Cone + Horn + Sphere
File: Cone - Horn + Sphere.axi
See also examples: Dome+Horn+Sphere
This example demonstrates an advanced setup and comparison to measurement.
Setup and Field-Plots
A 100mm cone is placed behind an aperture of 65mm, which forms a compression chamber. The sound exits the aperture into the conical horn of length 120mm and mouth-diameter of 235mm. In front of the horn is placed a rigid sphere of diameter 195mm. The distance between the bottom of the sphere and the horn-mouth is 100mm. Horn and sphere are identical to the experiment of a dome + horn + sphere.
The above field pressure contours are taken at approx 100, 1k, 2k and 5kHz. The SPL-range is 50dB for all plots.
Comparison with Measurements
The SPL measurements and simulations are taken at points on an arc of 300mm radius centered in the middle of the horn-mouth.
At low-frequencies the level drops because of the finite size of the baffle, which is approx. W = 950mm by H = 1150mm. The finite baffle also causes some diffraction-ripples in the range below 1kHz. The damping of the measurement chamber is fairly good above 500Hz. Below 500Hz reflections are to be expected.
The simulation appears 1dB or 2dB too loud, which most likely is caused by measuring the mass of the vibrating assembly too low.
Velocity Measurement of Diaphragm
The deviations at high frequencies are caused by eigen-vibration of the diaphragm, the dome and the surround. The above diagram displays the velocity at several positions on the cone (left) and dust-cap (right). These curves have been normalized to the response of the velocity at the connection point voice-coil - cone. The green curve is measured in the middle of the cone, the black near the outer surround and the purple curve stems from the center of the dust-cap.
With increasing surface-motion above 3kHz-4kHz also the sound pressure raises. Because AxiDriver models only the rigid-body mode of the diaphragm there are discrepancies to be expected.