linuxaudio.org

On 12/29/2012 02:54 PM, Fons Adriaensen wrote:

quoted text
> A directional mic can give quite a bit more than just a few dB of added

>> headroom before feedback.  Take a look at the frequency response charts of

>> the 'standard', the SM58, which pretty much has 10dB down across the

>> board.

> True if you consider only the direct sound, which may be valid

> in the case of monitors close to the mic. OTOH, if the feedback

> is mainly due to indirect sound which will come from all directions

> then a cardioid provides just 4.8 dB advantage. Which of course

> could make a difference. 

Possibly true, but consider the fact that a floor wedge is the loudest

source reproducing the mic signal.  The monitor (or monitors) will

typically be at 110-120dBa, and aimed directly at the back of the

microphone.  You can easily use the polar response of the microphone to

reduce feedback.  For example, an SM58 has the best rejection at about

160 degrees off axis.  A hyper-cardiod, such as a Beyer M88 has the best

rejection about somewhere around 120 degrees off axis.
An omni-directional mic is unusable is any situation where that mic is

being fed into a monitor system, unless the source is at least 20dB

louder than the monitor signal, which MAY be the case if you're micing a

guitar cabinet, since a) the cabinet would be close-miced, and b) there

probably isn't a monitor aimed directly at the front of the guitar cabinet.
It would NOT be suitable at all for vocals, or when you're micing horns,

acoustic guitar, violin, etc.

It would also be complicated if you are using side-fills, as is

typical.  Of course, it's also complicated by stupid things such as

whether or not the lead singer decides to put on a hat!
I mixed monitors for many many years.  It's far more complicated than it

would appear at a casual glance.  You get 8-10 on-stage monitor mixes,

running a total of about 100,000 watts (including sidefills), and

there's a lot going on.
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