I can see the tube connectors on more inexpensive stuff that people DIY. You do have to reterminate your speaker wire with the tube male connector.......not such a big deal for those who are DIYers and make their own cables. But people buying $20,000 speakers? Most of these people already own speaker wires that are expensive and probably terminated with spades. How are they going to use their speaker cables? They cannot.
The tube connectors are not sonically better than the binding post bypass system. The binding post bypass system allows you to use any spade or bare wire speaker wire and clamp it directly to the wire coming out of the speaker. The only limitation of the binding post bypass system is you cannot use really large gauge wires coming out of the speaker to wrap around the outside of the binding post for the clamp. The binding post bypass system can be used on amps too....same results....you cannot go back to any binding post.
However, a plastic or wooden clamping system is even more transparent. Even the mass of the connector messes up the sound even though you are clamping the wires together......so the best thing is clamping without any metal. A clamp system also allows the customer to also use Zobels, Ground Enhancers, Bybees, whatever, in conjunction with the speaker wires.
The picture below shows a cotton covered wire coming out of the amp through some grommets using very inexpensive binding posts. This could be made to look mucho better for the serious money people.
