Relationship of flare frequency to resonance frequency ?

This is the very beginning of my first attempt to design a horn enclosure.
I was attempting use this driver www.pyleaudio.com/manuals/PDW21250.pdf and this mathmatical model www.rocketsciencecanada.com/rocketscienc...orns/Info_Design.asp .
After the first calculation (throat area) it was evident the writing was on the wall.This combimation would yeild a horn too big to go through the doors of most clubs in my city. I decided to do the math anyway believing I might learn from it.
As i began calculating Mouth area I ran into a variable I did't know off how to get,cut off frequency or flare frequency. I started to use the resonance frequency,but I don't think that can be correct. If the flare frequency is where the horn starts to unload then shouldn't that be set to specific preportion BELOW the resonce frequency?
I have experienced a horn be driven beflow its abilty to load, and its not exactly one of my favorite experiences!
Is ther a specific formula for cut off frequency relative to resonance frequency?

If you are refering to the driver's free air resonant frequency (fs), I don't think this really comes into it as this will change according to your rear chamber volume. I read somewhere that it is better to have the resonant frequency significantly higher than the horn cutoff. I usually choose the flare frequency to be the lowest frequency I want to produce (for a bass horn, this would be impractical for a mid horn.)

kieran wrote: If you are refering to the driver's free air resonant frequency (fs),

Yes I am !

kieran wrote: I don't think this really comes into it as this will change according to your rear chamber volume.

Interesting point !

kieran wrote: I read somewhere that it is better to have the resonant frequency significantly higher than the horn cutoff.

Thats what I was getting at ! Is there a good rule of thumb ?

Anyway,thanks for the reply. Its all food for thought !