Topic: -10dB pads-- when do you use?

[acidjack]

Just a very basic question, but for some reason my search didn't turn up anything.

I assume that if your mics have -10dB switchable pads, and you are recording loud/amplified music, it is generally advisable to always use the pads, correct, unless you can't get proper levels when doing so?  I may be using some Beyer MC950s shortly and want to be sure I'm right to use the -10dB pad with them.

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There are two occasions when I'd use the pad:

1) When I'm spot micing something (or close enough to be considered spot micing). Essentially, if I had foamies correctly inserted and standing close enough would risk damaging my hearing (130+ db level).

2) My mics were hot outputs (25 mv/pa or higher such as the beyers) *and* my recorder overloads with the signal.

Otherwise I don't use them.

My 722 will accept a mic in signal that is hot, so I never run the pads on the 930s since I'm not spot micing stuff. Jason runs pads somewhere in the chain on occasion (I think, Jason please clarify this if I'm wrong) cause he's had some overloading by the time it gets to the recorder.

Getting distortion at the recorder is more likely then at the cap. For distortion to occur at the cap, you'd have to have the SPL up past safety limits to the point where permenent damage is being done (to your ears) and that is most likely to occur when your spot micing (whether it's full on stack humping or stage production spot micing). OSHA has a chart with comparable stuff if you're interested.

edit: clarified remark, my bad.

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For distortion to occur at the cap, you'd have to have the SPL up past safety limits to the point where permenent damage is being done and that is most likely to occur when your spot micing (whether it's full on stack humping or stage production spot micing). OSHA has a chart with comparable stuff if you're interested.

Not quite, and the OSHA limits apply to ears but not microphones.

Oops, that what i meant but I didn't add the "to your ears" part. My bad, edited my comment above to reflect it.

Using the mic's internal pad will degrade the mic's signal-to-noise ratio, so it should never be used unless on a truly loud source.

I couldn't remember where I'd read that so I didn't add it. Couldn't find different S/N specs when I pull the 930 specs so I figured I wouldn't mention it. It's logical, but I couldn't remember it for the life of me. Thanks.

[stevetoney]

It all depends on what your output levels are.  I generally don't use the pads when I don't have to.  The pads are nice to have though in case your mic sensitivity needs to be scaled back, yes, when the SPL levels are very high.  It's simply another nice variable to have available to you when you need to adjust SPL. 

I'll give you an example of where a mic pad was necessary for me.  The mics were inputting though a battery box (fixed gain).  I was recording with an MTII which doesn't have the hi/low sensitivity settings like the MT2496 has, so levels on the MTII were close to peaking when I had it rolled all the way back to the lowest setting possible.  It would have been great to have a pad there because that would have given me more headroom to keep levels from peaking during the loudest passages.

[newplanet7]

I've run them a few times when running onstage. More for percussion
than anything else.
Didn't notice any ill effects. It just scaled back the signal.

[runonce]

The answer depends on your preamp...distorting the mic itself...is rare in our pursuits.

On-mic pads are handy if you find your preamp peaking - and you are adding little or no gain. Might be best to pad down in that situation.

The downside of mic pads (vs preamp pads) is the on-mic pads change the S/N ratio a bit. (the amount of the pad) - but that noise penalty is certainly preferable to brickwalling/overload

I almost ALWAYS run my -20db pads on my preamp...unless Im running something from the Nak/TEAC family - which have really low output.

[taperj]

My rig needs pads, it's all about output for me really. I have km184's which are unattenuated and have a very hot output, then I have a mixpre which doesn't have mic padding, unless I'm a football field away from a loud show I overload to my Korg MR-1. I use -20dB inline pads just before my pre and run through them 100% of the time unless I'm recording something extremely quiet. If I didn't need the pads, I wouldn't use them, but I don't feel my recordings suffer from having to use them. I do believe running them in line as opposed to on a mic also preserves the SNR(I haven't thought that through thoroughly but I think it stands to reason).

J

[huskerdu]

My rig needs pads, it's all about output for me really. I have km184's which are unattenuated and have a very hot output, then I have a mixpre which doesn't have mic padding, unless I'm a football field away from a loud show I overload to my Korg MR-1. I use -20dB inline pads just before my pre and run through them 100% of the time unless I'm recording something extremely quiet. If I didn't need the pads, I wouldn't use them, but I don't feel my recordings suffer from having to use them. I do believe running them in line as opposed to on a mic also preserves the SNR(I haven't thought that through thoroughly but I think it stands to reason).

J

I use the on-mic pads when using my MixPre, but now that you mention this maybe I should be using inline attenuation?

[acidjack]

Correct me if I am wrong, then, but given that the R-44 has adjustable input gain (which comes in handy from hot sources like SBD feeds), presumably, turning down that same input gain would also replace the function of the on-mic pads, correct?

[dean]

Correct me if I am wrong, then, but given that the R-44 has adjustable input gain (which comes in handy from hot sources like SBD feeds), presumably, turning down that same input gain would also replace the function of the on-mic pads, correct?

Sometimes, yes, but at times the spl can still overpower your mics.

[Patrick]

Correct me if I am wrong, then, but given that the R-44 has adjustable input gain (which comes in handy from hot sources like SBD feeds), presumably, turning down that same input gain would also replace the function of the on-mic pads, correct?

Not quite.  There is a difference between "padding" at the preamp and attenuating the mic's output by -10db at the FET.  Padding the mic's output level will, as mentioned, raise the channel's S/N ratio at the very beginning of the chain.  Cutting the amount of gain that you are adding to the mic's output signal is just a different (in most cases, better) approach.

[Neilyboy]

Good to know about running on stage and using the pad. I am planning on running them on stage for the first time this weekend. I may have to back them down a bit depending on how loud these guys play (first time seeing this band as well)
Neil

[runonce]

Correct me if I am wrong, then, but given that the R-44 has adjustable input gain (which comes in handy from hot sources like SBD feeds), presumably, turning down that same input gain would also replace the function of the on-mic pads, correct?

depends on what that gain pot does...if its like an analog sensitivity, then yes, similar...its when you get that knob all the way down...and your still peaking.

On my mixer...I can have everything all the way "down" and it still passes singal...so a 480 will still be peaking uncomfortably until I engage the mic pad. (which I have to use since my mixer has no pad)

[DSatz]

Yo! People!

The ONLY time to use the pad switch on a microphone is when the microphone ITSELF would be in danger of overload if you didn't. It's nearly impossible to overload the capsule of a condenser microphone with loud sound, but the electronics of a microphone can be overloaded by the signals from its capsule. The pad exists SOLELY to prevent that type of overload, and shouldn't be used for any other reason because it raises the noise floor of the microphone by the same amount (10 dB in this case).

If your microphone is NOT being overloaded but its signals are overloading the input of your preamp, mixer or recorder, then the thing to use is a resistive pad at the input of said preamp, mixer or recorder. Such pads will not raise the noise level of the microphone as using its built-in pad will do.

Get it? (Please?)

[dean]

Yo! People!

The ONLY time to use the pad switch on a microphone is when the microphone ITSELF would be in danger of overload if you didn't. It's nearly impossible to overload the capsule of a condenser microphone with loud sound, but the electronics of a microphone can be overloaded by the signals from its capsule. The pad exists SOLELY to prevent that type of overload, and shouldn't be used for any other reason because it raises the noise floor of the microphone by the same amount (10 dB in this case).

If your microphone is NOT being overloaded but its signals are overloading the input of your preamp, mixer or recorder, then the thing to use is a resistive pad at the input of said preamp, mixer or recorder. Such pads will not raise the noise level of the microphone as using its built-in pad will do.

Get it? (Please?)

Great clarification.  Thanks, David.

Say I'm cheap, though, and don't want to buy attenuators.  Should I use the pads on the 414's?  That is, if the *only* impact is increase in noise floor, and I can live with that, is there no other harm?

[DSatz]

Mr. Brecht (I admire your "Threepenny Opera" greatly, and also the "Life of Galileo"), being cheap is a prime reason to bring a pair of in-line resistive pads along to every recording you make. They are the lowest-cost problem-solvers and trouble-shooting tools for overload/distortion problems. If you have an otherwise good preamp or recorder whose mike inputs are prone to overload, in-line resistive pads can save you from having to buy an expensive, new preamp or recorder.

If you hear distortion in a recording and the meters didn't reach 0 dB, how do you know whether the microphone overloaded, or the input of the preamp or recorder overloaded? Simple: Put in-line pads at the inputs of the recorder. If the distortion goes away, it was the recorder inputs (and you now have the best possible solution in place). If it doesn't, then it was the microphone; throw the -10 dB switch and remove the in-line pads. But also PUT EARPLUGS IN because any sound that can overload a modern condenser microphone is very dangerous to your hearing.

This assumes that the microphones are being correctly powered. Condenser microphones that aren't properly powered will generally have problems with premature overload. It also assumes that wind or other strong air currents aren't a factor; they can overload directional microphones without necessarily being audible in and of themselves, especially if your microphones have output transformers. And an underpowered microphone where there is also wind is a disaster waiting to happen.

--As to your main question, an increase in noise relative to signal is the main ill effect of using a built-in, capacitive pad, but there is often a considerable increase in distortion as well. A report about this was published in the Journal of the AES in 2002 by Drs. Pastillé and Ochmann from Berlin, entitled "The 10 dB switch in condenser microphones." The upshot is that it depends on how the pad is implemented and some other factors such as stray capacitance. The traditional approach, which is to add a fixed capacitance in parallel with that of the capsule, can cause a marked increase in distortion (like tripling or quadrupling it).

Some more recent microphones implement the pad by reducing the polarization voltage to the capsule. This doesn't help the noise any, but it doesn't make the distortion worse, either, so it's a better approach. So far, though, I've seen it used only in certain Neumann microphones--it does complicate the DC converter arrangement a bit.

--best regards

P.S.: On a threaded discussion board such as this, everyone can see all the messages that led up to any given posting. I appreciate your enthusiasm for what I wrote, but it strikes me as a waste of bandwidth to quote an entire message back. Of course if there is a particular phrase or sentence that you want to single out for reply (like if it changed your life) then by all means ...

[taperj]

Yo! People!

The ONLY time to use the pad switch on a microphone is when the microphone ITSELF would be in danger of overload if you didn't. It's nearly impossible to overload the capsule of a condenser microphone with loud sound, but the electronics of a microphone can be overloaded by the signals from its capsule. The pad exists SOLELY to prevent that type of overload, and shouldn't be used for any other reason because it raises the noise floor of the microphone by the same amount (10 dB in this case).

If your microphone is NOT being overloaded but its signals are overloading the input of your preamp, mixer or recorder, then the thing to use is a resistive pad at the input of said preamp, mixer or recorder. Such pads will not raise the noise level of the microphone as using its built-in pad will do.

Get it? (Please?)

Excellent, then my logic was correct that my inlines will not degrade SNR like an on-mic attenuator. Thanks DSatz

[datbrad]

One thing I was told by both Doug Oade and Jim Williams years ago was that the -10 switch on AKG 460s is not a resistive pad, but instead a sensitivity switch. I assume this is why there is no change in the specs from the manufacturer for noise levels and THD on the data sheets that shipped with the 460s, compared to the 480s where there is a defined change in SNR specs when moving the switch on the 480s.

I did some home testing on my 460s back in '98, when the 480s were a new model and I first saw the noise spec changes related to the "pad" switch in that mic's manual, to determine if this was also a factor with the 460s, just not published in the specs.

What I found was no audible change in noise when the recorder levels were matched after moving the -10 switch back and forth. This was simply recording in the living room capturing mostly ambient sounds, allowing any hiss to be clearly audible.

Don't know if any other 460 owners have found this, but since that time I have used the -10db position always on them for over a decade now and not had any audible noise issues. I like the comfort of the increased headroom I always have with the -10db engaged on the 460s, and probably will never go back to "0" on the mic switch. Just my own personal experience, YMMV.........

[newplanet7]

What I found was no audible change in noise when the recorder levels were matched after moving the -10 switch back and forth.

Don't know if any other 460 owners have found this,

Here.

[acidjack]

What I found was no audible change in noise when the recorder levels were matched after moving the -10 switch back and forth.

Don't know if any other 460 owners have found this,

Here.

Anyone know if this is true of the Beyers?  The show I am doing tonight is going to be pretty loud ("punk" band, small venue with very good sound system)... The R-44 has a clip light, but as I've been fortunate enough not to have it kick on, I don't know whether that's sufficient.

To be clear, though, I don't think this show will be nearly loud enough to overload the mics themselves... so should the clip light then be sufficient?

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What I found was no audible change in noise when the recorder levels were matched after moving the -10 switch back and forth.

Don't know if any other 460 owners have found this,

Here.

Anyone know if this is true of the Beyers?  The show I am doing tonight is going to be pretty loud ("punk" band, small venue with very good sound system)... The R-44 has a clip light, but as I've been fortunate enough not to have it kick on, I don't know whether that's sufficient.

To be clear, though, I don't think this show will be nearly loud enough to overload the mics themselves... so should the clip light then be sufficient?

What's your max mic-in value on the r-44 (assuming beyers > r44 without a preamp between them)?

If you don't think it will be enough to overload the mics (and I doubt it would be personally), then the next concern becomes the pre-amps in the box which should have a db rating.

[acidjack]

Correct, running direct into my R-44.  The deck has input sensitivity settings, which I only find myself having to lower generally for SBDs. Sensitivity can go all the way down to -56dB.  The manual says that "when the sensitivity setting is too large and clipping occurs" the lights on the affected channel light up. I have seen this happen when running an SBD feed, and reduced those sensitivity knobs accordingly.

Max Input = +24dB

It sounds like changing the input sensitivity knobs is all I'd need to do, I think.... ?

[page]

Correct, running direct into my R-44.  The deck has input sensitivity settings, which I only find myself having to lower generally for SBDs. Sensitivity can go all the way down to -56dB.  The manual says that "when the sensitivity setting is too large and clipping occurs" the lights on the affected channel light up. I have seen this happen when running an SBD feed, and reduced those sensitivity knobs accordingly.

Max Input = +24dB

It sounds like changing the input sensitivity knobs is all I'd need to do, I think.... ?

I forgot that the R44 didn't publish two specs cause it uses an adjustable sensitivity setting. It should be ok and you adjust the sensitivity knobs some. I remember doing that for my fostex on occasion when I changed mics, I had to change stuff. On the fostex, there was a formula for how far to turn so you could do it before getting into the field. I don't know if there are published specs (I guess -56 and +4 at the other end) but you should be able to figure out how hot to run it before you get out there.

[acidjack]

^^ Thanks.  I was especially fretting about it as I forgot to bring my monitoring headphones with me today and won't be able to check on it between bands... Plus I suppose I have been lucky to have idiot-proof gear in the past with few real "options" that I could screw up!

[dean]

Thanks for the info, Mr. Satz!

Brad, any idea if what's true for the 460's is same for 414's?

[taperj]

A report about this was published in the Journal of the AES in 2002 by Drs. Pastillé and Ochmann from Berlin, entitled "The 10 dB switch in condenser microphones."

Thanks to a taperjoe and a friend of his who is a member of the AES I was able to get a copy of this study and read it cover to cover last night. A good read, lots of math.

I think of the whole study the excerpt that strikes me as explaining exactly what we are trying to get at in this thread is here...

"   If an audio engineer desires distortion-free recordings,
a careful consideration of the microphone circuit dia-
gram is necessary. A good option is to use a microphone
with a high level limit. The development of a micro-
phone amplifier with a maximum input voltage of 5.5 V
by a German manufacturer1 makes the discussion of the
10-dB switch obsolete. In this case a reduction of the
output signal is possible using a passive network.
However, it should be noted that the distortion can be uti-
lized for artistic purposes."

This plainly states that for distortion free recordings, DON'T use your mic pad, use the pad in the amplifier(or something inline), that's what they were made for. If the mic capsule is distorting, use the on-mic pad. Notice the main concern here isn't even noise floor(SNR). It's distortion, which IS a concern, much moreso than SNR according to the study. Thanks to DSatz for pointing me to the study, it was a good read, learned a ton.

Ok and, these guys look like they not only know what they're talking about, they look like some serious party animals, someone invite them to the next show!

[datbrad]

Thanks for the info, Mr. Satz!

Brad, any idea if what's true for the 460's is same for 414's?

You know Dean, I am just not sure even about the truth on the 460s. I am making an assumption that because the spec sheet in the manual for the 480 shows a change in noise specs when the pad switch is moved, and the 460 manual shows no change between 0 and -10, that it's meaningful and not a simple omission by AKG on the 460 manual to show everything. Add to this my purely subjective listening tests, and I think I am correct about the 460s.

I think the old 414 ULS is the same as the 460B ULS, but I am not sure about the 414 XLS. It could be a similar relationship. Am I correct that the 414 ULS has a transformer, and the 414 XLS is transformerless? The transformers could be a factor here, I just don't really know. Guess I did not really answer the question, but I hope this helps add to the discussion.

[dean]

Thanks for the info, Mr. Satz!

Brad, any idea if what's true for the 460's is same for 414's?

You know Dean, I am just not sure even about the truth on the 460s. I am making an assumption that because the spec sheet in the manual for the 480 shows a change in noise specs when the pad switch is moved, and the 460 manual shows no change between 0 and -10, that it's meaningful and not a simple omission by AKG on the 460 manual to show everything. Add to this my purely subjective listening tests, and I think I am correct about the 460s.

I think the old 414 ULS is the same as the 460B ULS, but I am not sure about the 414 XLS. It could be a similar relationship. Am I correct that the 414 ULS has a transformer, and the 414 XLS is transformerless? The transformers could be a factor here, I just don't really know. Guess I did not really answer the question, but I hope this helps add to the discussion.

That helps.  Means I can't make any assumptions very safely.  Thanks!

[acidjack]

FWIW, in case anyone needs the info in the future, I ran the MC950s last night without the pads but did lower the input sensitivity on the R-44 by a couple clicks down from -0.  No distortion whatsoever.  This neither proves nor disproves whether to use the pads in certain situations, but I think the answer would be, "It depends on your equipment."

For the R-44 and other decks where you can adjust input sensitivity, I think the answer seems to be pretty clearly "no."

[taperj]

^^ Thanks acidjack, I was going to ask how it all worked out if you didn't post. Great to hear you came out clean

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Avast! Now post yar samples!!!11!

(I'm considering the 950 caps). 

[it-goes-to-eleven]

Two words: Dinosaur Jr.

Too hot for Schoeps.

[acidjack]

Avast! Now post yar samples!!!11!

(I'm considering the 950 caps). 

Recording is available here: http://www.nyctaper.com/?p=2482

A few caveats that I think make it not the most representative recording...

1. The band didn't soundcheck.  Therefore, the engineer had no time to get the house mix set.  The guitars aren't running through the PA, so the guitar is low in the mix.

2. I also have an SBD feed, but it's mostly vocals

3. It's a punk band and basically a wall of guitars, so a not the type of more dynamic recording that would be a better test of the mics.

I'm running them again in a few days at a show that should be more representative. 

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I'm running them again in a few days at a show that should be more representative.

I look forward to the results, but I suspect I'll buy them anyway as I've reconciled why the frequency response looks the way it does, or at least why I think that will be ok.