Originally Posted by Ricci
It appears that there is either severe compression occuring in the drivers or that there is some sort of acoustic limiting or compression occuring inside the horn itself. i am leaning towards some of the later. Thoughts?
It seems that horns, even bass-horns, are subject to nonlinearities due to the nonlinear nature of air.
This nonlinearity can cause nonlinear distortion (harmonic distortion).
In you case here, it may seem that it can also affect the frequency response of the system, in a non-linear way.
I found some odd behaviour during testing with acoustical damping, and in that case the distortion level was highly influenced by the amount of damping.
Type of damping did not show significant differences.
Since the design was a success, part from some distortion in a narrow frequency band, I did not pursue this any further.
Now, what is actually causing this, I do not know.
Maybe we can find out.
It may also be mechanisms of different origin, causing the same kind of measurable artifacts.
Changes in driver parameters as the power is increased could be worth investigating.
This may be worth some more investigation, seeing as it would be nice to be able to simulate or at least calculate the distortion level earlier in the design phase.
Also, it will be possible to reduce the distortion by making better designs, if one knows what causes it.