Serious Feedback - Mic Mechanic 2 / Bose L1 Mk 2

Contributor - Level 1
I am a solo performer (guitar/vocals/backing tracks) using a Line 6 pedal (guitar - channel 1) and a Shure SM58 into a TC Helicon Mic Mechanic 2 (vocals - channel 2) and backing tracks via iPod (channels 4/5) into a L1 Mk 2 with 2 bass modules and ToneMatch T1. I am experiencing serious vocal feedback problems and hopefully you and your team can offer some suggestions as to a possible solution.

The situation is that whilst singing, playing guitar and having the backing tracks playing there is NO noticeable feedback noise whatsoever BUT as soon as I end the song and attempt to speak / introduce / make conversation etc the amount of feedback is unbearable. I have tried various positional changes to mic and the L1 and bass modules placements but it doesn't reduce the feedback. The microphone is positioned well behind the Bose system/speakers. The only way to eliminate the feedback whilst speaking is to turn down the master volume of the ToneMatch (ie PA) which is not very satisfactory - but I don't know what else to do ??? I am very aware/careful regarding input trim settings etc and fully appreciate their significance.

I am definitely no expert regarding EQing etc etc but have been advised that setting appropriate EQ frequencies could reduced/eliminate the feedback - I just need a solution. Could the Mic Mechanic 2 vocal unit in some way be creating the problem as it does have non-adjustable preset inbuilt effects eg Compression, EQ etc. As I said above there isn't a problem during a track performance it's only when a song/track has ended and then a couple of seconds later as I attempt to speak/introduce the next song feedback kicks in at an unbearable level.

Any help/suggestions would be greatly appreciated. Thanking you in anticipation.
Very kind regards,

Re: Serious Feedback - Mic Mechanic 2 / Bose L1 Mk 2

Triber Moderator
Hey Rod,
Sorry to hear about your feedback issues, I really appreciate how well written your post is and the details you've provided. I do have some more questions though...

Are you using an electric guitar, or an acoustic guitar? If it's an acoustic, what kind of pickup is in there?

You mention that your "microphone is positioned well behind the Bose" - I'm wondering exactly how far? I dug through the Bose forums a bit and they recommend keeping your sound sources (like the microphone) "5 or 6 feet away from the tower."

Can I ask you to please walk me through your gain staging? Your trim and output levels?

Have you dipped into any EQing yet or is everything pretty neutral so far?
Spencer Larsen - Testing Engineer @ TC Helicon, MUSIC Tribe. Our Support Team is always available for more urgent assistance.