Posting this on behalf of my friend Shaun.
Live singer with a piano keyboard and backing tracks playing through some sort of small mixer.
Dual F1 system, running out of mixer into sub, then out of sub into 812 top. Either left/right stereo, or dual mono - not sure.
Old wooden floor, sounds like the floor was raised and on foundations, so basically "hollow" underneath - but not unique, pretty standard stuff for an old venue in New Zealand.
Shaun has done about 50 shows with the F1, not a single problem until this weekend.
His description is as follows:
"The bose system has been amazing all season ...but last night i lost my confidence in it a little. I was doing a wedding.
After about 5 songs in (full on dance music) the subs started to rumble violently out of control (so they started to rumble and they got to a rumbling point where the only way I could stop it was to stop the song completely...even pulling down all low-end knobs on the eq couldn't stop it).
Very odd and now I'm nervous for next weekend.
I got through the gig by basically having the subs levels at 9 o'clock on the back panels. Has this ever happened to you?"
He's going to test the system again this week.
The only thing I could think of was mic feedback, or some sort of feedback loop - but it seems unlikely as Shaun has done 50 shows with the F1, and hundreds and hundreds with the same source set up on different speakers for years before that.
But when you're flying solo and have a challenge mid-event - you just "make it work" without really looking at some of the simple stuff. We all make 101 n00b mistakes occasionally.
Anything he could look at when he tests the rig this week, or before setting up again on the weekend?