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Tip Of The Day #40

Tip Of The Day #40: With EQ, remember the phrase – “Subtractive is Attractive.” Boosting adds noise, & decreases Gain Before Feedback.

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My “Bass Player’s Compression Dilemma”

I am a bass player. I play a passive bass (one where the pickups do not require a battery inside the guitar). I love the tone of them – I love the low maintenance aspect of not having to wonder if I accidentally left the guitar plugged in and my battery might be drained.

But I’m not a rich man. I do not own a Lakland, or other high-end bass. My 5-string Yamaha cost me about $450 new several years ago. As such, the low B-string is a little “flabby” sounding – it doesn’t have a real strong fundamental tone down there. In order to correct that issue, I’ve been able to use compression. Compression is generally needed on all bass guitars because the volume tends to jump up and down a lot depending on the note, the fret position and the pickup selection. But with a rather inexpensive 5-string bass with a flabby B string, good compression is an absolutely CRITICAL part of my signal chain. [Here’s a quick video of my playing with the bass so you can hear what it sounds like with compression on the front end]

But now comes the dilemma – part 1: Do I totally depend on the sound guy of whatever venue I’m playing to instinctively know I have Flabby B Syndrome and assume he has the gear and knowledge to fix it? I’m not a fan of that option. How do I know he isn’t using too much or too little compression and completely desroying my dynamic control? No – I’d much rather have control of the compression on stage with me so I can set it correctly, monitor what it is doing, and can actually hear the results live.

Now for the dilemma – part 2: 99% of all stomp-box type compressors STINK for bass. They are noisy. They pump and breathe (an audible, non-pleasing compression side effect). How about the other 1% of them that are decent? They’re EXPENSIVE! Like $185 expensive. No thank you. If I’m going to pay that much for a compressor, then it had better be recording studio grade, baby. Come to think of it – that’s what I’m really looking for anyway – a studio-grade compressor for my bass rig.

So here comes dilemma – part 3: Studio-grade compressors are made for Line Level usage. As in +4 dBm (1.23 volts). These compressors want to see that hot of a signal coming into them. But wait! Instruments – especially passive ones – don’t put out even CLOSE to that amount of signal. Another issue is that of pickup loading. If the bass pickups do not sense the correct high-impedance load connected to them, then they will not output at their maximum capability and will lose some frequency response and level. So directly connecting my bass right into a studio-grade compressor is not really a viable option. There would also be the problem of monitoring. How would I connect my amp? The output of the compressor would be line level – and my amp’s input will be expecting instrument level! ARGH!

But here’s where I found the magic answer. An older dbx 163x compressor was EXACTLY what I was looking for. It has some unique features that fit my purpose wonderfully. First, it has two different inputs – a front and a rear. The rear input is line level and works like most high quality compressor inputs do. But the front input is High Impedance – SPECIFICALLY MADE for instrument level. The unit actually has a little preamp built into this input, so it even loads my pickups correctly! As for output, it has a very easy to adjust output level – so I can send out instrument level to an amp or direct box!

They don’t make these any more, but you can still find them on eBay and such. I was able to purchase two of them for $80! I now have exactly what I was looking for – studio grade compression with on stage control – and it wasn’t expensive!

Understanding Signal Flow

Knowing the audio path through a mixing console is absolutely critical to a sound engineer’s success. Using this information, the engineer can quickly TROUBLESHOOT the likely causes of common problems, and can even narrow down the possibilities of unexpected major problems. It can also prevent mistakes because you know what the audio is doing at each stage of the console.

It also gives the audio tech CONFIDENCE as he sits behind the console. This is because he fully knows the ins and outs (sorry for the pun) of the equipment. Finally, it gives the audio tech a FOUNDATION of understanding which allows them to move from room to room or console to console and not be thrown for a loop. Instead of thinking, “the 2nd red knob on my old console was always set to 12:00, does that mean the 2nd blue knob on this console should be set the same?” The knowledgeable tech will know exactly what that knob is and where it is in the audio signal chain (even consulting the owner’s manual if necessary.)

You want to be an excellent all-around driver of vehicles, not a specialist who only knows and drives a Chevy Malibu 2-door with the small V6.

GENERALITIES:
In general, the controls that you tend to “set” are at the top of the console, meaning you have to actually reach for them. The conrols that need more adjustments along the way are closer to your hands (i.e.: the channel faders.)

The channel strip tends to lay out generally “in order” as it applies to the audio signal flow – Gain, then EQ, then the Fader, for example. But this is a very broad overview. There is much more detail to be learned.

So how do you learn the signal flow of your paticular console? You break out the manual. It will contain what is typically called a “block diagram”. Now block diagrams can be headache-inducing nightmares. Check out this one for a Yamaha DM2000:

So I recommend that you take the time to create your own simplified signal flow. Just follow the lines on the block diagram to determine the signal path. It’s also recommended that you make it in linear, vertical orientation so that it helps you visualize the flow better. You can use any drawing or paint program to make one.

EXAMPLES:
I have created a few Signal Flows for study. They can be extremely valuable learning tools. (Click on the images to see a full sized version). [Note: These images are for personal study only. Not to be used in any other websites or printed materials.]

Here is the signal flow of a Mackie 1604 VLZ.

And here is a larger format Yamaha IM8•40 console.

And here is an APB Dynasonics Spectra-C/56

BASIC DEFINITIONS:

Gain: A level adjustment designed to optimize each signal coming into the console.

Pad: If you turn the gain all the way to the left and the signal is still too hot, then you should engage the pad, which will reduce the incoming signal by a preset amount (usually 20 dB or so).

HPF: High-Pass Filter. A circuit which sharply decreases low frequencies, reducing mike handling noise, stage rumble, and plosives (p-pops).

Polarity: A simple switch which flips the polarity of the input. (Sometimes incorrectly labeled ‘phase’). Useful for eliminating phase-cancellation when using multiple mics on the same source (both the top and bottom of a snare drum, for example).

Insert Loop: A patch point for connecting outboard gear, such as a compressor or effects unit.

Direct Out: An individual channel output after the gain stage, but before EQ or fader involvement. Most often used for feeding multitrack recorders.

Aux mix: A separate mix of each channel which has its own output, which can be used to feed stage monitors, a recording mix, sends to a reverb unit, or other uses.

Pre/Post: An indication of where the Aux mix splits off from the main signal. If it is labeled as as “Pre” or “PreFade” mix, then its level is completely independent of the channel’s fader. If it is labeled as a “Post” or “PostFade” mix, then the aux’s level will also be affected by the channel fader as it is adjusted.

PFL: Pre Fade Listen. Works as a “solo” button for the engineer’s headphones. You can isolate an individual channel, and hear changes you make with the EQ. Because it is pre-fade, it does not matter where the fader is at the time.

Group/Subgroup: A Subgroup (or just “Group” on some consoles), is a tool used to help the audio tech during a service or performance. Rather than have to independently mix 32, 40, or even up to 56 channels on a console, you can assign for example, all the drums to one fader called a “subgroup”. The Subgroup does not affect any aux sends, it only affects the main mix. So I can raise or lower the level of all 8 drum mics on one fader – VERY USEFUL.

VCAs and VCA Groups: A VCA stands for Voltage Controlled Amplifier and is a common way to “automate” certain things on a mixing console. You can assign multiple channels to a VCA (just like a group), but the difference is – NO AUDIO IS PASSED THROUGH A VCA. Instead, the VCA acts exactly like a remote control to channels which are assigned to it. Where it gets really interesting is that channels that are assigned to a VCA Group DO NOT have to share a common audio path AT ALL. (This means you can have the entire band on one VCA fader, even if they all are routed to different mixes and subgroups!)

Something to keep in mind with VCAs that you don’t have to worry about with Groups: a VCA provides the exact same function as adjusting a channel’s fader (including any changes to it’s Post Aux mixes). This is different than a SubGroup, as a sub would only affect the house mix.

Buss: a common term seen in mixing console owner’s manuals. It is an electrical term rather than an audio term. Technically, an aux mix, a subgroup, a master mix, a mono output, a matrix output, etc. are all busses. The only way this term becomes important to an audio tech is in the possibility that you get some “buss distortion) which may not show up on the meters. If, for example, I assign all 32 channels of a console to SubGroup 1, and the console I’m driving doesn’t have Group Meters, and I keep the Group 1 fader low enough that I don’t get overloads on the Master Mix Meters, then it would be possible to overload the Group 1 buss, creating distortion, that would not show up on any meters. This is an extreme example to make a point – but I think you get it.

Matrix Mix: A completely different kind of output available only on the larger consoles. It’s sole purpose os to create an alternate mix to be used for recording, for routing a different mix to a different room, or for any other specialized purpose. You will not see a Matrix split on the following audio signal flows. Why? Because they are not made up of individual channels! A Matrix mix is created solely from mixing the Main Outputs and SubGroup Outputs. So a Matrix Out is created downstream from any individual channel functions.

The Order of Input Channels

There are lots of theories on channel layout. Some board operators prefer vocals first, followed by the band. Some use the opposite scenario, with the band first and then vocals. And some don’t give much thought to the process, just plugging things in order as they come from the stage (Stage Pocket 1, 2, then 3, etc.) regardless of what instrument is represented on that line.

Over the years, I have advised my clients and friends to generally adopt the “Pyramid Mix” channel order. For those of you not familar with the Pyramid Mixing technique, here is a diagram (created by Curt Taipale) which explains the concept:

So how do you build a pyramid? You start with the bottom layer and work your way up. I do modify it slightly, in the sense that I want to keep like instruments together (guitars, keys, drums, etc.). Also, in most settings I’ve worked with in the last several years, guitars are dominant with keys being primarily ambience (organs, pads, etc.) – so the pyramid is slightly modified there. It’s also helpful if you lay out the channel order with regard to your Groups. The typical large format board has 8 subgroups, so I take that into consideration as well. So here is the general layout I recommend to most clients:

01 – Bass Gtr
02 – Kick Drum
03 – Snare Drum
04 – Tom 1
05 – Tom 2
06 – Tom 3
07 – Hi Hat
08 – Crash (OHL)
09 – Ride (OHR)
10 – Percussion 1
11 – Percussion 2
12 –
13 – EG 1
14 – EG2
15 – AG 1
16 – AG 2
17 –
18 – Piano L
19 – Piano R
20 – Synth L
21 – Synth R
22 – Track
23 – Click
24 –
25 – Lead Vox (or Worship Leader)
26 – BGV 1
27 – BGV 2
28 – BGV 3
29 – BGV 4
30 –
31 – Anouncement Mic
32 – Pastor Mic

Notice there are some blank channels in between the groupings. This is for that last-minute request that always seems to come, ie: “Bob is going to be using 2 amps today”, or “I fogot to tell you we’ll need 3 acoustic channels this week”, or “We’re using the Djembe today so we need 3 percussion mics.”

Of course, this order can be scaled up or down depending your exact situation, but now let’s look at the group situation. Here’s a look at the typical 8-group layout:

Group 1 – Bass/Kick
Group 2 – Drums (all drums/percussion except Kick)
Group 3 – Electric Gtrs
Group 4 – Acoustic Gtrs
Group 5 – Keys
Group 6 – Misc (could be brass, choir, lavs, whatever)
Group 7 – Lead Vox
Group 8 – BGVs

You may have to make some modifications if you are running true stereo. Group 1-2 may be Stereo Drums. Group 5-6 may be Stereo Keys, etc.

If you only have 4 groups, it might look like this:

Group 1 – Drums/Bass
Group 2 – Gtrs
Group 3 – Keys
Group 4 – Vocals

I realize this specific layout may not work for everyone, but it has proven to work in many situations I’ve been involved with over the last several years. Whatever layout you choose – it should make sense and should allow you to mix properly without having to go hunt for something.

Tip Of The Day #39

Ask yourself, does this mic really NEED to be wireless? Wired mics sound better and almost NEVER fail.

Tip of The Day #38

Scan the stage and listen for what you see but AREN’T hearing. (via Yamaha Live Sound’s facebook page)

Tip of The Day #37

The Difference Between Tuning & Toning Your Sound System | Bob McCarthy’s Blog: http://is.gd/f4z8I


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