25 drivers at once.
I show it as an example because I have it available. My speaker technically is a two way I guess, as I'm running subs nowadays that come in at 160 Hz. But... it has a linear phase crossover to not loose anything from that transient nature. It's what I wanted, its what I have.
What you are showing with the JBL is a tweeter, firing in front of a woofer, etc... The bandwidth of the tweeter will determine what the first part of the STEP looks like. This has
nothing to do with transient response or speed. It's just the tweeter's output that dominates the impulse/step.
If it had a linear phase crossover and hardly any reflections within the room, the STEP would stay flying above the center line for longer, and it could be called a good transient. But as is, it just isn't.
If it had a different type of crossover, it would look different too. Look up Dunlavy, check out his speakers and his STEP response.
Stereophile Dunlavy SC-IV
He had first order crossovers and used a single tweeter, 2 mids, 2 woofers in one big speaker. His speaker is fast.
(plucked this from the net, for information purpose only, for the original look here: link)
His STEP is longer above the center line than yours. This isn't done with DSP, just with common sense and engineering.
I cheat with DSP, why? Because it is available. John Dunlavy was working on a DSP model speaker and didn't get to finish it.
Look what he wrote about it in his paper, you can find it online. Read and learn. He knew his stuff....
An interview on Stereophile might help:
Interview John Dunlavy but his paper: Loudspeaker Accuracy holds way more information.