Nearly 90 degrees off the speaker's axis in an AR3/AR3a, there is a reflector around the perimeter which in aggregate is approximately 1 square foot in area (4 foot perimeter and no more than about 3" wide) and is evenly distributed. It reflects at what appears to be about a 30 degree angle. Are you saying this reflector adds 10 db to the speaker's output at any frequency compared to the drivers without this reflector? I find that hard to believe. Certainly the tweeter's output 90 degrees off axis is relatively small compared to its forward output. To the degree that these reflections exist, they will create multiple comb filtering, so many because each point along the reflector is another source that the interval of frequency nodes and number of nodes at any given point in space are so numerous that will tend to cancel each other out. At least that is the theory. That is why I asked for any reference to measured data. It strikes me that like many audiophile notions, this type of generalization is not only theoretically flawed, it is not proven out by experience. This is typical for the arguments for wires, vacuum tubes, vinyl phonograph records, and many other audiophile notions that run contrary to factual knowledge. In fact audiophile notions generally fly directly in the face of real scientific knowledge and the experience of engineers even if the audiophiles have gone into the manufacturing business and have products to sell.
You need to read what I said again. I was refering to Olson's study and his measurements of a small driver on the face of a variety of cabinets. Worst combinations, with the unit in the center of a highly symmetical cabinet, gave 10dB peak to trough. More typical cases gave 2-3dB. These are diffraction related edge reflections alone. Perimeter dams would be a seperate additional issue. I'm not sure I would lump these in with cables and vacuum tubes. Olson didn't strike me as a tweak..
Which is why the oboes are at the front of the Orchestra....oops. Yes, musicians need to play in reverberent space. That doesn't mean that similar reflections are good for the accurate reproduction of sound. I like the studies of Soren Bech where he showed that the floor bounce is the most likely, after the back corner reflections, to be audible, i.e.detrimental.
Reflections off the floor are critical to the sound of many musical instruments. For example, many wind instruments like clarinets and oboes direct their sound almost exclusively at the floor. The way in which the performing stage is constructed can directly affect the bass response of an auditorium as it is a critical reflector of large area near the sources of sound. Cancellations due to the Allison effect can easily be equalized out.
One Allison like effect is the odd absorption characteristic of the audience to grazing waves across. I'm sure you have read about that. Within the orchestra shell don't you have a large quantity of sources all at varied distances from the closest boundary? Hard to see how that would give any uniform cancelation.
Depends on what you mean by "greater concern" we were talking about reflection related response aberations. The general directivity rise of speakers with frequency is another debate. If you want to see and hear the effects of edge reflections then they are most likely to be visible at mid and high frequencies. Distance of the driver to the edge determines the delay time for alternate paths and hence the wavelengths of cancelation or addition. Low frequency wavelengths are too long, the waves diffract but the reflections don't cause cancelation.
Diffraction around the back and sides of cabinets is of far greater concern at low frequencies than at high frequencies. This is only one reason why a forward firing speaker will sound muffled from behind. Only the lower frequencies radiate omnidirectionally to the sides, top, bottom and back of the cabinet and create reflections within the room that drastically alter the tonal balance of the speaker. This is why there is little correlation between the on axis anechoic FR and the real room FR when all of the sound reaching the listener including the reflections are collected. Moving the speakers away from the walls and adding sound absorbing material only marginally mitigates the problem.
"We tend to be a little sloppy with our terminology."
I've noticed. It hardly stops there though.