Feedback problem

[FXM]

Although I realise that you probably see lots of people asking about feedback problems, I was hoping somebody could help with the particular problem that I'm having.

 

In the band that I'm in we always have major problems with feedback from the lead singers mic. She uses a Sennheiser Freeport vocal set. We've tried lots of things (moving monitors around, feedback destroyer), but nothing really solves the problem.

 

My concern is that there's something not right with the mic, and that's causing the problem. When using another mic, it seemed to increase the gain before feedback. But it can be hard to compare these things. It also seems like the problem comes and goes. Is there a more reliable method to test whether a mic is performing as it should? I don't want to return it the shop unless I'm sure that there is an issue with the mic.

 

Thanks

Neil

[boseengineer]

Is it the freeport hand-held (fp35) or lavalier (fp12) ?

 

Try a good dynamic wired microphone and see if the problem goes away. If it does, you know who the culprit is. Many wireless sets use compression, which decreases gain before feedback.

[FXM]

sorry for being unclear about that - it's the handheld mic.

 

I'll suggest we do our next gig with a wired mic. What's the reason that wireless sets often use compression?

[boseengineer]

The wireless link tends to have a pretty high noise floor (if it's analog). So they try to squeeze the inputs signal into the available dynamic range. It needs to fit between the noise floor and the the max modulation depth of the RF signal.

One way to get there is to use compression (i.e. boost low level signals so they get over the noise floor).

[flanc]

Different mic's do display different gain before feedback tendencies. Also, the room, the quality of you monitors and the power and technique of you singer are all factors. If, after experimenting with different mic's, you still have a major problem...the easiest fix is to go to IEM's for the vocalist.

[FXM]

 

The wireless link tends to have a pretty high noise floor (if it's analog). So they try to squeeze the inputs signal into the available dynamic range. It needs to fit between the noise floor and the the max modulation depth of the RF signal. One way to get there is to use compression (i.e. boost low level signals so they get over the noise floor).

 

 

That's interesting. However, in a well designed system I would imagine that an expander would be used in the receiver, to 'undo' the effect of the compressor. That would mean no impact on the gain before feedback.

[FXM]

 

Different mic's do display different gain before feedback tendencies. Also, the room, the quality of you monitors and the power and technique of you singer are all factors. If, after experimenting with different mic's, you still have a major problem...the easiest fix is to go to IEM's for the vocalist.

 

 

I'm interested in what you say about the quality of the monitors - how does this affect the gain before feedback? We currently use Laney CP10 monitors.