interesting.... when I look at Elac's home page, for example CC241, they recommend to use "Large" for Home AV Surround system. here is what they say:
"When the CC 241 is used in a surround sound system the digital AV amplifier's loudspeaker option should be set to “LARGE”. However, should additional bass be required through an active subwoofer the amplifier's option be set to “SMALL” and the crossover frequency set to a maximum of 50 Hz. If the crossover frequency cannot be set this way, the CC 241 should not be set to “SMALL”."