Studio Mystery!

Hello, all -

Studio mystery: Unable to get sound through one path on right channel in studio. Any help solving this would be much appreciated by the expert detectives here.

We are unable to get audio through the right channel main (ATC) speaker, when routing through the subwoofer (Yamaha HS8S).

Signal path:
• Dangerous Monitor ST -> D-sub to XLR snake ch 1-2 -> HS8S L-R -inputs • HS8S XLR outputs -> XLR cables -> ATC mains

I've tried swapping cables, replacing cables, replacing cables (including the D-Sub), cleaning all connections with electronics cleaner, etc.

The sub is not passing that right channel audio to the mains. Actually, the sub seems to not even be receiving the right channel signal from the ch 2 cable. That is, the sub itself is playing nothing from that channel (tested by only connecting that channel; when the other channel is connected, you hear the low frequency output of the sub).

Swapping the XLR input cables on the sub moves the problem to the other sub channel and the other (i.e. left) ATC main. So the problem "follows" that ch.1 cable. This would suggest that the problem lies with the cable or something upstream from it (the Dangerous, or the snake).

However, there are confounding factors against that theory:

• If we connect Dangerous 1-2 the same way (same snake and cables) directly to the mains (instead of through the sub), we get sound on both channels! So the Dangerous channels 1-2 working fine, and both channels of the snake and XLR are passing audio.

• Similarly if we connect Dangerous 1-2 to different speakers (e.g. the amp for NS-10s), there is sound on both channels.

• So the problem does not seem to be the Dangerous, the snake, or the cables. (I tried different snake and cables anyway; no improvement).

• If we connect a *different* dangerous output pair (3-4 or 5-6) via the snake and same cables to the sub (and thus the ATC mains), both channels work fine! So that suggests both the inputs and outputs of the sub are working fine, and the ATCs are fine.

So it's only the particular combination of channel 2 to the sub that doesn't work.

More confounding factors:
• Using an XLR-TS cable (instead of XLR cable) from snake to sub solves the problem (not ideal as that is not a balanced connector), we hear both channels through sub and in the mains.
• "Splicing" in an additional XLR cable (that is, so the signal chain is Dangerous 1-2 -> XLR cable -> second XLR cable -> sub -> ATC mains) also solves the problem!!

After spending hours troubleshooting this, we are at a loss. Any explanation for what is going on?

Thank you for any guidance.