In my opinion the N8 was one of the last Nokia phones to have a decent speaker; but of course the awkward placement on the back of the phone didn’t help. After that the Lumia 800 has a pitiful excuse of a speaker, and the Lumia 900 although better still wasn’t up to par with the past; let alone the iPhone 4S which has a very impressive loudspeaker. The Lumia 920 changes all that and brings sound back, the speakers placed on the bottom of the phone (same placement as the 800 and 900)
is actually two speakers as far as I can gather (Actually the ports on the bottom of the 920 come from one single speaker source, separated by a “wall” into to different outputs- thanks to everyone who pointed that out), meaning that it outputs audio in stereo rather than mono; making it the only one of the three to do so. Even though the 808 records in stereo with rich recording it only out[puts from the one speaker near the camera bump in mono, however the big camera bump also provides it with larger “air space” which is essential for louder outputs.
So check out the video below and see for yourselves:
As far as I can make out the 808 and 920 are almost tied in terms of output volume (if not then the 808 is slightly louder, but nothing significant).