Hi
I have an L1 model 1S with a B1 bass and tone match. Ive been using it for my own gigs with great success since December 2012. Last weekend I set up for a duo, 1 guitar and two mics,. The main singer does not have a very powerful voice and in order to make her heard I upped the volume. However this caused quite a bit of feed back and I was limited in the actual volume I could use.
Has anybody else experienced this and can anyone please assist me.
Many thanks
Hi DoubleH,
I’m sorry to hear that you were having difficulty with feedback. 
Microphone Technique
Microphone technique is very important when it comes to avoiding feedback. To get the best gain-before-feedback you want to sing directly into the microphone using close-mic’ing technique. That is, with lips just barely brushing the windscreen. The ToneMatch Presets for vocal microphones are designed to work with that microphone technique.
As you move farther away from the microphone you lose tone and in this case more importantly, you lose gain-before-feedback. That is: As you move away from the microphone you increase the chance of feedback.
If you have a vocalist who tends to shy away from the microphone, turning up the gain on the T1® to compensate will cause feedback. You’ve already experienced this.
Number of Microphones
The other factor here. It sounds like you’ve gone from one microphone (for your solo gigs) to two microphones for the duo. The more open microphones you have connected to a system the lower your gain-before-feedback. That is: more microphones can mean more feedback. You can reduce the feedback if you are using close-microphone technique.
Here are some notes about Microphone Feedback in the wiki.
Gain Staging
When you set up a new singer and microphone with your T1® you want to match up the levels for the singer/microphone to the input trim on the T1®. Done correctly, this will optimize your gain-before-feedback. It is important that the singer use close microphone technique and sing loud. Note, you do NOT need to have the T1® Master Volume turned up during this procedure, so you don’t need to objectionably loud to do this.
Here’s how you do it.
Gain Staging a Microphone with the T1®
Please watch the short video below. It is for the Model I, but the principles are the same.
–== click the picture ==–
Unfortunately there is no video for doing this on the T1® but the ideas are equally applicable.
Use the same microphone technique Steve describes in the video.
The colors on the T1® are a little different because the T1® trim uses 3 colors. You want to have a good solid green signal with occasional flickers of yellow.
If you are seeing flickers of red, turn down the trim.
For more detailed notes see: T1® Gain Staging.
Does that help?
Hi ST
Many thanks for your quick reply.
You understand my problem very well.
Equally I am pretty sure I understand your answer.
I will use your recemmendations next time I set up for the duo.
I think the real key as you say is close microphone technique.
Thank you again
HH
I put multiple mics into my bose L1 classic regularly using a mixer.
The two main things I’ve found with feedback.
1. The type of mic. Some mics feed back much more easily. I find Sennheisers designed for rejection to be the best, Shures are squealers.
2. I use the eq to find the trouble frequencies and turn the down. What I do is turn all the frequencies down, and the volume to where I would like to be. Then I turn the bass, mids and highs up one at time. If it squeals it needs to be turned down a bit. At practice, for me, the main culprit is in the bass and mids. But this changes from place to place and even day to day. I can leave a set up, move nothing and the next day different frequencies need adjustment or have no problem. I dont know if its the weather or just something moved in the room.