Hello Wyatth,
Hope you are well. It is almost impossible to calibrate a sub in the store.
To ballance the sub I generally turn all the mains down as far as they can be turned down in the setup.
Turn the gain to a little less than half on the sub.
Set the receiver's crossover to 80Hz.
Disable the crossover on the sub, you don't want double crossovers.
Set all the speakers to small, no matter the size of them.
Make sure the store is using the LFE output to the sub.
Now with the mains turned down all the way, increase the volume of the receiver till acceptable bass is heard or measured with an SPL meter. Now increase the main speaker channels until they are ballanced with the subs output. Once this is accomplished you should have acceptable bass at all volume levels.
Later,
TonyM
