I recently noticed that both the DQ77KB and DN2800MT don't seem to have a build-in speaker for BIOS-errors. I also could not find the standard 4 pin gnd-nc-nc-v+ connector that is usually used to connect a speaker like this:
However, I did found an "Internal Stereo Speakers Connector" on both motherboards, but besides the pinlayout being different and having two instead of one audio channel, the used connector (JS-1125-04, with mating plug JWT A2001H02-4P) is of a type that I only know from old Soundblaster audiocards, used to connect a cdrom player to the audio card.
Since I haven't been able to find speakers with that kind of connector and pinlayout, how are users supposed to listen to BIOS-errorcodes if you can't even get a speaker that can be connected to these motherboards?