Steve, my wife is normally my co (non) pilot. She has never mentioned that the com volume was low. Each time another pilot has flown co pilot I had to turn my com volume (i.e. GTN com one) from 43 percent to 52 percent. I thought my hearing was just better but not so. Things finally added up and I realized pilot side level was higher. Stein did the panel, head phone plugs were wired by me. If by chance the schematic had wires reversed could this cause the issue.
Rich,
I also have a GMA 245 (great audio panel!). If I put my Zulu headset on, and plug it into either the pilot or copilot headset jack without changing anything on the headset, including the way it sits on my head, the COM radio volume sounds the same.
If you change the person, or the headset, using the copilot position, chances are good that things will be a little different for that user. Even the way the same headset fits a different person can make a difference.
I will also occasionally (but not often) have a passenger (typically a pilot) who says they can't hear the COM radio even though I can hear it just fine, and I know that I could hear it just fine in the copilot position. No problem, it is easy to accommodate this request to turn up the COM radio volume.
99.9% of the time, I have the volume controls on my headset set to max. The audio in my plane is setup that way, and when I want to return to the audio configuration (including alert audio) that works the best for me, it always starts with making sure my headset volumes controls are at max setting to remove that variable.
Step one to accommodate a passenger requesting more COM volume is to make sure that their headset volume controls are set to max. If not, their request may be met by doing just that and turning down the intercom volume with the copilot dedicated volume knob if needed.
If that doesn't address the issue, turn up the COM volume until it meets the passenger needs, and adjust your headset volume down until you are comfortable with the new COM volume level. Adjust your intercom volume to your liking with your dedicated knob to match your new headset volume level setting. All done.
Steve