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Rising star

Question on the AudioScience Mic and an SX20

Have a customer that purchased the SX20 for a Training Room and also the AudioScience Ceiling Mic.

Getting ready to install and we find that the Audio Science has a 3 prong connection that would work for a C40 but not so well for the 3.5mm mic jack in the back of the SX20.

Is there an adaptor that will allow the mic to work with the SX20?

Enrico Conedera
Cisco Employee

Hello -

Revolabs makes an adapter specifically for C20 / SX20.  They use it for their HD wireless microphones.  It is a short, XLR female to 4 conductor male 1/8", adapter cable.  cable p/n: 07-XLRTO35M4-01

However, that is not sufficient in itself.

The AudioScience mic uses a Crown PZM element, which requires phantom power, and has an output rating of somewhere around -43dB (not certain of that figure).  This is typical for a condenser microphone, and it is a bit too soft for the SX20.  The input specification on the SX20 mic input is -35dB.  This means that the AudioScience won't be loud enough.

So, two issues:

1) You are going to need phantom power.  The SX20 provides 12V +/- 1V phantom power, which is not enough to power third party microphones.

2) You are going to need to boost the signal by at least 7dB, or possibly more, in order to have sufficient output from the AudioScience into the SX20. 

So you need a mixer or other signal booster, that includes phantom power.

If you have that part figured out, then the Revolabs adapter can be used.  Or you can make up your own adapter cable from XLR to 4-pin mini 1/8", using the pinouts provided in the latest SX20 Admin Guide, which can be found at

Keep in mind that the SX20, like the C20, was designed as a plug-and-play device, rather than an integrator's codec.  So there are challenges around using microphones other than the provided ones.

We are facing echo problem while using Revolab Mic model HDDUALEU & Fusion 8 channel model with SX20. Is it a compatible issue or we are missing something.

you may not be facing an incompatability issue but a timing issue between the mic, the codec and the speakers.

Are the speakers directly connected or are they part of the monitor?

If they are part of the monitor there is likely to be some processing that the monitor is doing and that is why you have the echo.

Under Configuration ==> Experimental there is Audio EcReferenceDelay

This is probably set to 0.  modify this to account for the minisec delays that the monitor is injecting so that the system is accounting for the delays in its echo cancelation calculations.

Hope that this helps.  A tip from others.

Thanks for the reply.

The Speakers are part of Monitors.

When we changed the value of Audio Eco reference delay there was no echo but if the system is switched off and on again the eco is back and again you have change the value which is not acceptable by the users.

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