Topic: Mic switches...what do they mean and when to use them?

[manitouman]

Hi y'all! have my gear ready to go but I have a question about the switches on the mics. I have a set of Peluso's CEMC-6 mics. They have two switches:

The first is measuring "dB" and has three positions...0, -10, and -20. I do understand that 0 would probably be louder than -20 but in what situations would you use these settings? Wouldn't the pre take care of this instead of using the mic setting? Under normal recording circumstances would you just leave it at "0"?

The second switch has three settings: 1) L in......2) 75 Hz.....and 3) 150 Hz. Now I have no idea what these mean so some education would be appreciated. When would these be used or would you just let the pre handle this as well?

Here's my gear just in case it makes a difference in the responses: Peluso CEMC-6>silvers>Oade W+mod UA-5>S/pdif>Microtrack

Thanks for the help!!

[DSatz]

mshilarious wrote:

> You use the pad switch if the level is so hot that it clips your preamp, even at its lowest gain setting.  Also, a pad will help prevent overloading the mic's internal circuitry if the level is getting seriously loud (>130dB for many mics).

Umm, the second part of your answer is right, but the pad switch on a condenser microphone generally reduces the sensitivity at the microphone's front end, leaving the noise voltage of the circuit unchanged. Thus if you use the pad when it isn't needed to prevent overload in the microphone, you effectively raise the noise voltage relative to the signal, by the amount of the pad (10 - 20 dB or whatever).

If your preamp's input is clipping but the microphone (itself) can handle the sound pressure levels OK, then use a balanced, resistive, in-line pad at the input of your preamp. These are available inexpensively from Shure, Audio-Technica and other pro audio manufacturers. Such a pad will reduce both the signal and the microphone's intrinsic noise by the same amount at the same time, so the signal-to-noise ratio of the recording isn't spoiled.

--best regards

[TNJazz]

If your preamp's input is clipping but the microphone (itself) can handle the sound pressure levels OK, then use a balanced, resistive, in-line pad at the input of your preamp. These are available inexpensively from Shure, Audio-Technica and other pro audio manufacturers. Such a pad will reduce both the signal and the microphone's intrinsic noise by the same amount at the same time, so the signal-to-noise ratio of the recording isn't spoiled.

Wow, you really do learn something new every day here on Sesame Street.   

Thanks, Oscar!  +T

[manitouman]

Wow, you guys really lost me there. 

No disrespect or anything just a lot of information to absorb after dinner.

So if I'm recording loud rock shows should I leave the mic set at "0 dB" or should I set it at "-10 dB" and bring it back up in post? What is the reason to lower it -10 and then bring it back in post?

As for the other switch, should I just leave it at "L in"? The Peluso's will have the cardioid caps. I have 3 Red Rocks shows that I will be about 10th-15th row from the stage. I also will have 3 Gorge Amphitheater shows where I will be 30th-40th row from the stage. So if I understand the first comment correctly, I shouldn't have to use either th 75 or 150 Hz setting because I want that bit of bass in a concert recording?

Thanks for any help!

[kbergend]

I've recorded about a dozen shows with those mics, and you most likely won't need to use either of the switches at 10+ rows back.  In the very unlikely event you find your mics or preamp clipping with the gain turned all the way down due to VERY high sound pressure levels, then you can use the -10dB pad switch setting to bring down the signal from the mics (I have no idea whether this is better or worse than using a preamp or inline pad).  If the bass where you're set up is EXCEPTIONALLY thumpy or boomy, using the 75Hz rolloff setting will attenuate that.  But in most situations, you'll get better results leaving them at the 0dB and flat positions.

3 shows at Red Rocks -- I'm jealous.  Good luck!

[twatts (pants are so over-rated...)]

So if I'm recording loud rock shows should I leave the mic set at "0 dB" or should I set it at "-10 dB" and bring it back up in post? What is the reason to lower it -10 and then bring it back in post?

Leave it at zero.  Use your preamp to set your levels.  If at the lowest possible setting, your pre-amp is still clipping, use the -10db pad.  Only use the pad if your pre-amp is clipping at its lowest setting.  If you tape really close to a sound source (stack taping or on-stage), you may need the pad.  But in most cases, you won't use it.

You should try to run your rig so you get best possible levels at show.  Don't run your levels so low with the expectation that you can boost them later.  Try to get the best levels at the show while you are there; you'll get better results than if you run low and try to turn it up later.

As for the other switch, should I just leave it at "L in"? The Peluso's will have the cardioid caps. I have 3 Red Rocks shows that I will be about 10th-15th row from the stage. I also will have 3 Gorge Amphitheater shows where I will be 30th-40th row from the stage. So if I understand the first comment correctly, I shouldn't have to use either th 75 or 150 Hz setting because I want that bit of bass in a concert recording?

Thanks for any help!

Don't use the bass roll-off.  As above, unless you are clipping, there is no reason to run this.  If you get home and the bass is too hot, you can roll it off in post-processing.  You will get better results if you have to roll-off excess bass, than if you try to boost a weak bass response because you used your mics roll-off.

At least that's my thinking...

Terry

[DSatz]

manitouman, the most direct advice I can give you is this:

(1) Find out the maximum sound pressure level ("SPL") which your microphones can handle. If the music you're going to record seems likely to exceed that level, then the microphones' pad switch is your very good friend, because it's the only thing that can prevent the mikes from being overloaded, and it will also make life easier on your preamp/mixer/recorder.

(2) The next thing to look at is your preamp/mixer/recorder. mshilarious is right when he says that overload at this stage (the input of whatever equipment your mikes are connected to) is more common than microphone overload itself.

Unfortunately not every manufacturer specifies the maximum signal levels that their preamp inputs can handle. But if they do specify it, or if you can measure it with a signal generator and a meter (which isn't hard), then you can use figure out the maximum SPL at your microphones which your recorder/mixer/preamp input can handle when driven by your microphones. It's a simple calculation which depends on the sensitivity of your microphones (usually specified in mV/Pa).

If that SPL is lower than the maximum SPL of your microphones, and if you think it's likely that you'll ever have to record anything loud enough to overload the mike inputs of your mixer/recorder/preamp now that you know what the limit is, then you need the kind of resistive pads I was talking about. That's because (and here mshilarious is unfortunately mistaken) you don't want to use the switch on the microphone unless the microphone itself is likely to be overloaded by high sound pressure levels (or wind, or other mechanical interference, etc.).

Does that make some sense? We'll help you with the details here if you need help figuring out the dB and voltage limits that I'm talking about.

--best regards

[manitouman]

Thanks for the info! I think I have a handle on this now. And yes I agree that I would rather get the best recording while at the show using the settings than trying to tweak a recording in post. I gotcha!

Thanks Terry for the explanation. I would guess you know the UA-5 fairly well since I believe I'm the 3rd generation owner of one you had a few years back.

Thanks everyone!

[manitouman]

DSatz,

Thanks for the info. Here is what I found at the Peluso site concerning these mics:

Technical Data

Type: Condenser Pressure Gradient w/ 20mm capsule
Frequency Range: 19Hz/25Khz
Polar Pattern: Cardioid w/ removable capsule
Sensitivity: 10mv/pa
Impedance: 200 ohms
SPL: 156 db w/ 20db pad
Equivalent Noise: 14db (A-weighted)
Power Requirements: Phantom - 48v +- 4v
Current Consumption: < 3.0 MA
Size: 22mm x 164mm
Weight: 134 g

So the SPL is listed at 156 dB with the switch set at -20 dB. So without the switch they should be capable of handling 136 dB? Am I understanding this correctly? From information that I found, rock concerts hover around 110-120 dB, so I should be okay at the switch setting of "0".

I'm not sure if this is what you were looking for in the second part of your post but I pulled it from Edirol's specifications regarding the UA-5:

Nominal Input Level (variable)    
Input1/2      -50 to +0 dBu

Input Impedance    
Input1/2       22 k ohm

[DSatz]

Right, we can infer that the maximum SPL is 136 dB. (It's odd that the specs don't say so directly.) But if a concert ever gets that loud, run away if you value your hearing! Anyway it seems as if you should never need to turn that pad switch on, as long as the mikes are being properly powered (since less-than-adequate powering can mean a less-than-specified maximum SPL). That's very nice.

I wasn't able to find detailed specifications on Edirol's Web site for the UA-5, but they say that its inputs are on RCA sockets. If so, it sounds as if these might be consumer grade line-level inputs rather than microphone inputs as such. The 22 kOhm input impedance goes along with that. But then I don't understand how you are powering and connecting your microphones. Is there some other piece of equipment between the microphones and the inputs of the UA-5, such as a preamp?

--best regards

P.S.: mshilarious, the series resistors in a properly made in-line pad will have no real effect on standard phantom powering; they should be well within the allowable tolerance for the 6.8 kOhm feed resistors in the first place. If not, then I wonder what value of series resistors you are using.

The other thing is that the noise contribution of a condenser microphone's capsule naturally has a 1/f characteristic. It may exceed the FET or tube noise up to a few hundred Hertz, but at midrange frequencies and higher, the FET or tube's noise predominates. Now if you look at equal loudness curves at the level of typical microphone self-noise, you see that our ears are some 30 dB less sensitive to noise at the lowest frequencies than noise in the midrange, especially the upper midrange. So in terms of auditory perception, it really is the first active device which determines the noise output of the microphone--not the capsule. Since the usable signal output decreases by the amount of the pad, but the noise level does not, the signal-to-noise ratio decreases by a corresponding amount whenever you use the pad.

You are certainly right that this loss of s/n performance may not matter in every case--and if you have no other option, a little extra hiss is certainly preferable to hard clipping. But built-in pads in microphones should be avoided if there is no real need to use them, and in any situation other than clipping the microphone's own electronics, in-line pads offer an alternative that doesn't fundamentally lower the s/n ratio.

[goodcooker]

I have run my CEMC6s with the pad off (DIN,cardiod from a distance) and the pad on -10db (at Banyan, XY~20 ft back FOB, Stephen Perkins' drums front center stage). At Banyan I did it just to be safe. I was still running +20 on the V3. I don't think using the pad increased the noise floor enough for it to matter at a loud rock show.
I never run the bass rolloff. I did with other mics and was dissatisfied with the results. I would if it was inside and I was right in front of a massive sub.
Try it a few different ways and see what you like.

Remember that the switches on these mics are recessed and can be hard to get to "on the fly".