Spark Room Kit Plus with audio DSP and external mics

[sduea2011]

We recently installed a Spark Room Kit Plus with a Tessira BiAmp audio DSP and Shure MX396 table mics.  I know the Spark kits are not designed for this configuration, but it happened.  The audio quality to and from this room varies almost daily.  We test and get it sounding good.  A day or two goes by and I get reports of poor audio.  There is a very loud HVAC system feeding this room so that's comes into play too. We turned AEC off on the BiAmp and enabled Echo Cancellation on the codec because that HVAC noise was greatly reduced.  Again, I know this shouldn't be set up this way, but the BiAmp just isn't able to do the job.  Recently the incoming audio to the room sounds robotic at times, digitized.  From the far end, there's often echo.  The incoming audio sounds better with the internal speaker on, but we need to use the ceiling speakers in the room.  When internal speaker is on, there is echo heard by the far end.  Outgoing audio levels raise and fall noticibly.  It wasn't like that when we set it up.  It seems the audio issues both directions are different every time I work on this room.  Has anyone tried connecting a BiAmp to a SRK+?  Codec is currently running CE 9.2.$ and it's registered to VCS-C.

[Enrico Conedera]

A Tesira should work just fine with a Room Kit Plus.  Or a Room Kit, Room 55, or Room 70.  All of our new codecs support use of third party microphones and audio systems.

In this case, you apparently have a nasty noise problem with the air handler.  Have you measured the ambient noise level at the tabletop?  There are smartphone applications for this.

"From the far end, there's often echo"...If you are hearing echo from the far end, that is a problem at the far end - usually gain structure. 

"When internal speaker is on, there is echo heard by the far end"...You should verify your gain structure with the Biamp as well - you want unity gain at all interconnecting points.  Remember that you have to send microphone level at nominal -35dB from the Biamp to the codec; you can't use line level +4dB.  A simple 40dB audio pad from Whirlwind can be used to match the levels.  Usually echo is caused by improper audio levels between components.

[sduea2011]

Thanks for the reply.  We have installed a few of the spark kits, or whatever they are being called today :) and I usually need to deactivate the internal speaker if we are also routing through the ceiling speakers.  We get echo when they are both on even without a BiAmp and using cisco mics. I'll check on what's used to get the audio to the ceiling speakers to see if we can make any adjustments.  We only have one SRK+ set up with a BiAmp and external mics.  We working on that unit on Friday and had it sounding really good in both directions by the time we finished.  Lots of BiAmp adjustments.  What do you suggest for the codec mic input level to be set at when using a BiAmp?  Default? 

[aclayton59]

I am having problems with a similar set-up, except with a Shure MXA910 Ceiling microphone array. My problem is, as soon as I plug the output of the Biamp into the spark codec (microphone in port 1), the audio level coming from the Spark speakers drops dramatically. I have the requisite 3.5 mm TRRS connector terminated as follows: T(+), R1(-), R2 (not connected) S(Ground). I have tried, reversing +/-, Disconnecting the shield, and installing an isolation transformer, and using a different output on the Biamp. None of this has made any difference. 

Any Ideas?

[emiliolara]

Have you guys found a solution to this?

Regards.

[Wayne DeNardi]

From years of doing this, I'd highly recommend that you leave the codec mic input level at the default setting (makes it easier if you need to reset or replace the unit) and that you turn echo cancellation OFF on the Cisco endpoint.   You should then do all the Echo Cancellation on the Tesira using the Tesira's AEC inputs for the microphones. 

[emiliolara]

Thanks