ambisonics filtering 1 of 2

My goal is to find the best and effective method to isolate, in an Ambisonics recording (alone, done with only one first-order mike and no ancillary mikes of any type), the different instruments (or groups of instruments) being part of an ensemble or orchestra. This goal is, in my opinion, the main reason for recordists to use the Ambisonics recording method, so they can adjust the single levels of the various instruments in post and obtain a well balanced mix. I think this goal is primary for professional use, and this overcome in importance the spatiality 3D rendering, that is also important but only on a secondary plane. Obviously, when our goal is simply a 360 VR leisure filming, the 3D sound rendering jumps ahead at the first position, but here I want to talk and experiment in a more professional oriented field.

Here I have at my disposal two different Ambisonics VST plugins filters that can handle the directionality aspect of the soundfield: the “Rode SoundField” and the “Ambix Directional Loudness”, both freeware. I made some comparisons with these, but if you know about other plugins or methods to reach the main goal stated above about filtering single sources by directionality, let me know!

The parameters used in the SoundField plugin are clearly visible on the video, while in the Ambix Directional Loudness plugin I used all the 8 filters the plugin has, all in a passive -99 gain configuration. I placed four of them overlapping along the entire horizontal and vertical soundfield, roughly spanning horizonally from -90 to -135 degrees, passing from 0, and from -90 to +90 degrees vertically. This leaves a small vertical window from -135 to -90 horizontal degrees where the trumpet resides. Then I added two more filters above and two more filters below 0 degrees in this window, in order to isolate perfectly the trumpet instrument. The filters areas are marked by blue rectangles and a white circled number for identification in their geometrical center.

In the first video, we can hear the difference between the filterings done by the ambix directional loudness VST filter and the rode soundfield VST filter set as maximum shotgun mike configuration (the new acclaimed type of miking this pluging can sinthetize). To my ear, the directional loudness filter is clearly more effective to isolate the trumpet. You can see enabling and disabling the plugins by greening/de-greening their respective ON/OFF pushbuttons in the lower line of their respetctive windows or in the effects rack of the DAW. When enabling the the Ambix Directional Loudness, you can see on the SoundFiled Rode plugin radar the filtering effect: very noticeable!


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