So this fall, as usual, I’m the audio engineer for a three-day conference in Salt Lake City with several hundred attendees, and about three times that number listening live online. While the quality seems fine, I’m looking for alternatives to bring the best experience to listeners.
Here was last year’s setup:
- Two laptops: one Windows, one Linux.
- Windows laptop runs Cakewalk Sonar, recording an archival-quality 16-bit, 44.1KHz stereo feed from a combination of various mics. I think the only change I’ll make this year is to give the room mics a bit more boost so that the audience sounds as large as it is… last year’s recordings sounded like there were maybe a half-dozen people in the room.
- Linux laptop runs BlackICE pumping audio to an ICECast streaming MP3 server over the hotel’s wi-fi link. This is a live feed, and ran all weekend long with only one hitch.
- Mackie twelve-channel mixer.
- Podium mic and two condenser room mics to provide atmosphere.
- Two wireless hand-held microphones: one for presenters who prefer to walk rather than stand behind the lectern, a second one used by my gofer to field questions from the audience.
- One wireless body mic; I’ve never been very impressed with this one. It just sounds muted compared to the high-quality hand-held stuff and lectern-mic. These days it functions as an adjunct mic in case I need to separate the room feed from the online feed.
- Line-in from the AV stand next to the projector for multimedia presentations and movie showings (last year, I had a nasty ground loop on this line; I think I’m going to make this link wireless so that I avoid that particular electrical phenomenon. You can’t get TRS-balanced output from a laptop.)
- During downtime, I would compress and upload archival audio to the web site. This is a very labor-intensive process that I’d rather save until a few days after the conference, but I’ve done it for the past three years.
Now, this year, I’m thinking that I should have a similar setup, but with a totally new twist: Blog Talk Radio. This site would allow me to schedule the presentations in advance, provide automatic archiving, as well as allow call-in telephone numbers and an online chat room to field questions for Q&A sessions.
This would require a third laptop, but I could have my assistant screen questions on the chat room and announce them to the guests in the ballroom during Q&A, or even have the call-in on the sound system in the room (though, of course, we’d have to ask them to turn down their radio and pay attention to the phone instead).
The huge plus-factor for BlogTalkRadio, for me, is that I’d already have an audio archive of the sessions online, created real-time while we’re recording. This would save me the step of having to compress and upload the archival recordings during the session, so that I could hang with other guests and take a potty break now and then. A few days after the conference, I could store the MP3 archives on the web site like usual.
Any alternatives that might work better, or enhance the experience?
Additionally, I’d love advice on how to avoid the ground-looping problem on the long line from the laptop to the mixer. That 60Hz hum is obnoxious. My initial thought is to go buy a line-level wireless transponder. My second instinct is to keep the laptop up next to the presenter, use a long VGA cable, and have a mixer with a balanced output up at the presentation-table. This setup would let me use a balanced connection for that long run, and, with luck, eliminate any ground-loop issues. Or, maybe, I should just go buy a Direct Box.
Showstopper with BTR
Looks like I ran into a couple of show-stoppers for BTR:
1. You can’t schedule a segment more than 30 days in advance. 2. You can’t schedule more than one segment per day.
Considering these things run all day long in 3-5 segments… yeah, unless there’s a work-around, BlogTalkRadio is out for pushing this broadcast. I could always fall back to BlackICE+ICECast like I did last year, I suppose.
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Matthew P. Barnson
Have Ye Read This?
I found this through Googling: http://www.epanorama.net/documents/groundloop/
And as for the archival process, there has to be a way to automagically script it so that your audio files are compressed and stored somewhere. I know LAME has command-line functionality, for one.
I would assume the process would go a little something like this: -> You’re storing audio file realtime. What causes you to stop recording to one file and start another? A break in presenters? File size? Audio length? -> When the file is complete (no more audio being stored), then it would be compressed via MP3 or some other audio compression format -> After compression, it would upload the file to a website
Sound right? If so, we should be able to knock that out.
My $.02 Weed
Ground loops and more
Great reference, thanks! I realized that I resolved my ground loop and erratic power problems in my home studio through the use of two UPS units. I just need to pick up replacement batteries for a spare that I own, and that might resolve the dirty power problems right there. I’ll need to budget a bit more time this year with the complete setup installed before people show up in order to make sure I have the problem cornered.
Well, my workflow is like this as of last year (ignoring the streaming-audio portion):
I’ve always been able to just barely squeeze that in in the 15 minutes or so between presenters. As my laptops have gotten faster, it’s gotten easier 🙂
My train of though is that perhaps I should invest in an outboard effects unit to take care of compressing the signal before it hits either my recording rig or the BlackICE streaming laptop. I could also eliminate all the “working with the archival audio” portion if I were to set up BlackICE to dump audio to disk as MP3, then stop the recording. That closes the file. Then when I restart, it opens a new file name. That way, I could just upload and then modify the web page.
OR I could figure out how to make the archive available on my ICECast server. I think that can be done, but I’m not sure how…
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Matthew P. Barnson