Radio Shack, To Calibrate Your System A necessary item to calibrate your system if it does not have auto calibration with a microphone. The Reference level is 0dB on your pre-amp. With 0dB as reference level you adjust each speaker to 75dB using a test disc and the Radio Shack or simular device. Adjust the Radio Shak this way: Range: 75db Weightning: C Response: Slow ...And you master level at 0 Pictures of a Radio Shaek sound level meter Visit Radio Shack More Calibration Stuff, Test Discs And More, Click Here Back To Technical Main E-mail us with your favourite products etc and we will add it to our site/archive..