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Author Topic: Mic sensitivity vs gain  (Read 4495 times)

Kevin Maxwell

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Re: Mic sensitivity vs gain
« Reply #40 on: January 21, 2018, 11:27:00 pm »

It is getting late for me tonight where I live, USA east coast near NYC. If I have some time tomorrow I will write what may be another novelette this time about how I get the best gain before feedback on Lavs. It actually works on any vocal mics. But part of it involves using Smaart. Or at least that is the easiest way to do it. I can try to explain how to do it without Smaart.

Some of this I have posted before so I am copying, editing a little bit and pasting it here. There will be some parts that seem to be repeated when talking about a slightly different EQing method.

One trick to getting a good amount of gain before feedback with lavs or actually any mics is in how you setup the sound system. I like to get the main left and right (L/R) speakers far enough away from the stage towards the audience. Far enough out that the mics arenít too close to them will help a lot. And if there are also delay speakers you donít need the front L/R to be too loud to reach the back of the room. You will usually need to have Front Fill (FF) speakers to cover the area lost due to the placement of the L/R. This all give you better coverage and more control then just L/R speakers.

I used to do a lot of corporate conferences and when we had breakout rooms with ceiling speakers and presenters with Lavs on, one of the tricks was to tape over the ceiling speakers over the stage. I even had in the traveling kit some covers I would use over these speakers. It was pieces of magnetic vinyl sign material cut into circles. This is the stuff that they make the removable signs that you can put on a truck of van. If the speaker covers were made of a material that these would stick to we could cover them and then just pop them off when we were done.     

The other is the trick I use when setting this kind of thing up. I EQ the system for linearity, what goes in is what comes out. Then I insert a good quality EQ in a subgroup of like mics. So all MKE2 mics get the same inserted EQ. And the way that I EQ them is a put one out in front of the speakers (or just a little bit in front of where the mic would usually be used) using it as a measurement mic into SMAART and I EQ it for gain before feedback. The routing is pink noise into the console and into the SMAART input and then take a per-fader send from the board routing the MKE2 on the wireless to your other input on your measurement system. I play pink noise thru the system and take out the problem frequencies. I usually find I also need to pull down around 200hz to have good gain before feedback. Sometimes when I am all done and I check how it sounds if I am not happy I have to do it all over again. But that isnít usually much of a problem because this method is so quick. I seem to get the best results when EQing if I start with the lower frequencies and work my way up to the higher ones. I also only cut frequencies I never boost.   

What works for me may not work for others but if you have the time to tune and test you might find it works for you also.

One other little trick that someone showed me a while ago. When using a lav for reinforcement on a male always try to put the lav on their tie. You want it centered to minimize the movement created distance changes when they move their head. Also have the person look down almost touching their chin to their chest and move the mic slowly up the tie, have them tell you when they can no longer see the mic. You then put the mic at the position it was just before they couldnít see it anymore. Then be sure to dress the cable very neatly, I would usually put a piece of gaffers tape on the back of the tie to keep the wire and mic in place. And for some reason this doesnít apply to women, I find with them I can clip a mic right up at their neck just under their chin and it works just fine.

So to do (EQ) this by ear - I would usually play a bunch of different tacks from different CDs that I am very familiar with the way they sound. What you are trying to do here is to get the system to accurately reproduce the way the CD sounds. While playing the CD I then would listen for the things that donít sound quite right. I like to only cut frequencies when doing system EQing. To pinpoint the offending frequency sometimes it helps to boost the suspected offending frequency when hunting for the right one. So boosting the frequencies to make the bad sound stick out more. Sometimes you find that it isnít the one you thought and you need to try another one. This means bring up the control of that frequency and if itís not the right one bring it back down, when you find the frequency you are looking for you would then cut that frequency, how much depends on what it sounds like. I like to be conservative but you can get the feel rather quickly as to how much of a cut to make. When you are all done using this method you should hopefully find that you havenít hacked the EQ to death. Also try hitting the bypass switch to see the difference with the EQ in or out of the system. It may be a very minimal difference.

I then insert (on the vocal subgroup) an EQ and EQ that subgroup for gain before feedback. The way I do that by ear is to have a vocal mic on stage that is on thru the system (thru the vocal subgroup) and I put another mic into another channel thru the vocal subgroup back at the mixer. I then, while using my voice at a decent level, slowly bring up the mic on stage till it starts to slightly ring (while I am making various noises and talking) I then find that frequency and cut it a bit and continue this till I start to get multiple frequencies ringing at the same time. This is usually the point at which you canít get any farther without hacking the EQ to death and screwing up the sound. All this while I am paying attention to how my voice sounds. This is to give your vocal mics the best GBF (Gain Before Feedback) that you can reasonably expect. If you do this without exciting the system with your voice you will be surprised at the frequencies that pop up when a person gets on stage and talks into the mic. I find most micíed instruments donít usually have a problem with gain before feedback and playback (CD) and instruments donít need the additional EQ that the vocals do.  When more EQs are available you can breakup what needs to be EQed for GBF and do them separately (or in subgroups).  If you try to do a best gain before feedback EQ on the whole system you take the life out of playback and a lot of instruments. Now of course this is assuming you have that kind of flexibility to the system.

(For church)
If you were doing the church system using lavaliere mics on the preacher/speaker and handheld or in stand mics like the SM58 for the singers, I would route each of these types of mics to its own sub group. In other words you would have a wireless lav sub group and a SM58 sub group, and the other instruments in whatever sub groups you have leftover. It depends on how many sub groups that you have. I then EQ each vocal sub group separately. Then the channel EQ on the mixer can be used for tonal shaping for each mic.

(for theater)
If you were doing the traditional theater system using mics on the apron of the stage (apron mics) and mics hanging over the stage (overhead mic) I would route each of these types of mics to its own sub group. The Apron and Overhead mics arenít for picking up individuals they are for chorus number when you have a lot of people on stage and a bunch of them arenít wearing mics. In other words you would have a wireless sub group, an apron sub group, an electrics (overheads) sub group etc.. It depends on how many sub groups that you have. I then EQ each sub group separately. Then the channel EQ on the mixer can be used for tonal shaping for each actor.


I find that when I EQ a system with SMAART I can do it quicker than I can with just my ears and I think I get a more consistent sound.

In my opinion pink noise with an RTA is useless no matter how flat you might think it is. Years ago before Smaart existed I used to use an RTA and I never used pick noise with it. When I had one to use I used it to confirm or tell me what frequency I was hearing by seeing it react on the RTA. And using the techniques I wrote above.

With a program like Smaart there is a learning curve so it isnít a quick program to learn. But with Smaart you compare what you are feeding to the system (pink noise is good for that) and what you are getting on your measurement mic or mics. And what you are going for is linearity, what goes in is what comes out. At least that is how I do it. I have been using Smaart since Version 2 and have been paying for upgrades all along. It is now up to version I am not an expert in Smaart but it have helped me a lot I just recently got into using multiple mic at the same time for the measurements.

I know this is long but I hope there is something in here that will have helped someone.

brian maddox

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Re: Mic sensitivity vs gain
« Reply #41 on: January 22, 2018, 10:41:55 am »

Bisquit = Xanax bar to deal with the frustration.

A nice cup of tea = large rum-bearing beverage to celebrate with.


brian maddox

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       ....for you are crunchy, and taste good with ketchup...'
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