Listener fatigue: what does it really mean?

Definitely agree with Atmasphere detail/brightness comments. Good or improved detail, upgrading a system component for example, to me is when you are able to hear things that were more hinted at but not defined before and relaxed presentation would also apply unless the recording calls for some thing different. Brightness definitely adds to fatigue. I guess what I am calling dynamics would be the ability for the system to reproduce accurately subtle as well as very energetic or loud musical passages. Accurately being the key phrase. This ability should make the music more interesting and less fatiguing IMO. I realize increased SPLs caused can cause amp clipping, speaker inablilty to reproduce, etc. and there must be a "noise" threshold for fatigue. Dynamic range might also be part of this discussion and seems strange to me. I think that a good analogy would be overly compressed mp3 files compared to HD FLAC files (well recorded and mixed ones). I say strange because 15ips reel to reel recordings do not have the dynamic range of say DSD, but there is something to them beyond their increased level of detail that makes them special. Maybe dynamics?

Learsfool,
Yes, you certainly understand the point I'm expressing. I totally agree that too often brightness is mistaken for detail. Many components that go the ultra detail and ultra resolution route sound false and artificial. They tend to sacrifice the actual full body and tone that's present when instruments are heard in a live setting.When you strip or thin out the tonality the resulting sound is less natural.
Dynamics are just as crucial at low/softer levels of music as they are at higher levels to communicate the music's emotion and full expression(similar to a voice inflection).

Learsfool, I have also personally reached the conclusion that lower power amplifiers with higher efficiency speakers produce a more natural and believable presentation.I can relate to you and your fellow musicians on that choice.
Regards,

I get fatigued with my music when I try to trim out my collection. I am not listening to it to enjoy it but to eliminate items. It must be done but I do not enjoy it hence fatigue. It lasts a while after so I find I do not listen intently for at least a few weeks after.

Charles1dad, to your point the problem we are having with semantics is that distortion often masquerades as dynamics. This is so common with audiophiles that I no longer use the term- I use impact instead, when referring to actual changes in dynamic contrast.

An excellent example in recorded from is side one band 2 of the Soria series (RCA) Verdi Requiem. Here you can experience the dynamic range from triple pianissimo (ppp) to triple forte (fff), IOW from very quiet to very loud, such that to play it properly will bring most systems to their knees in just a few seconds.

Now, with respect to the comment of lower powered amps on high efficiency speakers by Learsfool:

SETs have a particular distortion character that is exactly what I am talking about (although other systems can do similar things). In an SET, to really hear what the amp does you need to have a high efficiency speaker. This is because the distortion of the amp vanishes at lower power levels. When there is distortion it obscures detail. This is why SETs always get good marks for low level detail.

At power levels up to about 25%, the main distortion is the 2nd harmonic, followed in much lower amounts by the 3rd and 4th harmonics. These harmonics contribute to the lush character that SETs are known for. I have often thought that SETs have become more popular with digital products, as they seem to add harmonic structure that digital often seems to lack.

At power levels above 25-30%, the higher ordered harmonics come into play. SETs will typically have about 10% THD at full power. The higher orders contain in addition to more even-ordered harmonics, also the odd orders, the 5th, 7th and 9th (used by the brain to sort out how loud the sound is). Their presence is masked to our conscious hearing by the presence of even ordered harmonics, for example the 4th, which is louder than the 5th, masks the presence of the 5th.

However music is processed by the limbic system in the brain, and the presence of the odd ordered harmonics is not missed even though consciously we are not aware of distortion. Music has a lot of transients (dynamics) which demand greater power out of the amp. If you are playing the amp on a moderate to high efficiency speaker, depending on the power capabilities of the amp and the efficiency of the speaker, the power levels above that 25-30% level will only be showing up on the transients.

What this means is that the artificial loudness cues (odd ordered harmonics) will only show up on the transients. **This is why** SETs are often cited for having dynamics that seem far above what one should expect for such a low powered amp. We have all seen those comments in plenty of reviews.

The bottom line is what we are seeing in this example is distortion masquerading as dynamics.

SET amplifiers as a niche have finite limitations as do any other amplifier type, be it solid state, class D, OTL, push pull tube etc. Within a given amplifier category there's a hierarchy of quality and execution success. I find the limitations of SET or other lower power amps an acceptable tradeoff to get the superior sense of realism and naturalness they provide relative to other choices available (obviously YMMV)). There's compromise intrinsic to any and all amplifier topologies.Semantics, that's all it is. Call it impact or dynamics, the bottom line is this is a mandatory component of music.Without it, music is lifeless and unrealistic.
Regards,