...I bought the M20d for conferences with people talking into mic. I choose the M20d for the weight, size, possibilities, and feedback control...
I do a large amount of multi-mic convention and conference work, but still had to think for a while about the best way to post something that might help you.
It seems to me that it would be very important for us to be clear about two things:
- A "routine" we need to practice until we no longer need to "think about it" and
- The difference between "Auto Trim" and so-called "automatic level control".
I'm referring to "Copy/Paste Channel Settings", as per page 10.17 of the "Advanced Guide" that arrived with your M20d and/or can be downloaded from here: http://line6.com/sup...uals/stagescape.
You will better understand why it's important for us to practice this icon-based "preset saving" routine once I've explained MY technique for handling these "conference" jobs, but for now, I'm suggesting that you spend an hour or two actually doing that practice by tweaking an individual channel to extreme settings that are very easy to "see and hear", solely so you can practice the "instant" creation (and subsequent elimination) of new "presets" to be copied to all of the mic channels we're about to use for the individuals who are participating in our "chat session".
This wonderful feature is definitely NOT meant for "on the fly level riding" of the sort we'd find useful to make our different voices more "even" in the mix.
As gordwait has noted, it is simply a very elegant way to quickly adjust for differences in the "types" of inputs we might plug in, the idea being to "hold back" the louder ones (so that they do not "clip" or distort), but apply more gain to the quieter ones, (so that they don't yield a lot of "hiss" or "system noise") BEFORE presenting them to the "channel strip rotary encoder" knobs that allow us to combine and "balance" them when we create our "mix".
My Technique For Multi-Mic Conferences.
First off, I think it's absolutely vital for every participant to be miked as close to identically as it's possible to do. That means identical mics for all, with each positioned the same distance from both mouths and large reflecting surfaces such as floors and/or desks.
The basic high-pass and eq settings should also be identical for all of these mics.
We then set the input trims (whether via "auto trim" or manually) by first wearing just one of those mics and literally shouting at the loudest level we can expect from our participants, so that our loudest shouts are "held" below clipping.
That input trim setting is then copied to the channel strips of all of our participants' mics ...and (in practice) is generally left unchanged for all such jobs where we use that model of mic.
Our next job is feedback suppression, which we pre-configure
- Via "FBS Enable" in "Deep Tweak" mode,
- With NO compression enabled and
- As "early" as possible ahead of the gig so our "room" is as empty as it can be.
Long practice has taught me that the best way is to have just one volunteer miked up and positioned in the "worst" feedback-creating position that one of our participants might adopt, but if that can't be arranged, "propping" the mic there on the best "dummy body" we can find (paying particular attention to both the mic's height and its distance from those large reflecting surfaces) is almost as effective.
We then increase that channel's gain to the point where feedback just starts to give the room's first fundamental "note" and back it off to where it just stops again ...and only NOW enable FBS and re-increase the gain until we hear the initial note be "grabbed and notched out" by FBS.
We subsequently repeat that "gain increase and notch out" for no more than two or (at most) three subsequent "notes", ...whereupon we save that as our FBS setting, ...a technique substantially different from that required for a vocalist who's typically dealing with FOH and monitors.
...you have to make so much noise that you need the room to be empty. And if you switch off the mixer, you lose every filters settings. That is a big issue for me...
You'll also see from all I've posted above that OUR main use for FBS is to "notch out" the "worst case fundamentals" imposed by a given acoustic space, something that we need to establish just once in advance of each individual "rig" or "set-up", the subsequent arrival of more "damping" (in human form) only serving to possibly reduce our reliance on the notch filtering that FBS imposes.
I'd next like to discuss "automatic level control", which we'll achieve with our compressor in Deep Tweak mode.
One main hallmark of too much compression in many jobs is "sounding fine" when participants are talking, (or singing) but feedback suddenly surprising us when the talking (or singing) stops. No amount of FBS (or anything else) will fix that.
What we want here is a "gentle gain rider" that will "hold back" louder voices but "open up" for the quieter ones ...and the key to achieving that is actually having our compressor "holding gain" for any voice that's louder than "normal" (as you've noted) with
- A low ratio, being around 1.5 to 1,
- A reasonably fast attack of around 100 to 250 µs,
- A relatively slow release at around 250 to 500ms, being a quarter to half a second or so and
- Its threshold set to the level of our "average" participant, often being in the range -40 to -25 dB.
As with "gain trim", it's often easiest to first set up a "model" or "template" for such compression "at base" or "at home", by listening to and tweaking the above settings on an "average" voice, (very often listening via headphones) until we're reasonably happy with our "automatic level control", ...bearing in mind that the "pumping" of room noise that's often really objectionable when listening to our one "sample" mic will almost certainly be "masked" by other voices during an actual multi-mic session.
(I'll just repeat, however, that it's vital for NO such compression to be enabled until after FBS has been set for a given venue.)
Having now established and enabled all of those settings in our "sample" channel, we then copy and paste them to every one of our participants' channel strips ...and save that set-up as the "starting point" for our gig, with the result that only slight individual adjustments should then be needed during each session.
Happy mixing !