I was playing my five string through a 112 cab and found that playing on the B string caused the speaker to make fluttering sounds, regardless of how I set the bass controls and amp settings. I hadn't used the F-1X cross over before (I had been using the full range out), but thought I'd try it to see if it would remedy the situation. Not only did it solve the problem, but it opened up a whole new pallet of sounds to work with between the preamp and the Series bass electronics.
I ran the bass mono into the F-1X preamp. I ran the low pass out from the F-1X preamp into channel 1 on my power amp (QSC GX7), and ran the channel 1 speaker out to the 112 cab. I then ran the high frequency out from the F-1X into channel 2 of the power amp, and ran the channel 2 speaker out to a 115 cab. The result: only higher bass frequencies go to the 112 and low frequencies go to the 115 cab.
I set the low pass frequency cut around 98Hz, and set the high frequency boost around 1. That not only fixed the 112 fluttering problem, but WOW does it sound great! Also, minor adjustments to the filters and CVQ switches on the bass are much more noticeable.
I will experiment more with this set up, but boy am I happy!
