My issues is the F12 produces a very lose/boomy bass response,
calibrated many times. So currently have it up for sale.
the sub is boomy because you do not have it set properly. go to;http://www.avsforum.com/avs-vb/showthread.php?t=824554
and near the bottom of the first post there is a test audio section.
download realtraps, it has test tones that go from 10Hz to 300Hz in 10 second intervals.
by ear listen for clean tones set subs volume until you hear it.
be patient it takes time. boomy is because sub is set too loud usually.
now for the looseness, it is because the amp driving the sub is too high and
what you are hearing is the cone bottoming out.
patience and your ear is what you need for the adjustment. once it is set
you should hear nothing from the sub itself. no noise and vibration that is.
any low frequency noise heard should almost sound like it is coming from
everywhere in the room...that is where you are facing. when you and your
wife sit for a movie and both do not hear anything from the sub
'you have it set properly.'
PS if you live near me I'll help...