Audio mixdown taking too long?

So, I have a fairly simple scene of moving low-poly objects (8), it’s 10 seconds long / 300 frames. Each has their own speaker that plays a specific sound.
I’ve started the mixdown with default settings (1024, flac) and on my 2600K CPU it has been 4 hours of cpu time (half an hour) and it’s not done.
Is this normal? If not, how can I debug this?

Thanks for your time

So what are your scene and render settings ?
Without this basic info everyone else is in the dark just like you