What you're talking about seems to be something else than what I am talking about. It appears to me that you're talking about the standing waves that occur between boundaries (be they axial, tangential, or oblique). I am talking about the resonance that is inherent to a spring-mass(-damper) system. For a cavity this means that the air trapped in the cavity has a mass and a stiffness (and damping) which means it has a resonance frequency, just like a loudspeaker driver has a resonance frequency dependent upon its stiffness and mass. If the air is excited at this frequency, it will start oscillating/resonating heavily.
The more common term for a cavity resonance is "helmholtz resonance", which you may be familiar with. In the case of a ripole the helmholtz resonance of the slots is generally lower in frequency than the first standing waves in the slots, in other words increasing the frequency of the helmholtz resonance is a more efficient means of improving the ripole's bandwidth than making the walls non-parallel. Most helmholtz resonators are quite different in shape from the slots found in ripoles, but the basic principle is the same: a mass of air which oscillates strongly around a particular frequency.'
Let's say the largest dimension in a ripole slot is 34cm, in that case the first standing wave will occur at ~500Hz, which is already far beyond the frequency of the cavity/helmholtz resonance.
The more common term for a cavity resonance is "helmholtz resonance", which you may be familiar with. In the case of a ripole the helmholtz resonance of the slots is generally lower in frequency than the first standing waves in the slots, in other words increasing the frequency of the helmholtz resonance is a more efficient means of improving the ripole's bandwidth than making the walls non-parallel. Most helmholtz resonators are quite different in shape from the slots found in ripoles, but the basic principle is the same: a mass of air which oscillates strongly around a particular frequency.'
Let's say the largest dimension in a ripole slot is 34cm, in that case the first standing wave will occur at ~500Hz, which is already far beyond the frequency of the cavity/helmholtz resonance.
