Knock, Swirl, Bloom and other contentious amp adjectives

G

grape

Experienced
So I would really like to understand some of the amp guitar terms. Let's start with Knock, Bloom, and Swirl. I'm wondering if we can come up with examples of each from the AxeFXII and the real amps.

Knock
Not sure how to define this. Cliff says he figured it out in the FW3 I think but I'm not sure what it is. I mean, I understand the description (sounds like you wacked the amp with a hammer) but I don't know what it sounds like in terms of playing through an amp.

Bloom
I think I can hear it best on some amps (bias, hardness, sag, proximity, speaker drive is what I played with to emphasize this). I will try to post an example of this. My understanding is that it sounds like a quick onset, shorter release compression when you lay into the strings (power chord). I think this guy's talking about it in this clip around 7:25 in reference to a trainwreck:
1959 Gibson Les Paul + Trainwreck Amp tech talk w/ Glen Kuykendall - YouTube

Swirl
I don't think people fully agree on this one... Some say it's chime, others say it's a phasey or shifting eq on sustained notes. I think the following clip demonstrates both in the first minute using a trainwreck amp:
1959 Les Paul & Trainwreck Amp - "Can You Hear It Ring?" - YouTube

Please add more references and descriptions :0)
 
The following is my (admittedly underinformed) opinion—


Knock

I'm not too familiar with the term "knock," but I do notice that the II has what I call a "live-amp snap" that I couldn't quite dial in on the ultra. The notes seem to jump out at you with an urgent immediacy. I wish I could describe this better, and I wish I knew what causes it (quicker response in the algorithms?).


Bloom

I've heard "bloom" used to describe two different things:
  1. A rapid increase in a note's volume immediately after it's been plucked;
  2. A gradual change in the harmonic content of a note as it decays.
I've heard definition 1 (or at least think I've heard it), but only at high volume. I'm not sure of the mechanism behind it; for all I know, it might be a psychoacoustic phenomenon—the ear's and brain's reaction to being assaulted by a sudden loud sound. Or it may be caused by a rapid sag in the power supply when the note begins, followed by a rapid recovery (this would require hitting the power amp hard). Or it may be something else entirely.

Definition 2 is caused by the amp coming out of saturation as the note decays. That causes the harmonic structure of the note to change. It's also influenced by acoustic feedback from speaker to guitar, which introduces resonances that are gradually unmasked as the distortion products decay.


Swirl

I think of "swirl" as bloom (definition 2 above).



This is all stuff I wish I knew more about. I'm looking forward to other folks' responses.
 
I'm not as knowledgeable about this but I had an amp for a short time that "swirled" for me. It was a Mesa Stiletto Ace (to bright for me so I got a Mark V instead,)... I would almost zero out on the presence and treble and boost the mids high, good amount of channel 2 gain and bass in the middle. Then I would also dial back the tone knob on my PRS Santana SE. I don't miss that amp except for that one sound which was this weird hazy psychedelic sound that swirled in it's harmonic structure. My Mark V will do it to with 6L6's on the lead channel but it isn't near as noticeable, more like a morphing of sustained high harmonics. The Stilleto though was as close to a swirl sound I have ever heard (with the above settings.)
 
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