I guess my post was confusing.
I didn't mean that Everest said room modes or modal prediction or obliques were irrelivent.
As DJ said, Everest wrote "that tangential modes have only 1/2 the energy of of axials, and obliques only 1/4."
And Jeff said that they could be more powerful or less or equal or whatever. Leo Beranek has an example where the tangentals and obliques are stronger than the axials.
My position is that it doesn't matter who's right. What is irrelevent is which is the stronger mode group: axial, tangential, oblique.
Because for example if you believe Everest and have a strong axial and a weak tangential that are within 1hz of each other, they're going to add to make something stronger than the axial alone (at some spots in the room?). So the fact that the tangental exists is still important, even if at half the strength. So it's important to know the frequency of all modes. A post-build measured resulting mode's strength will be determined by other things.
So when I say 'irrelivent' I mean it's irrelevant which mode group is strongest. (whether one is stronger or not is another argument which I'm not qualified to give an opinion on other than quoting others, but for the purposes of predicting the frequencies which is strongest is irrelivent)
Everest's actual quotes are, from page 333 of 4th of "Master handbook of acoustics"
Presumably he's talking about reasonably reflective surfaces like drywall/gypsum.All modes do not decay at the same rate. Mode decay depends, among other things, on the way absorbing material is distributed in the room. Carpet on the floor of the test room has no effect on the 1,0,0 or 0,1,0 axial modes involving only walls. Tangential and oblique modes, which involve more surfaces, would be expected to die away faster than axial modes that involve only two surfaces. On the other hand absorbtion is greater for the axial modes in which the sound impinges on the surfaces at right angles than for low angle of incidence common for tangential and oblique modes
and from page 350
Tangentail modes have only half the energy of axial modes, yet their effect on room acoustics can be significant... oblique modes, having only one-fourth the energy of axial modes, are less prominent than the other two.
In other words, from what you wrote
Yes. Just lower in some cases.I don't think Everest says it is irrelevent, just lower in most cases.
Yes, me too.I agree with Jeff at some point you will run into a strange room.
Yes.How close the modes are and if they are "stacking" is the more important part.