Also, the 12 kHz filter in this radio sounds great on clear
mediumwave
stations, are there any shortwave stations that have clear signals and
good audio which I can use this wide filter with (I've been away from
the hobby for a while)? Is the excellent audio reputation of the
R-1000 from the stock wide filter alone, or is the entire audio circuit

what makes it so good? If its just the stock filter, wouldn't any
receiver benefit greatly from something wider than the standard 6 kHz
filter in the wide slot?

While you get great audio with the 12 khz filter, I found it to be on
the wide side for my taste, I replaced it with a Kiwa wide filter ( 6
khz ) with little loss on the audio quality but an improvement on
selectivity.