Where does fatique come from?

I've heard systems in the past (also owned them ) that would fatique your ears after a certain amount of time. Always thought this was the speakers fault. Is this right? or a combination of Speakers, Receivers, Cd players, Etc. How much do you have to spend to get over the fatique factor, or is just personal to each person?
I personally feel the worst fatigue comes from a bad mid range followed by a harsh high end. Again I think speakers are the first consideration when trying to battle fatigue. Followed by the source then pre-amp/amp - receiver - int amp. It's actually a combination of all things from your room to power cables and interconnects. So again I think the best place to start battling fatigue is in the speakers. As far as how much - that's what ever you can afford to relieve the fatigue. An example my second set of speakers were the BIC formula 4's {$229 retail)(about 30 years ago). They were extremely bad in the mid's but had what I thought was great bass. Then I got the mission/cyrus 782's ($800 full retail 21 years ago). No they didnt have the bass of the formula 4's but the fatigue was gone. The mids and highs were a world better. Now I have the Dynaudio C1's {$7450 retail}(and demoing the C2's ($13,000 retail) as I type). The Mission/Cyrus never fatigued me so to speak but the Dyn's sound so much better to ME. Some people do not care for the Dyn's. Another example is my son has Klipsch kfl-30's. They have decent bass (although slightly muddy to me) but an IN YOUR FACE mid range which I can't take for much more than an hour. He loves them and I don't. So yes it an individual thing along with the equiptment and what you can afford. In home demo is my highest recommendation for any componets you may be thinking about.

An untreated room (no acoustical panels) can sound fatiguing, especially if your speakers are bright.

My recently treated listening room sounds great now, but before I could only listen at low volume for short periods of time.

Panels (ATS Acoustics, GIK etc) are inexpensive and make a huge difference.
Distortion is very fatiguing.
I believe it varies with the person involved.

Think about other situations that are fatiguing, such as driving at night in the rain. You have to concentrate at a very high level to correctly interpret what you see. The paint lines between lanes are hard to see, there is a lot of glare from oncoming headlights and visibility is just downright poor. Your brain can expend a lot of processing power to "correct" the information it is receiving. Most people feel absolutely drained after a long drive in those conditions.

Same thing with concentrating on a difficult test where a minor misreading of a test question could lead to a wrong answer.

Our brain has an amazing ability to sort through the information it receives (think of concentrating on one conversation in a noisy room), but that effort comes with a price tag attached. The harder it has to work the faster we feel worn down by the task at hand.

It is no different with listening to music. However, different people listen for different things. A particular overemphasis or deficiency may bother one person (and thus require more mental correction) more than it bothers another.

As an example, one listener may value midrange tonal accuracy more than good bass. Good bass with a inaccurate midrange will annoy that listener while another listener may be blase about a slightly off midrange yet strain mightily to supply the missing info to a bass line that is important to him. There are obviously a wide variety of parameters for each listener to prioritize in a fashion that is important to them.

That said, some errors are more likely to bug a high percentage of listeners. Edgy distortions probably top the list of near universal annoyances, but even then we all know people who are perfectly happy with their table radio with the blown speaker.
Usually from distortions occurring in the mid to upper frequency range.

One of the most common sources of fatiguing distortion comes from individual component's inability to accurately reproduce sharp transients and dynamics accurately. When these occur, the system cannot respond fast enough and fatiguing distortions occurs. Some may find sharp transients and extreme dynamics fatiguing as well even when accurately reproduced because these create the high pressure level variations in the air as sound is transmitted that can stress or fatigue the ear itself.

The problem is much more common with digital sources compared to analog/vinyl sources which is why I believe more find digital to be fatiguing than vinyl.

Planar and electrostatic speaker systems in particular ten to not move as much air and typically produce transients well and do not deliver in genreall deliver the extreme dynamics compared to conventional speakers using dynamic drivers. This makes them often an attractive option for those that may be fatigued by more dynamic designs.
Recordings can also be to blame. Some stuff on my system just makes me want to get up and turn it off, Sarah McLachlan, "Surfacing" comes to mind. I like her stuff, but this CD just sounds harsh. Then there is stuff I can just listen to for hours.
As covered by folks above, fatigue is mainly caused by brightness especially in the midrange to high frequency range. Sometimes there are simple solutions that can ameliorate on this "fault" other than swapping equipment or speakers. Two effective way out is in speaker placement and room treatments. Room treatments will greatly enhance the sound system while eliminating any deficiencies such as sharp piercing treble(which results in fatigue) or bass boom in the low frequencies etc. Also, you might be surprised that a simple speaker positionining may eliminate fatigue altogether by a minimum or no toe-in speaker placement.
Maggies are well known for being "easy on the ear". They are not fatiguing at all, sound better the longer you listen, and you are seldom inclined to stop as a result of fatigue. These are planar designs that have very good transient response (low distortion there) and they do not move a lot of air compared to conventional full range dynamic designs, so dynamics are generally not as fatiguing either.

Omnidirectional speakers, like OHM Walsh designs, can also be comparatively easier on the ears as well because they do not blast all the sound and the associated high pressure levels in the air directly at you. They tend to fill the room with music instead, more like what occurs at a live, un-amplified musical performance, which enables realistic listening levels with less fatigue as well.
Yes, direct sound to the listening position is certainly not too good. With the drivers directed away from the listening position especially the tweeters, the ears will not be subjected to direct sound that may cause fatigue. One may also be able to crank up the volume higher without hurting the ear-drums with some proper speaker placement especially with minimum toe-in. In this sense, I suppose that omni-directional speakers may hold an advantage although I have no experience with Ohm Walsh designs.
BTW, this is an excellent question. The best way to a pleasant listening experience is to eliminate or minimize factors that cause fatigue. It is something that is not discussed as often as are things like tubes versus SS, vinyl versus digital, detail, imaging, etc.
Long rambling posts ...
I am with Mapman and Ryder's rationale. Simply excessive energy in upper mids and lower highs in general. But it could be the entire midrange, if excessive. You would want as flat as possible in the mids and lower highs, then roll off is preferable in highs. Find a component in your system that is the culprit. It could be speakers, source or preamp or even cables. Look to the room in the end unless it obviously has overtly exposed reflective areas. In any case make your evaluation in near field listening to rule the room out. For now.
too many mistresses....
Reading all the spelling and grammer mistakes ( including my own ) here on Audiogon

Spelled "grammar".

Stop fatiguing yourself!
My experience is from the tweeters. I recently did a crossover rebuild to a vintage pair of speaker and used a high quality capacitor and resistors (Duelund). Also upgraded to a soft dome tweeter replacement and the fatigue were gone.

I can listen at normal levels for hours with pleasure.

Might explain why magnepans are easy on the ears-very clean and clear highs?
Shouldn't that be "all of the spelling and grammar mistakes" ?????
"Where does fatique come from?" - she sounds Turkish to me! :)
fatigue, in the neurological sense occurs after one reaches the adaptation level--sorry, you may need to go to the psychology books.

essentially, the rate of firing of neurons decreases to the extent that one's ability to differentiate is severely undermined.

using theaforementioned concept, a consistent and significant sonic signature of any nature, can induce "fatigue", after a period of time, which is listener dependent.

fatigue can occur, as has been suggested when one attempts to focus, i.e., listen critically and analyze, for some period of time.

could the word "fatigue", in the context of this thread, connote displeasure with the sound of a stereo system, rather than enervation ?

if so, any serious imbalance in frequency response can be annoying, even for a short time, without producing neurological fatigue, or a sense of physiologoical fatigue.
"fatigue can occur, as has been suggested when one attempts to focus, i.e., listen critically and analyze, for some period of time.

So there must be a lot of fatigued audiophiles out there according to this.

I thought listening to music was supposed to be relaxing?
listening to music can be relaxing if one listens for pleasure rather than to assess the sound quality of a recording or stereo system.

perhaps superficial listening is a way of avoiding fatigue. if your nerves aren't firing to much to begin with, you won't have to be concerned with a slow down.
Our ears use certain odd-ordered harmonics in order to determine loudness. We are very sensitive to these harmonics; if they are altered even by trace amounts we will develop 'listener fatigue' as it was know as in the old days.

Anything that can enhance these harmonics is a culprit: global loop feedback is a major sinner (which is why there are zero feedback amplifiers out there), non-linear devices such as transistors, transformers, cheap coupling capacitors, poor connections, breakup modes in loudspeaker drivers...

IMO a good system will not exhibit loudness artifact- no matter what volume level it is playing at, it will always be relaxed.
Fatigue might come from TIM distortions. In SS amplifiers with deep negative feedback output transistors go momentarily into saturation when feedback is too slow to respond to fast input signals (charge is trapped at semiconductor junction). These momentary gaps are not audible because our brains compensates by filling them. (causing fatigue).
You can find more about fatigue and TIM distortions in first paragraph here: http://www.valutronic.se/technique.html