Philb7777,
As for the bearing. My Raven AC was one of the earlier units. The bearing was convex on top. Similar to the BN. So is my BN. I think the diameter might be different. Both Dead quiet. Maybe 10 years ago there was a different type of bearing. But as the Phantom had a 1,2 Supreme and upgrades within the designation of each TW has done upgrades as parts have changed availability. This is the same in any industry. I also know that as items are in the market over time feedback will lead to design changes and upgrades. Also manufacturing will evolve as demand changes. A good company will work as such.
As for the bearing. My Raven AC was one of the earlier units. The bearing was convex on top. Similar to the BN. So is my BN. I think the diameter might be different. Both Dead quiet. Maybe 10 years ago there was a different type of bearing. But as the Phantom had a 1,2 Supreme and upgrades within the designation of each TW has done upgrades as parts have changed availability. This is the same in any industry. I also know that as items are in the market over time feedback will lead to design changes and upgrades. Also manufacturing will evolve as demand changes. A good company will work as such.