As I found for now, the only good way to have konsole beep via system speaker is setting it to run a command and making the command "beep -l <duration>". But this appears to be too slow: if I press <Backspace> key at bash prompt and hold it, I get rare beeps about 3 per second. For comparison, other terminal emulators like gnome-terminal and Linux virtual terminal repeat beep seemingly at every keypress event. So konsole lacks real good option for doing beeps. I think it'd be a good idea to place it in "Configure Notifications" dialog as something like "Beep with system speaker" (maybe with parameters like duration and frequency, but it's not necessary). Reproducible: Always
KDE has a way to make beeps instead of (notification) sounds, see System Settings > Notifications > System Bell. This is much faster than the slow sounds that travel through hundreds layers of "Linux Multimedia" </rant>. But it is also possible, that knotify itself limits the rate of notification events to prevent flood. Anyway, what you suggested should be done at kdelibs level, i.e. use this bell as a separate type of notification in the "Configure Notifications" dialog, so that you are not forced to use the bell for all audible notifications. Reassigning.