Clio09, the listening fatigue thing goes back to how the ear/brain system processes sound.
When a sound first reaches the ears, a copy of it is stored in a short-term memory. Then for the next twenty milliseconds or so, all other incoming sounds are compared with the sound(s) in our short-term memory, to see if they are NEW sounds or REFLECTIONS, that is, repetitions of the original signal. If they are reflections, then they're largely ignored as far as directional cues go. This is called the "precedence effect" or "Haas effect", after the researcher who first reliably described it. During this interval, reflections still contribute to loudness and perceived timbre.
Now the way the ear/brain system determines whether an incoming sound is a new sound or a reflection is by "looking" at its spectrum. If the spectrum is the same (or close to) that of a sound that's in the short-term memory, then it's a reflection. If it's obvoiusly different, then it's a new sound.
So, what about a reflection that's quite a bit different from the original? Well that hasn't been thoroughly investigated yet, but I believe we would find a continuum along which a spectrally-different reflection goes from "easy for the ear/brain system to correctly classify as a reflection" to "too distorted to be reliably classified". And I think that as the spectrum of the reflection differs more and more from that of the first-arrival sound, the more processing the ear/brain system has to do to correctly classify the reflection. In computer terms, it's like a task that uses up a lot of CPU power... and so the CPU heats up (we get a head-ache, after about 15 or 20 minutes): Listening fatigue. This isn't its only cause, but I believe it is a fairly common one.
Now remember that during the time the ear/brain system is ignoring directional cues from reflections, they are still contributing to loudness and perceived timbre. So a speaker may measure "flat" on-axis, but not sound "flat" because of the timbre-skewing contribution of the reverberant energy.
* * * *
Roscoeiii, I don't know the inner workings (including the impedance curve) of enough other manufacturers' speakers to give a really good answer to your question. Coincident comes to mind, and I think that KCS and PiSpeakers and Omega Loudspeakers and Tonian Labs are likewise strong candidates. Yours truly uses a variable-length port system so the box tuning can be adjusted for different amplifier damping factors (and different low-frequency acoustic environments).
When a sound first reaches the ears, a copy of it is stored in a short-term memory. Then for the next twenty milliseconds or so, all other incoming sounds are compared with the sound(s) in our short-term memory, to see if they are NEW sounds or REFLECTIONS, that is, repetitions of the original signal. If they are reflections, then they're largely ignored as far as directional cues go. This is called the "precedence effect" or "Haas effect", after the researcher who first reliably described it. During this interval, reflections still contribute to loudness and perceived timbre.
Now the way the ear/brain system determines whether an incoming sound is a new sound or a reflection is by "looking" at its spectrum. If the spectrum is the same (or close to) that of a sound that's in the short-term memory, then it's a reflection. If it's obvoiusly different, then it's a new sound.
So, what about a reflection that's quite a bit different from the original? Well that hasn't been thoroughly investigated yet, but I believe we would find a continuum along which a spectrally-different reflection goes from "easy for the ear/brain system to correctly classify as a reflection" to "too distorted to be reliably classified". And I think that as the spectrum of the reflection differs more and more from that of the first-arrival sound, the more processing the ear/brain system has to do to correctly classify the reflection. In computer terms, it's like a task that uses up a lot of CPU power... and so the CPU heats up (we get a head-ache, after about 15 or 20 minutes): Listening fatigue. This isn't its only cause, but I believe it is a fairly common one.
Now remember that during the time the ear/brain system is ignoring directional cues from reflections, they are still contributing to loudness and perceived timbre. So a speaker may measure "flat" on-axis, but not sound "flat" because of the timbre-skewing contribution of the reverberant energy.
* * * *
Roscoeiii, I don't know the inner workings (including the impedance curve) of enough other manufacturers' speakers to give a really good answer to your question. Coincident comes to mind, and I think that KCS and PiSpeakers and Omega Loudspeakers and Tonian Labs are likewise strong candidates. Yours truly uses a variable-length port system so the box tuning can be adjusted for different amplifier damping factors (and different low-frequency acoustic environments).