Are all web sources you are recording like this, or just one?
A podcast can get this exact effect if they are using two totally separate audio sources, like using a Zoom recording where each person records their own track. It ends up sounding like you are sitting in the middle of a big room with a person talking at each end. A stereo podcast needs to be panned at about 70% crossover or 80% at maximum.
If you are recording a source that is like that, the only thing you can do is pan it yourself.
Thank you for answering. In fact, yes, I was recording through the microphone of the webcam.
I could solve the problem: on my linux everything must be set using the pavu-control (pulseaudio, control) : we have to choose what is the input source (line or monitor of the audio) and set the recording input level.