Yes, external speakers may be used if required. However, because the echo cancellation of the HDL300 system has been tuned for its own built-in microphones and speakers, optimal audio performance may not be achieved when external speakers are used.
When the output jack is connected to an external speaker, the output audio must be configured using Nureva Console (see the Using auxiliary ports article). If Nureva Console is not set properly to “Speaker out,” but rather the default “Microphone Output,” then disruptive audio feedback can occur.
In the speaker out mode, the internal HDL300 system speakers will be disabled and the output will only be played over the external speakers connected through the analog output port. Because the analog output port is used for the external speakers in this mode, the UC&C connection must be made through the USB port and cannot be made through the analog ports. The USB connection will still be the communication link to the HDL300 system’s microphones and the far-side connection in this configuration.
The analog output port is not intended to directly power an external speaker and would need to be driven through an amplifier. The amplifier should have a fixed gain. If the amplifier can vary the gain, then the gain should be set to one value and not changed (especially when using the product). Varying the gain using the external hardware amplifier could cause the calibration settings to be invalid and reduce system performance. The speaker volume should only be adjusted within the application software or operating system.
The amplifier and speaker should have a reasonably flat gain over the voice band frequency (300Hz to 7Khz) for the best performance. Equalizers or speakers that result in unlevel gain will cause degradation in the echo cancellation performance. Avoid any bass boosting amplification (in the 50Hz to 300Hz range), powerful bass speakers or equalization schemes, which will cause an uneven frequency response.
The output for the external speakers will only be monaural (mono), despite any settings in Nureva Console or the source of the signal.
The external speakers should not be installed close to the microphone and speaker bar, nor should they be pointed in its direction. Direct coupling from the speakers to the microphones will cause issues with echo cancellation.
Once the external speakers are installed, perform a fast calibration with the HDL300 system to configure the new setup.