Telos NX12 user manual Feedback Control

detailed configuration & reference  73

larly useful when the caller is carrying on and the talent wants to interrupt to move the show along.

♦♦ Reduces feedback when a loudspeaker is necessary.

♦♦ In the loudspeaker case, reduces audibility of the caller signal that couples through the acoustic path, into the microphones, and is returned the caller resulting in a more natural sound for the caller.

The duplex system inserts a controlled loss (ducking) into whichever audio path (send or receive) is not active at the moment. When the caller is speaking, this loss is inserted in the announcer path, when the announcer is speaking the loss is inserted in the caller gain is reduced. The effect is somewhat “seesaw-like”. If Feedback Reduction in the Audio menu is enabled, the Nx12 will increase ducking in the announcer-to-caller direction.

As a guideline, you will need more ducking when using open speakers. This helps reduce the oc- currence of feedback and, also reduces the chances of the caller hearing himself via the speaker to mic path, which has an unnatural quality and can be disturbing. In a morning zoo type of scenario the setting should be even lower as there will typically be multiple mics used with open speakers. Fortunately, this scenario coincides with a more duplex style of operating – where pre-recorded ‘bits’ may be played to callers and must be heard without interruption. The default setting is 7.

You may choose how much of this effect you prefer, from Half Duplex (16dB) which makes the Nx12 operate like a one-way-at-a-time speakerphone, to Full Duplex (0dB) which disables ducking. A good starting value would be 6dB.

Feedback Control

We’ve carefully designed the Nx12 so that problems with feedback should be rare. However, despite excellent trans-hybrid loss and a number of other features, you can probably induce feedback if you try sufficiently hard, such as by cranking up your studio monitors to very loud levels. Some suggestions for what you should do if feedback does occur follow:

♦♦ Enable the Feedback Reduction function.

♦♦ Adjust Caller Ducking to a higher setting (more ducking).

♦♦ When mic processing is used, connect the hybrid in such a way that it gets an unpro- cessed mic signal.

The problem here is that the mic processing combines with the Nx12’s internal AGC to increase gain in the feedback path. Depending on the processor used, the feedback margin can be reduced by many dB. The Nx12’s internal AGC has a internal adaptive smart-gate function to prevent inappropriate gain increase, but it is thwarted by this additional processing.

If it is not possible to get an unprocessed mic signal, try to set the processor in such a way that room noise is not “sucked-up” during pauses. You can also try reducing the output the mic processor or set the Nom In (Nominal Input Level) selection in the Audio menu to the next higher setting, thereby reducing levels into the unit. The level to the caller should be OK since the Send AGC will compensate, however you will force that AGC towards its maximum gain, and thereby reduce how much gain it can add to the feedback path.

♦♦ Try repositioning the mics or speakers. It also helps, of course, to use directional mics. Customers have reported good results with cardioid mics such the EV RE-20 and the Shure SM-7.

♦♦ Add equalization to the monitor path. Acoustic resonances usually result in pronounced peaks in the feedback response. Since there are likely to be only a few pronounced peaks