After I activated a loudspeaker in the project data module nothing happens. What did I wrong?

There are two ways to activate items for use:

1. Use the Items menu
2. Pick an item and use the RMB to activate or to deactivate To see which items are activated in the current project make sure that in the Options Window under Items Tab the column labelled "Act." (for Active) is showing a "Yes" for the selected item type (In this case the loudspeakers). Otherwise LMB click on "No" to change. Press the OK button and then the Room will be redrawn using the colors for active items, chosen at exactly the same place.