I friend came over and was listening to the swifty's I built and suggested that I cover the inside of the cabinets with Dynamat, the stuff car audio installers use to kill vibration and road noise to make them sound better.
is this true or false? Why would I want to do that?
If the box is resonant , using thin mdf or inadiquate brace, It would certainly benefit form using dynamat.
But if the box is well made using thick mdf for it's size with good bracing, I dont see any benefits from using dynamt , unless the dynamat is at least 10mm thick, which would result in reduction of the box volume and pain in the wallet.
In any case, I suggest, you build the box solid and non resonant in the first place.