large room teleconferencing?

klaasvt

Member
How do you connect a phone line to your house PA system (using an aux send as the input, and running the output through your mix desk to the mains)?

I have a situation where I need to run an interactive teleconference from a large room (up to 500 people). We have an ingenious but aging hand-made box now (using speakerphone parts and some filtering circuitry), which has worked for the last 15 years... now it is getting old and unreliable, and the the guy who built it is not going to try again. What is the modern solution for this? It would need to connect to our PBX via an analogue or SIP line.

Any thoughts? Advise? Ideas?
 
"Telephone hybrid" and "mix-minus" are your friends.
 
We have the set-up right on our desk, sending a mix-minus back to the phone, but what I'm looking for is the actual device, the actual phone, that can connect to the phone line and has inputs and outputs for me to connect the feed to and from the desk... seems simple but so far I'm unable to find something that will do that. Maybe I'm just typing the wrong thing into Google?
 
If you have an analog phone line, that you can plug in a plain, old telephone into, then the following are my suggestions:

https://www.bswusa.com/Hybrids-JK-Audio-AutoHybrid-P3060.aspx

https://www.bswusa.com/Hybrids-JK-Audio-Broadcast-Host-P3079.aspx

The difference between the two, besides the price, is the amount of isolation (hybrid null) you can get between send and receive. Without a good null, someone speaking locally will sound tinny in your sound system, because some of the send audio comes back in the receive port.

If you have a digital telephone system, that only accepts proprietary telephones, then interface to the handset cord with one of these:

https://www.bswusa.com/Couplers-EXCALIBUR-HA-1-P2259.aspx
 
I've always used these types of systems in the past because that was the norm.
But has anyone ever tried Skype or Google Voice?
Seems like in the age of "HD voice" and other higher quality audio codecs, we'd be able to avoid analog POTS.
 
Yes, I've been wondering the same... The suggested devices will dot he trick (if they work in the UK!), so thanks @FMEng for that, but I would love to go digital somehow.... Of course, the other parties would need to support that. Bit this is a really good start!
 
I have quite a bit of experience with Zoom, and it can sound very good. The limitation is usually the mic at the remote end, because the "sound array" mics in laptops and camera mics are terrible. Wireless earbuds often have terrible sounding mics, too. Wired earbuds generally sound good. I send out my favorite, cheap headset, the Logitech H111. It uses an omni mic, which avoids plosives, and has smooth frequency response. Too many headsets are noise cancelling or directional, which adds a multitude of problems. I pair the H111 with a headset to USB converter, which eliminates driver issues (Dell sound garbage). The whole setup costs less than $30. (Note that the Logitech H110 is NOT the same.)

Logitech H111

AkoaDa converter

The computer for the sound system will work best with a decent, USB audio interface with balanced, line level inputs and outputs. You could get away with taking the output through a DI Box, and using the computer mic for send audio, provided the computer is close to the local person speaking.

If you want to get really picky, Zoom has a setting called original sound, which uses a better, stereo codec, and turns off AGC, gating, etc. Use it for feeding music, but leave it off for two way voice. I used original sound for streaming orchestral music, and it was good.
 
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If you must use a VoiP connection.... I've not used the JK Audio box above but have used and own a pair of Gentner MicroTel interfaces, where the handset cord in\s plugged into the MicroTel and it emulates the handset. It's a small mixer, basically, that replaces the handset.
microtel.jpg
 
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The Gentner is essentially the same gizmo as the Excaliber I linked to. Gentner is a company that is long gone. They made a few successful products and some junk.

I had a Gentner hybrid that had a designed in hum. The flat power transformer magnetically induced current in the metal chassis, causing hum in audio circuitry. Every time I had it on the workbench, it tested clean, but it hummed in the studio. I finally figured out it only hummed with the lid installed. Insulating the lid, from the chassis, with tape, was a fix that made it usable until Telos came out with DSP hybrids that outperformed everything.
 
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Thanks all for the good input. I'm in contact with bsw now and I think I'm all set! The digital hybrid is going to work great.
 
Just to close this one out, we went with a couple Sonifex DHY-04 hybrids, they are not the cheapest but work really well.
I trialled a JK Audio hybrid, but that thing produced a hell of a hum into my system, it sounded like an air compressor running... Not a ground loop, it sounded like something internal. Anyway, the Sonifex is working great and their customer support is just flawless. Officially recommended!
 

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