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Everyone loves to give advice

And today’s your day – I’m looking for some. The M7 is currently set up to interface with the Aviom via direct outs except where a mix is actually required. For example, the kick and snare channels on the Aviom come off the M7 via direct outs, since there’s no mixing that needs to happen to create those Aviom channels. The BGV channel on the Aviom, however, comes off the M7 as an aux send (or a mix send, in Yamaha speak), since a blending of multiple singers is required to create that Aviom channel.

Sounds great and fine, but something we’ve learned is that the direct out comes off the console pre-on (meaning, pre-channel-on). This means we can’t just mute the electric channel when a guitarist plugs in and prevent the pop in the monitor wedges (i.e., we can only prevent the pop in the house). Or when vocalists enter from off stage and pick up their mics, those seated in the front row may get to hear the rumble in the wedges.

According to the M7 book, you can mute the direct out on a channel if you select the channel and use the centralogic screen. That works fine for muting the guitarist when he needs to plug in, but it doesn’t allow you to rapidly mute the direct outs of multiple channels. This creates a lot of work when Curtis and the vocalists are entering/leaving the stage. You have to mute both the direct out and the channel for each channel, and muting the direct outs can’t be tied to a mute group. You can also combine the muted channels and direct outs into a scene, but that’s hindered by the possibility of, say Marissa praying instead of Curtis after one song (i.e., the scene would have Marissa and the other vocalists muted – both channels and direct outs – and leave Curtis live, but in this case, you’d need Curtis muted and Marissa live). What we really need is a way to mute the Aviom sends post-on (aka post-mute) so that when you mute a channel in the house, you’re also muting its send to the Avioms.

According to the manual, the M7 lets you create aux sends (mix sends) post-on. It’s not clear on how you do it, and it doesn’t mention whether these mixes can be pre-fade, which is what we really want for monitor sends. But assuming we can, I’m thinking we should replace the direct outs for the acoustic, CM’s vocal, and the lead female vocal with mix sends. Assuming stage performers keep their instruments silent, we could leave their direct outs alone (the example of the guitarist plugging in, earlier, can be accommodated by selecting the channel and muting both the channel and the direct out on the centralogic screen).

Does this sound like it would work? Anyone have other ideas? If only we had unlimited money and every performer wore in-ears!

Rob

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March 2, 2009 at 8:53 pm 3 comments

Channel dynamics – Part 2 – Limiters, Expanders, and Gates

OK, peeps – let’s finish up dynamics (at least as much as I’m covering for now). If my last post on compression made sense, then extrapolating limiters, expanders, and gates should be pretty easy. Let’s start with limiters.

A limiter is nothing more than a compressor with an infinite ratio. Any signal level greater than threshold will be reduced to threshold; in effect, limiters govern the maximum amount of signal that can pass through them. Their main purpose is protection of your ears or equipment. If you’ve ever looked at our old Hear Back mixers, you’d notice they have a limiter. So do many iPod-like music players, and they’re often hiding along the output stages of large PA systems. You set the threshold to the maximum level your ears or the equipment can tolerate and that’s the level to which the limiter will limit. And unlike compressors, which may repeatedly compress a signal throughout a song, you rarely want to be engaging a limiter. If you are, you’re probably running something too hot.

Now let’s talk about expanders. These great devices expand dynamic range, but not by making a signal louder, as you might at first expect. They actually expand dynamic range by reducing the amount of signal (by a ratio) once it drops below threshold.

Expander Input/Output Characteristics

Expander Input/Output Characteristics

Make sense? If you can imagine a signal getting progressively quieter (i.e., reading right-to-left in the figure), an expander doesn’t do anything to the signal until it falls below threshold, at which point the expander gets busy and reduces the signal even more rapidly (per the ratio). As with compression, you can often set an attack and release time. The attack time refers to the time it takes the expander to stop expansion once the signal rises above threshold; the release time determines the duration until a falling signal is further decreased by the set ratio. At first, it may seem a little counter-intuitive, but think about it for a few minutes and hopefully it’ll make sense.

Just as a compressor with an infinite (or very high) ratio is called a limiter, an expander with a very high ratio has new name: a noise gate. Gates have numerous applications in live sound. For example, we’ve all run into the problem of audible noise from an instrument during moments of silence. This is usually easily remedied by inserting a gate and increasing threshold just until the gate kicks in when the performer isn’t playing (and, for miked instruments, when the rest of the room is relatively quiet, as well). I start with a fast attack, so the gate lets go as soon as the performer begins playing, and a relatively slow release, so it doesn’t chop off any intentional sustain.

Another gate application I’ve read about (but haven’t actually done, since we’ve had fake drums) is in shaping the kick drum sound. Think of a good kick sound – it has a fast attack followed by a fast decay. A common problem is a slow decay – if you’ve heard such a kick, you’d probably describe it as “muddy,” “flabby,” or “lacking punch.” It’s that long decay tail you’re hearing, and that’s where a gate can help. A fast attack is required to allow the gate to let go quickly when the beater strikes the head, but the important parameter is the release, which lets you shape the decay tail (i.e., a fast release chops off more of the decay tail than a slow release). I’ll try to dig up a picture that illustrates this over the next few days.

One final note about our dbx 166, which contains both compression and expansion in one unit – make sure you’re using only the feature (i.e., compression or expansion) that you want on an instrument. I’ve occasionally seen a gate inserted on a channel to reduce noise, but the compressor functions were also (and I suspect, inadvertently) in effect. It’s not inappropriate, per se, to use both compression and expansion simultaneously, but make sure it’s intentional.

Rob

February 13, 2009 at 6:33 am Leave a comment

You look… mahvelous!

Just a quick note to give props to yesterday’s WAM team. Curtis has been talking about stage presence for a while now, and yesterday I definitely noticed this. I don’t know if you guys really did step it up or it was just b/c I was sitting in a new place, but every one of you on stage looked like you were genuinely engaged in worship! Vocalists were looking out and connecting w/ the audience. Gary had a big ol’ smile going on while he was doing his thing. Guitarists were both really getting into their music. Phil was singing along. It made me smile – way to go, everyone!

Rob

February 9, 2009 at 3:13 pm 1 comment

Channel dynamics – Part 1 – Compression

One of the coolest features of the new M7 has to be the ability to vary the dynamics of each input channel.  We’re all used to having EQ on each channel, but the M7 adds separate compression, expansion, and gating, just to name a few!  Separate compression on every channel – I can’t tell you how excited I am about that (seriously – I’ve whined more than once about only having six compressors at our disposal!).  These are phenomenal tools for correcting a number of common problems we’ve all run into.  But since I’ve seen them used somewhat incorrectly over the years, I’m going to give a quick refresher on their functions.

Compression and expansion get their names from the effects their applications have on the dynamic range of a signal (dynamic range is the difference between the loudest and quietest portions of a signal).  Compressors reduce (or compress) dynamic range, whereas expanders do the opposite (i.e., they expand dynamic range).

In this post, let’s look at compression, since it’s easiest to understand (imo).  If you take a signal whose level is slowly increasing, a compressor leaves the signal alone until it reaches a certain level, called a threshold (the setting of which is configurable by you).  Once the threshold is reached by the input signal, the output is reduced by a ratio (which is also user configurable) – anywhere from around 1.5:1 to 20:1 (or even greater).  For an n:1 ratio, it takes n dB of input signal over the threshold in order to achieve 1 dB of output signal over threshold.  Make sense?  A 10:1 ratio compresses the signal more than a 2:1 ratio.

Compressor Input/Output Characteristics

Compressor Input/Output Characteristics

Now, what happens as the level of the loud signal (which is over threshold) starts to decrease?  As long as the level remains above threshold, the compressor continues doing its thing.  But once the input signal falls below threshold, the compressor lets go, and the output level returns to non-compressed levels.

Simple enough, right?  Well, there are several more parameters worth discussing.  First, attack and release times refer to the speed at which the compressor starts and stops compressing once the signal passes through threshold.  For example, if you specify a 10ms attack time, then once the input signal crosses threshold, 10ms must elapse before the signal is compressed by the selected ratio.  Similarly, for a 100ms release time, it takes 100ms after the input signal drops below threshold for the compressor to stop compression and let the signal pass through, unmodified.

Since compressors work by reducing the output level of a signal after the input crosses threshold, they often include an output gain parameter that lets you boost the signal to recoup that loss.  At first, this may seem like you’re undoing the effect of the compressor, but the output gain boost is applied to the entire input signal, independent of whether it’s being compressed (i.e., independent of whether it has crossed threshold).  You’re still achieving a compressed dynamic range, but the entire signal is boosted; in fact, it behaves much like if you bumped the fader level on the mixer (incidentally, this is why compressed music often sounds louder, and is the source of the nasty “loudness wars” among record companies these days).

Lastly, I’ll mention hard and soft knee, since the M7 allows you to configure this (btw – the dbx 166 we have refers to soft knee as “OverEasy”).  The knee refers to the point in the figure where compression kicks in (i.e., where the signal crosses threshold).  So far, as I’ve described compression (and as is shown in the figure), we’ve been assuming a hard knee.  Soft knee compression causes the compression to take effect more gradually, usually by beginning compression at a very low ratio slightly before threshold and then gradually increasing the ratio up to its set point.  If you “smooth out” the knee in the figure and replace it with a gradual curve, you’ll see the effect of a soft knee.

Now, finally, why do we use compression?  While there are many uses, the two most common ones I’ve had over the years are vocalists and instrumentalists with large dynamic ranges.  Some of our vocalists (in fact, some of our best vocalists) occasionally get really into a song, and they get quite loud.  It may only happen for a few seconds, but when it happens, I wish I could have controlled it so the audience didn’t get blown away for that brief instant (and don’t assume you can “ride the fader” – your brain isn’t as fast as a compressor).  Or I’ve mixed for bass guitarists that start plucking with such fervor that they begin peaking on the console.  In both of these situations, I reach for a compressor.  For vocalists, I like to start with around a 2.5:1 ratio, middle-of-the-road attack and release times, and set the threshold so they are being compressed 6dB or so during their loudest passages.  And then listen – if they’re still blowing you out of the water, try bumping the ratio a bit or dropping the threshold slightly.  For the bass, I like a slightly larger ratio (maybe 4:1), but make sure you set the threshold so that compression only kicks in when they’re really plucking hard, otherwise they’re likely to complain and start turning themselves up even more.  Also, since the bass has a fairly quick attack, I like a faster attack time so the compressor is doing its job before you see red lights on the console.

OK, that’s it for now.  Next week, I’ll build on compression when we get into limiters, expanders, and gates.

Rob

February 6, 2009 at 9:36 am 3 comments

How YOU doin’?

Greetings awesome sound techs!  Today’s post will be some simple introductions, but before I get to that, I just want to wholeheartedly thank you for what you do.  Running sound is tough – a lot tougher than anyone who has never run sound before realizes!  I can think of Sundays over the past few years where each of us has run a mix that was so brilliant – so beautiful to listen to – that it likely made the rest of us envious.  Candidly, as I’m trying to figure out how we can achieve such brilliance every Sunday, I’m struggling to identify what, exactly, makes one Sunday so much stronger than another.  The truth is I don’t know, but I do know that when you hit a strong Sunday, at least one thing is guaranteed – you were giving it your all.  You were part of a team of musicians, vocalists, and fellow techies who were all at the top of their game.  And that’s why, as we move into the new space, I know our potential – we’re capable of greatness, and I’m proud to be part of such a dedicated and talented team.  Thank you!

Now I’d like to introduce you to a couple friends of mine.  The first you may have already met – the Yamaha M7CL digital console we’ll be using in the new space.  Lisa, one of the amazing administrative staff members at newhope, produced some nicely bound hard copies of the M7’s manual for you.  I’ll have copies with me on Sunday – stop by and get yours and dig in!  I read through the first four chapters last night and I gotta say, it’s not nearly as intimidating as you’d imagine from a 282-page owner’s manual!  It actually feels a bit like an analog board, which I like, but with some impressive features I’ve never seen in an analog console!  I’d get into them, but that would spoil the surprise!

Second, meet the Allen and Heath MixWizard WZ3 16:2 (sorry, no hardcopy, but the user guide is available here).  You’ll want to get acquainted with this rather quickly, since it’s the board we’ll be using at Garrett Road until the move, as CPM has extracted nearly all our old gear and moved it to Jarred and Amy Lynn’s spaces in the new building.  It’s quite similar to the GL3300 you and I have grown to love, just with fewer channels and no subgroups, mute groups, or matrices.  In the coming weeks, I’ll be around on Thursdays and Sundays to show you around the new board and offer an extra set of hands during rehearsal.

Rob

January 28, 2009 at 11:58 pm 2 comments


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