What is the sound difference with the new build process?
I don't know if there are any significant audible differences. But we are always looking to continually improve our products.
The 3" port is a good example. A single 3" port has more total area than two 2" ports. This provides for greater air flow. Plus the flared openings create less turbulence than a straight port. The only drawback is that the 3" port has to be longer to arrive at the same cabinet tuning.
We started using this port on the SongTowers and wondered if it would work for the HT3's. We thought that perhaps it would require too much length for the design. But when we did the calculations, we found that it would work.
At the same time, we were developing templates to use the same production system for the HT3's that we now use on the SongTowers. So in cutting the templates, we had to decide which direction to go and opted for the new port.
Does it make a difference? From a theoretical point of view, yes. Less port noise should be the result. As a practical matter, I doubt you could hear the difference. First, the port noise from two 2" ports was quite low to begin with. Second, the port exits out the rear of the cabinet and the sound emanating from the woofer masks any port noise that might be present.
As for the build process, there is now no possibility of telegraphing seams since all joints are mitered. Plus there is 50% more glue suface in a mitered joint, so it is stronger. Dadoing the braces in place also increases their glue surfaces and locks them in place. It all makes for a more rigid cabinet. Does it sound different? Probably not. But it is better, so we made the change.
We chose to make these changes because small incremental improvements add up over time and our aim is to continually improve our products. We normally don't even talk about changes like this since we make them on a constant basis.