Not sure where you have heard the recommendation for the cloud to be directly overhead. That is incorrect. Positioning it directly overhead will do nothing to mitigate the reflections with which you are concerned with respect to the listening position relative to the speakers. (Just what kind of spurious noises are you emitting???? :laugh: )
Remember that the angle of incidence equals the angle of reflection.
Simple ray tracing can help locate the cloud, while the use of the ETC response can absolutely insure its positioning to control the actual reflections as well as verify the effectiveness once installed and facilitate any adjustments necessary.
Note, while you did not mention the thickness of the panel, whether 2" or an optimal minimum of 4" (of optimal ~3lb/ft^3 Fiberglass or ~4 lb/ft^3 mineral wool), you will ideally want to suspend it with a minimum of a 4" gap from the ceiling for optimal broadband effectiveness for the specular energy. Note a 2" thickness will reduce the lower frequency extension effectiveness and allow those frequencies to still be reflected and impact imaging, localization, intelligibility and the coloration of the direct signal as the incomplete absorption will have the effect of acting as a high pass filter and effectively 'EQing' rather than eliminating the indirect energy.
The cloud is for the control of broadband (meaning above modal frequencies, hopefully extending low enough to incorporate the low-mid frequencies) specular reflections. Thin porous absorption placed near boundaries (in regions of low particle velocity) will have minimal effect on LF modal behavior. In fact, the aforementioned 'requirements' for an optimal minimum panel thickness of 4" with a 4" gap is required simply to extend the effectiveness down to the lower regions of the specular behavior - behavior that by definition begins after the modal behavior ends...
Remember that the angle of incidence equals the angle of reflection.
Simple ray tracing can help locate the cloud, while the use of the ETC response can absolutely insure its positioning to control the actual reflections as well as verify the effectiveness once installed and facilitate any adjustments necessary.
Note, while you did not mention the thickness of the panel, whether 2" or an optimal minimum of 4" (of optimal ~3lb/ft^3 Fiberglass or ~4 lb/ft^3 mineral wool), you will ideally want to suspend it with a minimum of a 4" gap from the ceiling for optimal broadband effectiveness for the specular energy. Note a 2" thickness will reduce the lower frequency extension effectiveness and allow those frequencies to still be reflected and impact imaging, localization, intelligibility and the coloration of the direct signal as the incomplete absorption will have the effect of acting as a high pass filter and effectively 'EQing' rather than eliminating the indirect energy.
The cloud is for the control of broadband (meaning above modal frequencies, hopefully extending low enough to incorporate the low-mid frequencies) specular reflections. Thin porous absorption placed near boundaries (in regions of low particle velocity) will have minimal effect on LF modal behavior. In fact, the aforementioned 'requirements' for an optimal minimum panel thickness of 4" with a 4" gap is required simply to extend the effectiveness down to the lower regions of the specular behavior - behavior that by definition begins after the modal behavior ends...
