensive.
Semi OT anecdote:
Over a decade ago I built a 12" DVC subwoofer that seemed good enough for the purpose at the time. About 2 years I repurposed it as a subwoofer for a SR system and for the first time really put the driver through its paces. I upped the amplifier power from 400 watts to 2,000 watts. In actual use the amp often ran just below clipping or maybe even into a little clipping. The room went from 12' x 15' with a 9 foot ceiling to 120' x 45' with a 27 foot ceiling. Surprisingly enough the driver held together. However the enclosure experienced highly visible and audible flexing when driven hard. I added surprisingly small amounts of front-to-back bracing and tamed it back down. It ran at the edge of its performance limits weekly for almost 2 years.
One day I walked in and saw that it had been replaced, which was fine with me because it had been on the edge all along. I was never given any budgetary support for adding it or upgrading it so it was out of my hands. Nobody complained because I kept it just below its dynamic range limits. The system that replaced it had 2 18" drivers and was far larger. There was a funny story about how the bass player that had been detailed to replace it hooked up the new speaker with the same power amp and crossover settings and promptly just about blew the music director out of his office about 100 feet and several masonry walls away. It was about 12 dB more efficient and had good dynamic range reserves.
Eventually I decided to see what happened to the old subwoofer. Even though the bass player denied it under direct questioning, physical examination showed that it had ceased producing acoustical output. However, the problem was just an open connection in the internal wiring. The slings and arrows of trying to solder 12 gauge wire in the field with a 25 watt soldering iron. This time I came prepared with a 60 watt iron. It is still in service in a smaller room with a 400 watt amplifier and has plenty of dynamic range.