Rear Wall Reflection Simulator
Version: 1.02 (2019-08-23)
Software platforms: Excel | OpenOffice | LibreOffice
Reflection from the wall behind the speaker is a common problem in small rooms. The reflected sound waves from the rear wall interfere with the direct wave and the result is a series of notches in the response curve below the center frequency of the baffle step.
This simulator calculates the front (on-axis) and rear radiation from a speaker baffle. The type of the simulated loudspeaker is 'boxed speaker' and the reflection from the rear wall is 100% (no absorption and diffusion, e.g. brick wall without acoustic treatment).
At low frequencies where the wavelength is larger than the dimensions of the baffle the speaker radiates evenly in every direction (spherical radiation pattern). At high frequencies where the wavelength is shorter than the baffle dimensions the speaker radiates only in the front half space, and there is no rear radiation (hemispherical radiation pattern). The transition between the two regions is the "baffle step": a 6 dB loss in front of the speaker at low frequencies in free field.
Due to baffle diffraction and other wave propagation reasons, as the frequency increases the spherical radiation gradually turns into hemispherical. The high frequency content of the radiated sound in the rear space is attenuated ("low-pass filtered") by the cabinet. What is very important that both the baffle step and the rear radiation are functions of the baffle dimensions.
Format: xls (Microsoft Excel 2003 Workbook)
Required software: LibreOffice Calc | Microsoft Excel | OpenOffice Calc
License: freeware
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Changes in version 1.02.:
- Improved baffle step and rear response (better agreement with measurements when the speaker is close to the rear wall).
More about baffle diffraction & baffle step (external links):
'The Edge' baffle diffraction simulator and baffle designer by Tolvan
Baffle Step Compensation by Rod Elliott (ESP)
Loudspeaker Diffraction Loss and Compensation by John L. Murphy (True Audio)
Similar software & related article:
Room Boundary Simulator
Frequency response of a speaker cabinet on the rear axis
