Horn profiles
Conical horn
Straight walls from throat, mouth and wall angle. See how slowly a cone loads the driver compared with a curved flare.
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Horn profiles
Straight walls from throat, mouth and wall angle. See how slowly a cone loads the driver compared with a curved flare.
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Normalised to ρc/St. Solid traces: this horn, cut into conical elements and terminated by a baffled-piston mouth. Ripple is the mouth reflecting part of the wave back to the throat.
| # | x (mm) | ⌀ round (mm) | □ side (mm) | area (cm²) |
|---|---|---|---|---|
| 0 | 0 | 50.00 | 44.31 | 19.63 |
| 1 | 39.69 | 95.83 | 84.93 | 72.13 |
| 2 | 79.39 | 141.7 | 125.5 | 157.6 |
| 3 | 119.1 | 187.5 | 166.2 | 276.1 |
| 4 | 158.8 | 233.3 | 206.8 | 427.6 |
| 5 | 198.5 | 279.2 | 247.4 | 612.1 |
| 6 | 238.2 | 325.0 | 288.0 | 829.6 |
| 7 | 277.8 | 370.8 | 328.6 | 1080 |
| 8 | 317.5 | 416.7 | 369.3 | 1364 |
| 9 | 357.2 | 462.5 | 409.9 | 1680 |
| 10 | 396.9 | 508.3 | 450.5 | 2029 |
| 11 | 436.6 | 554.2 | 491.1 | 2412 |
| 12 | 476.3 | 600.0 | 531.7 | 2827 |
The conical horn is the simplest flare: straight walls that meet at a virtual apex a distance behind the throat. With half-angle ,
A wave in a cone is a section of a spherical wave, and the throat impedance of the infinite cone follows directly:
There is no sharp cut-off. Resistance and reactance are equal at , and the resistance only reaches 90 % of at . A wide cone on a small throat therefore loads the driver poorly at low frequencies compared with an exponential horn of the same length, as the dashed curve in Fig. 2 shows.
Straight walls do not bend the wave-front, so a cone radiates into a nearly constant angle set by its walls from the frequency where the mouth is a wavelength or so across. That is the basis of every constant-directivity horn. Combine this sheet with the constant-directivity mouth calculator to size the mouth for the lowest frequency of pattern control.