When you say TB-15 hub, are you referring to the TB15 dock? If so, fyi Dell recalled all of those a long time ago due to significant and widespread hardware issues, and replaced them with the TB16 dock. If that's what you already have, then the TB16 already has an "upstream" Thunderbolt connector, so you could connect the dock directly to the system and connect the display to the upstream Thunderbolt port on the TB16. However, I'm admittedly not sure that the Thunderbolt 2 adapter needed for the Apple Thunderbolt display would work that way; I haven't read anything either way.
Also note that even if you found a Thunderbolt 3 "hub", connecting the dock to your system through a hub will probably prevent the dock from charging your system properly, or at all. The XPS 15 9550 requires 130W to function properly. The official USB-C/TB3 spec only supports up to 100W, but Dell has done something proprietary to allow the TB16 to provide 130W when the TB16 itself is powered by a 240W adapter. Chances are that won't work through a hub, in fact you might find that the hub only supports a lower power delivery rating (such as 60W) or none at all. So if you need more than the additional upstream Thunderbolt port already available on the TB16 dock, you should plug the hub into that port on the dock and keep the dock connected directly to the system, rather than placing this hub between the dock and the system. That said, the only Thunderbolt peripherals I've ever seen that offer upstream Thunderbolt ports are Thunderbolt docks; I don't know of any "hubs". And the only Thunderbolt dock that will properly charge an XPS 15 9550 as of this writing is the TB16, because again the XPS requires Dell's proprietary 130W charging strategy, and the TB16 is the only Dell Thunderbolt dock that connects to that system.
jphughan
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14K Posts
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March 7th, 2019 08:00
When you say TB-15 hub, are you referring to the TB15 dock? If so, fyi Dell recalled all of those a long time ago due to significant and widespread hardware issues, and replaced them with the TB16 dock. If that's what you already have, then the TB16 already has an "upstream" Thunderbolt connector, so you could connect the dock directly to the system and connect the display to the upstream Thunderbolt port on the TB16. However, I'm admittedly not sure that the Thunderbolt 2 adapter needed for the Apple Thunderbolt display would work that way; I haven't read anything either way.
Also note that even if you found a Thunderbolt 3 "hub", connecting the dock to your system through a hub will probably prevent the dock from charging your system properly, or at all. The XPS 15 9550 requires 130W to function properly. The official USB-C/TB3 spec only supports up to 100W, but Dell has done something proprietary to allow the TB16 to provide 130W when the TB16 itself is powered by a 240W adapter. Chances are that won't work through a hub, in fact you might find that the hub only supports a lower power delivery rating (such as 60W) or none at all. So if you need more than the additional upstream Thunderbolt port already available on the TB16 dock, you should plug the hub into that port on the dock and keep the dock connected directly to the system, rather than placing this hub between the dock and the system. That said, the only Thunderbolt peripherals I've ever seen that offer upstream Thunderbolt ports are Thunderbolt docks; I don't know of any "hubs". And the only Thunderbolt dock that will properly charge an XPS 15 9550 as of this writing is the TB16, because again the XPS requires Dell's proprietary 130W charging strategy, and the TB16 is the only Dell Thunderbolt dock that connects to that system.