Transient responses from a speaker is a very curious topic. I always interpret what transient means by comparing the Appalachian mountains to the Rocky Mountains. Attack of an instrument being relayed through a recording, level of crispness in what you’re listening to, and what the hell goes on during a recording session when they’re playing with all these levers.
I always liked JBL speakers, have not heard them for a while.
I think what’s really important here is the quality of the amplifier and how it handles that sort of thing in relation to whatever the speaker achieves.
Probably tough to get a good definitive answer here. Sealed speakers are not that common and there's plenty of portage speakers that probably give really good transient response I'm not sure there's a distinction between the two.