Isn’t it interesting that bass slam and quality comes not from woofers but instead from above?
Here’s what I mean by that. If you take a 3-way system like the IRSV, where the middle frequency drivers reproduce frequencies down to 100Hz, what you find is that bass impact and speed is determined not by the woofer towers, but rather the midrange drivers. Which is why we can accurately evaluate the bass performance of a power amplifier without that amplifier powering the woofers.
This applies not just to big systems like the IRSV. Just about any 3 or 4-way system will work the same way. Listen only to the woofers while music is playing and what you hear on a plucked bass note is little more than a dull thud. There’s no slam or impact to that sloppy thud because the frequencies that give the feeling of speed are much higher than the lower notes.
You can also listen just to the output of a subwoofer and get the same result: whoomp, whoomp, thud, thud.
It’s the upper ranges of bass that give us the impression of a fast woofer.