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Line level input on Polycom HDX 9000: messed up sound on far-end


Line level input on Polycom HDX 9000: messed up sound on far-end



I am having problems with the line-level input of the Polycom HDX. For my current application, I am using a mic processor (ClearOne XAP) that mixes 4 microphones in the room and outputs the signal at line-level. I have wired two mono phoenix connector outputs from the XAP into 2 x RCA male connectors and I can capture that signal using a capture card. The signal coming from the XAP is fine, the audio quality is good as expected. I use that output for recording all the time so I know that whatever comes out of the 2 RCA on the XAP is a good quality signal that I am happy with.


I am trying to feed that signal (that I know is good quality) into the Polycom HDX using part number 2457-23492-001


In the Polycom settings, I set the input as line level (i.e. not mic-level) and set the volume to 10 as that's the only level that gives acceptable volume on the far end. Regardless of the acceptable volume, the near-end audio seems muffled and unclear when listening from the far-end. It is certainly not as good as whatever comes out of the XAP. I have also tried wiring XAP outputs directly into Polycom's inputs and the results are the same.


Does anybody have any ideas what I'm doing wrong and why the Polycom messes up a perfectly good audio signal?




Message 1 of 3
Trusted Contributor

Re: Line level input on Polycom HDX 9000: messed up sound on far-end

From Polycom AV consulting engineers:


Not enough info…
But the XAP is a room echo-canceller with all the features/functionality of same.

The HDX9000 has an internal AEC.


If the two are not connected correctly (i.e. HDX is not providing the AEC reference to the enabled AEC in the XAP or the XAP and the HDX echo-cancellers are being run in series) then bad audio is the result.

Clue that something is really wrong…
input gain set at 10 on an HDX means that there is very little signal being fed to it.

Where is the HDX audio meter under this condition?

Message 2 of 3

Re: Line level input on Polycom HDX 9000: messed up sound on far-end

The Polycom clearly processes the sound so yes, I also assume that it's double AEC.


The meter on web gui goes over red when it's set to 10 but the volume on the far end is still not very loud.


Is there a way to switch off AEC on the Polycom and leave it for the XAP, i.e. connect Polycom's output to XAP's input, then route it to XAP's outputs and choose those outputs as AEC reference? I have tried everything in the audio section of the Polycom's web GUI to no avail. Is there a better way of connecting the XAP to the HDX, e.g. using expansion ports?



Message 3 of 3