Web Audio API: Layout to Achieve Panning for an Arbitrary Number of Sources

I am trying to achieve user-controlled panning for any number of simultaneous web audio sources. The sources themselves are mono. I'm working in Javascript with the web audio API (https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API).

Currently, the problem I'm running into is that I'm trying to use a multi-channel output (one for each source), but the channel interpretation is overriding my attempts at panning (see https://developer.mozilla.org/en-US/docs/Web/API/AudioNode/channelInterpretation), leading me to think I'm doing something wrong architecturally.

I'd like to leave things at a mostly conceptual level here, since I believe that's where my problem lies.

Current Setup

My approach to this involves having one node handle all the processing for every source, called 'scriptNode' here. A number of channels equal to the number of audio sources is created, and a similarly equal number of panner nodes are created as well. The graph looks like this:

The bundle size (the '=' segments) is the number of channels, set to be equal to the number of sources.

scriptNode == splitter =+-- panner1 --+= merger == destination
                        \-- panner. --/
                        \-- panner. --/
                        \-- pannerN --/

Some miscellania, I'm calling this function to set scriptNode up:

scriptNode = firstPart.audioCtx.createScriptProcessor(2048, 0, numParts);

Where numParts is the number of sources. I'm also setting scriptNode's channelCountMode to 'explicit' and channelInterpretation to 'speakers'. One of these settings may end up being important, but I couldn't find out anything when trying to fiddle with the settings.

The Problem

When I actually test my code with this architecture, I will get the following behavior based on the number of parts I choose. The panning sliders are tied to the panner node's "pan" values for each respective source.

• numParts=1 : Mono output, panning with a slider doesn't do anything but affect the volume of the output (stronger toward the middle). I imagine this is a byproduct of downmixing to mono from a panner.
• numParts=2 : Stereo output, one hard left, one hard right. Panning both channels with a slider doesn't do anything.
• numParts=3 : Same as =2, but third channel is silent.
• numParts=4 : Similar to =2, now all channels work again, they are panned hard in an L/R/L/R order. Panning with a slider again doesn't do anything.

This behavior seems to fall in line with the channelInterpretation description, but what I want is to have panning work for each source separately, regardless of the number of channels I use. And I'd still like to use channels because each of my sources expect to write to a mono buffer.

Is there an architectural tweak I can make to keep this multi-channel strategy and achieve what I'm looking for?