I recently 'lost' the sound output to the speakers on my EE; however, headphones worked fine including being able to adjust the volume control via the hardware switch. The sound was enabled (1EE_Settings_Sound.jpg), still no speaker sound.
So, I started removing recently installed apps and checking "Dev Tools" and "Spare Parts" settings; to no avail. After reinstalling Elixir (2EE_Elixir_Main.jpg) inspection finds there are more sound settings (3EE_Elixir_Sound_Settings.jpg) then available from Sound/Settings/Volume.
The following table is a result from experimenting with different Elixir settings as well as identifying which Elixir setting corresponds to EE/Sound/Setting/Volume setting;
Elixir...............
EE/Sound/Settings/Volume
Alarm................Alarm
Music................Media
Notification........Notification
Phone Ring.........System Volume
System..............No corresponding setting
DTMF Tones.......No corresponding setting
Voice Call...........No corresponding setting
However, DTMF Tones and Voice Call:
Change one and the other automatically changes
AND mutes the EE speakers but does
not change the Sounds/Settings/Volume display
AND leaves the headphones active.
Therefore, if speaker sound is lost and headphones are active; install
Elixir 
and check to see if DTMF Tones and Voice Call are muted.