Hi WTIerney,
thanks for you reply!
The most important thing is that you speak/sing VERY CLOSE to the microphone (maximum distance 4 - 5 cm from your lips).The microphone should be placed right in the middle between your T4 speakers and as far away from the speakers as possible.
The SM 58 has a
cardioid polar pattern. This means, the monitor speaker normally should be in the BACK of the SM 58. If you have problems with
feedback, I recommend to use a Shure Beta 58A. This microphone has a
hyper cardioid polar pattern, which is ideal for using with TWO monitor speakers, placed as on Tyros models. Besides, the Beta 58 A has a "fresher" sound and a much higher output than the SM 58.
The next thing is to set the MIC GAIN to a proper value: Reduce the Mic Volume in
Mixing Console and set Mic Gain to a value that the LED is GREEN or YELLOW but NOT RED, when you speak/sing into the microphon "as loud as possible" for a short time. Then you can set the Mic Volume in Mixing Console (Balance Display) to the desired value.
To make the MIC EQ settings, I recommend to turn off the Mic Effect(s) first. Best is to cut low frequencies a little and use not too much high frequencies. The most important are the MIDDLE frequencies. Simply change the EQ settings slightly and use your ears.
Important: If you use MIC CMP (Compressor), feedback can occur earlier.
Hope this helps!
Best regards,
Chris