I just test the sound active and I have compared with a Air 3g and the Plus is much worse. Same song in both and volume to 100%.
I do not understand how two tablets manufactured with different speakers.
Should sound be same in both?
Problems with sound level: Right click on speaker icon on systray, playback devices, playback, select the device, properties, effects, disable system effects ie. Equalizer
I did it on my Plus and it increased maximum volume by about 15%