After quite some trial and error with various techniques to arrive at a genuine Ambisonic B Format reverb using Valhalla reverbs, I finally put something together that works.
This track template can be used in Ambisonic mixes to achieve genuine, three dimensional, B Format reverb with width, height and depth input and output. If you solo the reverb, you'll hear all your directional and panning cues in the reverb mix.
I've used a bunch of channel mixing techniques, M/S decode and encode and level correcting JS plugins (all stock REAPER plugins) in combination with three instances of (in this first template), Valhalla Vintage Verb. Every parameter for adjusting the reverb is linked so all that is necessary is to adjust the first instance of VVV and the other two will follow. This includes selecting presets too.
The track template uses 16 audio channels. Channels 1-4 are the B Format input and output, channels 5-8 are X (front/back) reverb, channels 9-12 are Y (left/right) reverb and channels 13-16 are Z (up/down) reverb. EDIT - Those channel arrangements are for the older FuMa format. Blue Ripple Sound have just released their new SN3D updates which have the channel arrangements as WYZX. This is directly compatible with YouTube 360 and Facebook VR. These track templates will work with both arrangements without modification
. Channels 5-16 are mixed internally in the track routing matrix and output back to 1-4. Those channels won't output to your mix so if you have other channels in the audio chain, it won't interfere with them. I am using this track template in third order Ambisonic mixes which have 16 channels of audio so I designed this template to work in that environment too.
Even though this template processes first order Ambisonics (channels WXYZ for FuMa or WYZX for SN3D), it is still very effective when used in higher order mixes. It isn't vital to have the reverb in higher order format to still be very effective.
All you need to do is send any B Format sends to channels 1-4 and the track will add reverb and output back to 1-4. If you are mixing in higher order Ambisonics, just send the first four channels to this track.
There's no reason you couldn't substitute any other stereo in/stereo out FX for the three instances of Valhalla Vintage Verb here to achieve genuine B Format FX. You'll need to set the channel i/o pins on each instance of your replacement FX the same way I have them set in the reverbs and you'll need to manually link each parameter from the second and third instance back to the first one if you want to have master control but it can be done reasonably easily.
I will be creating track templates for Valhalla Room, Valhalla Shimmer and Valhalla UberMod soon complete with parameter linking. I'm considering purchasing Valhalla Plate and if I do, I will include that too.
Download the Valhalla Vintage Verb Ambisonic track template here.
Download the Valhalla Room Ambisonic track template here.
Download the Valhalla Shimmer Ambisonic track template here.