DIY Internal bracing for NHT 2.9

I have a pair of NHT 2.9's and the cabinets produce a fair amount of vibration when played at enthusiatic levels. I have thought about removing the side mounted woofers to access the inside of the cabinet and placing 1"fiberglass rods cut to the width of the cabinet and epoxying them in place to stiffen the cabinet. The question I have is whether or not the solid (and very stiff) fiberglass rods are the correct materials to use, or if there is another material that would be better suited. Or is this even a good idea to begin with?
It sounds like a mistake to mean. The drivers were voiced with the cabinet as designed. I suspect you will be unhappy with the results.
Don't do it. Narrod is right, as you'll simply be shifting the resonance to a higher frequency. If the resonance is too offensive, sell them.
Personally, I know just what you mean about the bothersome resonance.

A close friend of mine who is probably the most respected loudspeaker modder in the industry almost ALWAYS makes addressing this issue a prime focus of his efforts. He uses Dynamat (whatever the best one is these days) on the inside of the cabinets. However, he cautions to not use TOO much, as you don't want to remove the soul of the music. The Dynamat will give you superior dampening to the fiberglass rods.

Needless to say, he's a very creative and talented person. One who eschews the conventional wisdom in favor of what he has found to produce the best sonics.
You also may want to look into Black Hole 5 or No Rez products. I used Black Hole 5 very successfully to accomplish what you want to do. The good thing is you just add what you need.

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