1 comment / Posted by Bruce Ohms

PFL: The Sound Tech's Secret Weapon Part 2

In Part 1 of this series we discussed how you can use the PFL system to listen in on different parts of the mix individually. In Part 2 we'll learn how your PFL system can also help you see what is happening too.

PFL and the Meter Bridge: Now Every Channel Has a Great Meter

It can be a challenge to estimate your signal level with nothing more than a channel 'peak LED' indicator. Fortunately, your mixer probably has a master meter bridge that is reassigned to the PFL system when it is active. Setting your channel input gain is a lot faster and easier when you have a multi-segment meter available. You can also observe the output level of your monitor sends and adjust their send level accordingly. The meter bridge even provides a quick method of rechecking your channel gain settings throughout the night in case something has changed. Like the guitar player's master volume? Hey, it happens! This could upset your gain structure or distort the signal but now you can keep a lot better track of the situation. With PFL and the Meter Bridge, you can now monitor and compare channels, groups and sends (even outputs and other parts of the system) as needed in order to get the job done. Put it in the PFL and check the meter.  Find out which channel is overdriven faster than you could by listening.

Let's Put it to Work

Let's say you've got your drum mics sub-mixed in their own group and they're well-balanced, but suddenly they're getting just buried by the bass. Your first instinct might be to go ahead and turn up the drum group fader. But does your system have enough headroom to reproduce the signal? Or are you effectively redlining your PA system? With the PFL off you can see on the meter bridge that the master mix is testing the limits of unity gain, but you can't tell which channels have available headroom. Select the PFL on the group where you've sub mixed your drums. Did the signal level drop (could indicate a technical problem)? If not you'll be able to see how hot the drums are compared to the full mix. The meter bridge shows they're still very loud but other instruments must be competing for the sonic territory. You can easily check each of your channels or groups using the same technique, watching for one instrument that is really hot compared to the others. Armed with this new information you can make better choices about how to balance your mix. In our example, you may find yourself surprised that the bass guitar isn't really that hot compared to the drums. So where is all that bass coming from that's killing your mix? Put on your audio detective hat: "Hmmm, I wonder how much of that bass is really coming from the keyboard patch?"

Be Creative and You'll Find Lots of Great Uses for PFL

Having trouble mixing the vocals because the stage tech got the channels reversed? You don't have to mute them in the mains to check which is which. Troubleshooting a monitor or effects rig that isn't working? Run it back into a muted channel with the PFL selected and verify the signal is reaching the next part of the system (you can even use this 'stethoscope' to check other parts of your PA rig!) Trying to get your drums or backing vocal channels sub-mixed on the fly? Put them in a group so you can listen to them separately without the main mix getting in the way. Working on getting your rhythm instruments to blend well without competing? Put them into the PFL so you can really hear how they sound together and adjust the EQ on each instrument to make it "play well with others." Maybe you're mixing on the fly and once you establish an adequate mix, you'd like to go back through everything and see what you can do to make it really shine.

A great mix is built on a solid foundation. With PFL you can listen to the little details and hear how each part of your mix fits into the bigger picture. You can verify what your ears are telling you by checking the meter bridge. Put the Sound Tech's Secret Weapon to work for you and soon you'll become an audio detective. Sherlock hat not included.

What creative uses have you found for PFL and the Meter Bridge? Tell us in the comments. 


  • Posted On June 03, 2017 by Jason SImonds

    I do a lot of live sound… it would be impossible for me to do the job I need to do without PFL. As your article describes, it allows me to hear what is wrong and work to make it right. Last night it was Sugar Ray and the Bluestones with special guest Sax Gordon, is a big hall with a huge rock maple dance floor. It was critical to get it right. I fought with a lot of boominess… had to separate the guitar and piano acoustically so they weren’t stepping on each other.. of course the sax was easy… floating up there on top of everything.. the harp was also a challenge, getting that boom out but leaving the essence of the sound in.. oh and a marvelous stand up bass…. so yeah… without PFL, I could not do my job to my level of satisfaction… I run a C2448, a C1648p and a older C1644P.. analog is where I am at for many reasons, part of which is the KISS principle.. simple can be better.

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