The jump factor is one of the critical elements to fool us into suspending disbelief and getting into a state flow listening to music.
When it comes to speaker design, what is it about the "jump factor" that only very expensive speakers seem to get it right?
Not sure why you think the "jump factor" is right. And it certainly doesn't have to be an expensive speaker. It only needs to be a revealing speaker.
I would attest that the jump factor, though impressive and engaging to some extent, is nothing more than an electronics-induced distortion that actually takes you further away from the live performance rather than closer to it.
When is the last time you were at a live music performance (and seated at least 20 - 30 ft from the instruments) where you heard the strike of a note or a dynamic passage that caused you to jump?
Long ago, I've seen Ted Nugent, Al Stewart, KISS, ZZ Top, Rush, Bob Seger, James Taylor, Kenny Loggins, Freddie Hubbard, Dave Ramsey, and a small host of other artists. I've also been to a number of symphonies, jazz, and other concerts in large concert halls as well as in smaller more intimate venues. Never once do I recall experiencing the "jump factor".
Now I've been known to listen to certain types of music on my playback system around the 100 - 105db levels. Because of some unique things I employ, I also happen to possess the most dynamic playback system I've ever encountered and have taken great pride in my system's dynamics. It was not unusual to encounter the "jump factor" and it always seemed to be with the right dynamic note. A phenomena that is tremendously exciting and engaging and impressive to any visitor.
Nevertheless, it simply is not natural. There is a soundstage and there is an audience and usually a good distance between your ears and the artists and their instruments and/or speakers. That distance could be 50ft, 100ft, or even 200ft between you and the soundstage. Aside from an oil refinery explosion or maybe serious high-speed auto accident, there are very few sounds in life that occur 100ft away that would or should cause you to jump.
Think of it this way. If you have any experience with guns, then you know how powerful a gunshot is. If there was a .45 caliber gunshot that went off 5ft or 10ft away from you, you would jump every time you heard the gunshot.
But if the shooter was now say 50ft away, you most likely would never jump, though you may blink, whenever the gun was fired. At a 100ft. away, you probably wouldn't even blink.
So what exactly causes a playback system to generate a "jump factor"? Well, of course there has to be a certain loudness or higher decibel range because elevator or background music will never cause a jump factor. But more importantly, it is the distortions induced in a system that causes a jump factor. The very same distortions that make a piano, a percussive instrument, the most difficult instrument to reproduce, especially the upper registers.
The distortions induced in the playback system will cause a piano's upper register keys, especially when struck hard/quickly, distort a good portion of the note so that the most obvious part of the note, usually the most dynamic part, makes like a beeline to your ear. Better yet a laser beam to your ear, causing you to wince and causing ear fatigue.
So why am I confident about the Jump factor being the result of distortions?
Not long ago I took possession of a 600 wpc int. amp to replace my 200 int. amp. Until now the most powerful amp I've ever owned was a 300wpc@8ohm McCormack DNA-2 Revision A amp that also pumped out 1200 wpc@2ohms.
With my already impressive dynamics, with the 600wpc a note's initial attack was now so in-my-face (it almost didn't matter what the instrument was) that though very impressive, was so unnatural. It was as though my ears were now 6-inches from the instrument for the note's initial attack, but then my ears were planted in say the 1st row in the audience for the remainder of the note.
Even though the amp had tremendous promise from a musical perspective, this in-my-face situation was about as natural as a .45 caliber gunshot going off 10ft from my ears and it took the overall musical presentation in the opposite direction of live music. But I was jumpin'.
So I swapped out the 600 wpc int. amp with the same mtg'er's 600 wpc mono-block amps (same exact technology as the int. amp) hooked up directly to my CD player and used the CDP's passive volume attenuator.
It was a match made in heaven, as they say. The in-my-face dynamics from a note's initial attack was gone (for the most part) and back up on stage with the rest of the music and notes where they belong. And my ears were now planted well into the audience where they belong with a good 30 - 40ft distance between me and the soundstage just as it should be.
Switching to the CDP's passive volume attenuator brought additional benefits as well. A tremendous improvement in clarity where every note was that much more pristine and delicate so there was obviously a much lowered noise floor too. And because of the 600wpc amps, I still have the most dynamic system I've ever encountered, only now it is far more natural with a good natural distance between me and the soundstage.
Because of my love for dynamics, I swore long ago that I'd never switch to a passive preamp / volume attenuator but as a result, I'm now closer to the live performance than I've ever been and in a very natural sense of the word.
So what was the cause of my extreme jump factor? Several things.
1. There are things I do to my system that greatly reduces distortions (noise floor) while it improves its level of musicality, including dynamics. So there's already a "jumpstart" there.
2. A 200wpc amp wasn't enough to significantly amply the problem but I suspect the 600wpc amps greatly amplified a notes attack, especially for performances and instruments that were closely mic'd.
3. I suspect that most / all amplified gain stages induce a certain amount of distortion as most any amplifier will do.
4. I suspect with closely mic'ed dynamic music material a note's initial attack, say a kick drum or a blatt of a horn, moves or excites enough air to cause the recording mic's diaphragm to move and this movement or excursion (like a subwoofer driver) or PUFF of the diaphragm is captured in the recording. And when played back with an active or amplified gain stage and with 600wpc amps, this recorded PUFF at a note's initial attack is PUFF'ed out of the playback speakers.
Since a more revealing speaker (or component) is indiscriminate about what it reveals (music or distortions), it can be that certain speakers will amplify or make this unnatural distortion more distinct than a less revealing speaker. At mild levels the "jump factor" may be cool, but there simply is nothing natural about it.
Essentially, it took an extreme form of the electronics-induced "jump factor" and perhaps luck of the draw corrective action to realize the "jump factor's" potential cause and its cure.