Mackie SP2400 Instruction Manual - All - Page 20

Using the AMBIENT MIC The ambient mic is an optional accessory (MT3100) that is available for the SP2400, which is used to sense the ambient noise level in the room. Set the AMP ADDRESS switch #8 up to enable the ambient mic, otherwise leave the switch down. The ambient mic provides an "ear" for the microprocessor to gauge the ambient noise in the room and adjust the gain of the paging mic accordingly. When the background noise is relatively quiet, the paging mic gain is at its lowest level. If the background noise is relatively loud, the paging mic gain is at its highest level. If the background noise is somewhere in between, the paging mic gain is midway between its lowest and highest preset levels. Ambient Mic Calibration and Placement 1. Connect the MT-3100 (or other microphone) to the AMBIENT MIC connector on the rear panel. Make sure the ambient mic switch is on (AMP ADDRESS switch #8 up). Locate the ambient mic in an appropriate position to pick up the ambient noise in the room. It can be mounted on the ceiling or on a wall. Avoid placing the ambient mic close to the speaker over which the announcement is being made. Keep the ambient mic away from a constant noise source, such as a refrigerator or other mechanical device that emits a continuous noise. The best placement is where the mic can pick up an average representation of the ambient noise level in the room. Note: Each zone or channel must be calibrated individually. 2. Turn off the SP2400, then turn it back on again while pressing and holding the Input 2 button. This causes the ambient mic preamp level to appear on the meter. 3. Establish the highest noise level that you would expect to have in the room using a pink or white noise source, or a music source. Input 1 is operational in this mode to use as a music source, if desired. 4. Adjust the ambient mic preamp gain trim (located just above the ambient mic connector on the rear panel, through the unmarked hole) with a non-conductive alignment tool until all the green LEDs on the meter are lit. Insure that no yellow or red LEDs are lit, which runs the risk of clipping the ambient mic preamp or ADC. 5. Press the "OFF" button when finished to return to normal operation. Paging Microphone Calibration Proce- dure (when used with Ambient Mic) 1. Perform the "Ambient Microphone Calibration Procedure" described above. 2. Switch the ambient mic OFF (AMP ADDRESS switch #8 down). SP2400 - 20 3. Adjust the MASTER VOLUME control by pressing the Up/Down buttons so the meter indicates a level at the "0" mark. 4. Adjust the PAGING MIC GAIN control as high as it will go before feedback occurs while speaking into the paging microphone. 5. Switch the ambient mic on (AMP ADDRESS switch #8 up). 6. Turn off the SP2400, then turn it back on again while pressing and holding the "3" button. 7. Release the Input 3 button after a few seconds and the third LED starts flashing slowly. 8. Use the front panel Up/Down buttons to set the lower level of the paging mic (how loud it is with very quiet background noise). It should be loud enough to be heard clearly throughout the coverage area. 9. Press the "OFF" button and the level is stored. The third LED starts flashing faster. 10. Use the front panel Up/Down buttons to set the upper level of the paging mic (how loud it is with very loud background noise). As a general rule, set this level as high as it will go before feedback (at the "0" mark if steps 3-4 above were followed). 11. Press the Input 3 button when finished to store the level and return to normal operation. 12. Verify that the paging microphone's volume is sufficient to be heard over the background noise in the room. Note: For best results, with the background noise level at a minimum, the paging mic volume should be approximately the same as the music volume. 13. If the paging microphone is not loud enough to be heard over the background noise, verify that the ambient mic is properly placed to pick up an accurate representation of the background noise. If it is, it may be necessary to readjust the lower and upper levels for the paging mic gain (steps 6-11). Using the Local Mic/LINE INPUT The MIC/LINE INPUT A and B is provided for each zone to connect a microphone for a speaker in a conference room, or similar sound reinforcement applications. If the local mic is a condenser mic, move the PHANTOM switches to the down position. Setting the GAIN When a microphone is connected directly to the MIC/LINE INPUT, the GAIN +40dB switch should be set in the down position (for a mic-level signal). When the mic is going through an external mixer, sending a line-level signal to the input, move the GAIN +40dB switch to the up position (for a linelevel signal only).