Kan man ikke vælge, at man har store fronter samtidig med man har sub på?

Jo, men det anbefales ikke. Klip fra manualen side 24 - læs selv videre:

"ENHANCED BASS
When the subwoofer is set to ON and “Front” is set to “Large”, Enhanced Bass is also available. Normally, with speakers set to “Large” the subwoofer is not
active. The Enhanced Bass option allows full range operation of the speakers with the additional bass contribution of the subwoofer. This feature is
particularly useful when one wants to experience maximum bass output. Please note that due to acoustic cancellation effects, the bass response may be
uneven when using this setting
You can set Subwoofer to “On” even with “Large” front speakers, in which case bass content from any channels set to “Small” will be routed to both the
subwoofer and to the front speakers; LFE-channel signal will pass only to the sub. In most subwoofer-equipped systems, setting front speakers to “Small” is
usually the better option.
All the speakers’ low frequency content can be directly adjusted within the range 40Hz to 200Hz.
NOTE
The configurations set forth at “Speaker Setup” are carried over whenever it is enabled during A/V Presets setting. Please see also the section “AV Presets”
for reference."

Anker
Tak :)
Selvom jeg ikke helt forstår det.

Jeg formoder du har manualen, hvor du kan læse mere om det. Ellers kan den downloades her:

http://nadelectronics.com/products/av-receivers/T-757-A/V-Su rround-Sound-Receiver#heading-downloads

Desværre ikke på dansk - men du kan få den på svensk, hvis det er sproget der driller