By bloom do you mean harmonics. Atmosphere, I think I found the
corresponding website ;-) how would something would sound with loss of
“low-level detail” which is what happens with push pull amps. I’m
guessing more “bandwidth” is more frequency response or range?
Do SET,s lose their”bandwidth” or fail only when pushed to hard/loud?
@recluse 'Bloom' is an audiophile term that often refers to 2nd harmonic distortion. Often but not always.
A loss of low level detail will take some of the life out of the 3D soundstage as room ambiance is often part of low level detail. IOW quieter sounds that are part of music.
'Bandwidth' is akin to frequency response. This can be important to getting things like the soundstage correct, as phase shift can occur as an artifact to 10th the cutoff frequency (so if its good to 20KHz, down to 2KHz) and to 10X the low end cutoff (so if good to 20Hz, up to 200Hz). Phase shift messes with instrument timbre and soundstage width and depth.
For this reason, 2Hz to 200KHz is required to really get the soundstage right, and to assure impact in the bass.
SETs have troubles making bandwidth on account of their output transformers; its a real trick to make an output transformer that allows for power and bandwidth at the same time; 7 watts is about the practical limit. It is for this reason that the smaller SETs are also the best sounding. This really limits the speakers you can use, since one of the best sounding platforms for SETs is the type 45 triode power tube, which is good for about 0.75 watts at full power. There is a bit of a diminishing return here, as a speaker that is usable with that kind of power won't be able to play any bass anyway. But these days people often supplement the bass with a powered subwoofer.
When pushed hard, SETs don't loose bandwidth, but they do make considerably higher distortion. As a general rule of thumb, to really get your amplifier investment dollar out of an SET, the speakers used should allow you all the volume you need while the amp never goes above about 20% of full power. If you follow this rule, the amp will not make appreciable distortion. If you break it, you will experience the 'way more dynamic than it has any right to be for that kind of power' that you hear many audiophiles and reviewers describe about almost any SET.
(I may have ruined it for you by letting you in on this fact, as you may now be aware that some of the 'dynamics' you hear from SETs is really just distortion.)
The reason this happens is because the higher ordered harmonics (5th and above) start to show up about about 20-25% of full power. The human ear uses these harmonics to sense sound pressure, so if the amp is making them, it will sound louder. This is why many people have loudspeakers that are not efficient enough for the amp, but claim that its 'loud enough' for them- the harmonics are convincing them that its loud. A sound pressure meter reveals the truth of the matter!
The thing is, if you really want to experience high end audio properly, the system should **not sound loud** at any volume (and this is quite possible with SETs with careful speaker selection)! You should find yourself yelling at someone else in the room to be heard as a first indication that the volume is up. The reason this is possible is because if you use tubes, you can build a system that is free of the higher ordered harmonics.
