Topic: Mic pad or attenuator?

[thunderbolt]

Ran my Oktava MK-012s (Joly mod) into a Marantz PMD661 (Oade concert) for the second time at WSP on Sunday night and it brickwalled.  Knew it was likely (-18 dB "attenuation" which I know = 0, recording level at 4.5).  These mics are extremely hot, and coupled with the loud show, it was too much.  Didn't bring my -10dB Oktava pads at the time; wish I had, at least to try.

Question:  From what I have read, most don't think highly of using the -10dB pads that come with cheap mics like the Oktavas, because they may degrade sound quality.  Anyone ever used this mic with the pad?  As an alternative, I thought I would try this inline pad:

http://www.amazon.com/Rapco-Horizon-PADBLOX-20-Compact-Signal/dp/B003MLBEQS/ref=wl_itt_dp_o?ie=UTF8&coliid=IWDJYCZ8WWTPJ&colid=30V22QOW0ARSI

One TS member stated he used it with his Neumanns for 200 shows and that it worked well.  Theoretically, would this be less likely to color the sound than the Oktava mic pad?  Is there a better inline attenuator to try?

Ironically, the AT853U "mini shotgun">BB>M10 combo worked great and made a very serviceable tape of the show.

TIA.

[page]

If you are concerned about noise, then attenuators in front of the equipment that will overload over pads just behind the equipment that is producing too hot of a signal.

What's the Joly mod do for the mv/pa output (stock mics appear to be 10mv/pa)? I'm not familiar with it.

[thunderbolt]

Thanks for the reply.  Sounds like an inline attenuator would be better than a mic pad.

AFAIK, the Joly mod does not affect the mv/pa output.

[page]

Thanks for the reply.  Sounds like an inline attenuator would be better than a mic pad.

AFAIK, the Joly mod does not affect the mv/pa output.

Then I'm sort of shakey on why you need any pad.

10 mv/pa with a max SPL of 130db = a max output of -2dbu
The 661 stock has a max mic input of 1.2mVrms which = aproximately +4dbu.

So, with the mic gain all the way down, you shouldn't have brickwalled or clipped. I'm not familiar with the 661 outside of the spec sheet. Does it have an input sensitivity setting of some sort?

[thunderbolt]

Hey Page,

Bear in mind that I'm rather new to digital recording.

I used the mics with the 661 at the "-18 db" attenuation level on the Marantz (which is actually, as I understand it, "0" attenuation).  The concert was very loud and I was FOB.  I was hitting -12dB peaks with the 661 volume control at about 4.5.  The meter showed little in the way of dynamics; the levels just sort of hovered around the -12dB mark.  When I played it, particularly the beginning of the second set, I heard what I think is the result of brickwalling.  (I haven't downloaded it on to my PC yet to look at the waveform.)  What I heard was sort of a flanging/phasey quality, particularly with the bass, very muddy, some distortion. 

Several weeks earlier I taped a jazz show which required me to use -18dB attenuation on the Marantz and a record level of about 5.5.  This leads me to the conclusion that the mics run hot and in the WSP show, overloaded the analog stage of the mic preamp on the Marantz.  An attenuator (or a mic pad) would make sense, wouldn't it?  It would essentially eliminate the possibility of brickwalling by attenuating a hot mic.  At least that's how I understand it from searches here.

[page]

Hey Page,

Bear in mind that I'm rather new to digital recording.

No worries, we'll get to the bottom of it.

I used the mics with the 661 at the "-18 db" attenuation level on the Marantz (which is actually, as I understand it, "0" attenuation).  The concert was very loud and I was FOB.  I was hitting -12dB peaks with the 661 volume control at about 4.5.  The meter showed little in the way of dynamics; the levels just sort of hovered around the -12dB mark.  When I played it, particularly the beginning of the second set, I heard what I think is the result of brickwalling.  (I haven't downloaded it on to my PC yet to look at the waveform.)  What I heard was sort of a flanging/phasey quality, particularly with the bass, very muddy, some distortion. 

Several weeks earlier I taped a jazz show which required me to use -18dB attenuation on the Marantz and a record level of about 5.5.  This leads me to the conclusion that the mics run hot and in the WSP show, overloaded the analog stage of the mic preamp on the Marantz.  An attenuator (or a mic pad) would make sense, wouldn't it?  It would essentially eliminate the possibility of brickwalling by attenuating a hot mic.  At least that's how I understand it from searches here.

I'm not real familiar with the equipment other then the stats, but it seems like something is off. You should be in the clear since (at least I don't think) 10 mv/pa is all that hot (neumanns/schoeps are typically 14 mv/pa, AKGs and my beyers are upwards of 30-35 mv/pa), especially with what many consider a pro machine (the 661). Might ask in the 661 thread if there is something about how you have the attenuator set, thats my best guess.

[SmokinJoe]

The Oktava pad goes between the mic body and capsule, right?  If so, then that is a lot different than putting attenuators between the the mics and the recorder.

The pad keeps the capsule from overloading the electronics inside the body of the mic.  The inline attenuator keeps the mic from overloading the electronics inside your recorder.

According to Page's math you shouldn't need the inline attenuators before the recorder.  I would definitely try the pads next time.  Go without them for the opening act, and use them for the main act and see what happens.

In general,  things to consider:
- the average guy in a forum who says stuff like "octava pads suck" doesn't know WTF he is talking about.  Even if he does know what he is talking about, it may not apply to your situation. (Edit: DSatz is definitely NOT the average guy!)
- recording an acoustic guitar in a sound controlled studio is a really quiet place.  Adding pads would probably mean adding some hiss.  So that guy is correct there.
- A WSP show is a really loud place.  There is a lot of other noise from nearby fans and stuff to, besides the music.  Any tiny bit of hiss that comes from the mics is at least 60db lower that the screaming wookie next to you.  Octava's with pads should have less inherent noise than the AT > M10 rig.

[DigiGal]

I got rid of my Busman BSC1's because their output was too hot for 661 with loud shows.  The current version BSC1's do not have attenuation switches. 

If you went with XLR type inline attenuator pads they would need to pass phantom power on to the mics.

Here is info on the Octava pad from a quick search...
http://www.zenproaudio.com/oktavamk-012-10dbpadb.aspx

[hi and lo]

The oktava -10dB pad is probably the best option to try first. Pads that go between the capsule and microphone body work well because they reduce the polarization voltage seen at the capsules, thus reducing output sensitivity. Self-noise is increased some, but is probably less than an attenuator would add.

[newplanet7]

This is all still very weird IMO.
Mr. Sobel runs his HOT beyers directly in to his oade 661.
A lot hotter than the Oktavas. It must be the mics overloading?

[thunderbolt]

OK, I think I figured out what happened.  The first set (which I didn't listen to first)  sounds OK.  There is no brickwalling, the levels peak about -10, sounds good (though frankly, I prefer the mini-shotguns.  Perhaps I'm just more used to that sound from my old taping days with the Nak 300 guns.)  When I started the second set, I'm very embarrassed to say, I may not have engaged the phantom switch.  The recording sounds fainter, though clear, except that it sounds as though someone is banging a large tympani drum out of rhythm.  I'm guessing that that's simply the mic diaphragm freakin' out from no power.

I will experiment with the 10dB pad, as supplied, and as suggested.  I'm guessing that it's going to give me just the extra bit I may need to have more breathing room and to record a bit "hotter."

You guys are really great, very generous with your time and comments.  I have to say that the level of technical expertise you all have is impressive, and the gear that's being used now would have been unimaginable when I started taping in the late 80s.  Thanks for not making me feel like a moron.

[page]

This is all still very weird IMO.
Mr. Sobel runs his HOT beyers directly in to his oade 661.
A lot hotter than the Oktavas.

That was the exact first thing that came to my mind. Even with the -15db pad on the bodies, that is still approximately 8 mv/pa after pad.

Either the published specs for the 661 are wrong/crap or there is a setting that is misunderstood. What's strange to me is now we have another reported incident where mics in the same mv/pa ballpark (the BSCS-1s) also overloading.   

Mathematically it just doesn't make sense to me.

It must be the mics overloading?

The problem with presuming that the mics are overloading is that 130db would be the constant and I just don't see that occurring at a steady rate...

[DSatz]

hi and lo, the type of pad shown in the picture is actually a fixed capacitor which parallels the capsule. It is precisely the kind to avoid using unless absolutely necessary (i.e. when the microphone's own electronics are being overloaded by the output from the capsule at extremely high sound pressure levels). An in-line resistive pad at the input of (whatever's being overloaded) is preferable, because that reduces noise and signal in equal amounts. Capacitive pads, on the other hand, reduce the signal while leaving the noise level unchanged, thus lowering the overall signal-to-noise ratio. They are also somewhat prone to raising the distortion level of the microphone.

If in fact this were a device to reduce the capsule polarization voltage it would be preferable, but that approach isn't widely used yet.

--best regards

[hi and lo]

+t dsatz for catching that! I tend to forget that not everyone does things like schoeps or neumann!

[JasonSobel]

This is all still very weird IMO.
Mr. Sobel runs his HOT beyers directly in to his oade 661.
A lot hotter than the Oktavas.

That was the exact first thing that came to my mind. Even with the -15db pad on the bodies, that is still approximately 8 mv/pa after pad.

Either the published specs for the 661 are wrong/crap or there is a setting that is misunderstood. What's strange to me is now we have another reported incident where mics in the same mv/pa ballpark (the BSCS-1s) also overloading.   

Mathematically it just doesn't make sense to me.

It must be the mics overloading?

The problem with presuming that the mics are overloading is that 130db would be the constant and I just don't see that occurring at a steady rate...

right, my guess is that the problem is with the mics somehow overloading.
If you need to set the level knob on the PMD-661 to ~4.5 or below in order to not get digital clipping, you run the risk of overloading (brickwalling) the pre-amp.  My first time out with the beyerdynamic CK930's and the PMD-661, I did just that.  I didn't have the -15dB switch turned on on my mics.  It wasn't constant throughout the music, but all the loud peaks brickwalled the pre-amp.  Since then, I've just left the -15dB pad on my mics engaged, and I haven't had the problem since.

but even though you had the level meter at 4.5, I don't think you were brickwalling the pre-amp.  the originally poster said:

I was hitting -12dB peaks with the 661 volume control at about 4.5

With peaks at -12dBfs, that means that you didn't need to run the PMD-661 at 4.5, you could have raised the knob and peaked higher.  With the level meter at 4.5, only very loud peak are going to brickwall the pre-amp.  but your peaks are at -12dBfs, which shouldn't be enough to overload the pre-amp, even with the level knob at 4.5.

All this leads me to believe that it was an issue with the mics.

OK, I think I figured out what happened.  The first set (which I didn't listen to first)  sounds OK.  There is no brickwalling, the levels peak about -10, sounds good (though frankly, I prefer the mini-shotguns.  Perhaps I'm just more used to that sound from my old taping days with the Nak 300 guns.)  When I started the second set, I'm very embarrassed to say, I may not have engaged the phantom switch.  The recording sounds fainter, though clear, except that it sounds as though someone is banging a large tympani drum out of rhythm.  I'm guessing that that's simply the mic diaphragm freakin' out from no power.

I will experiment with the 10dB pad, as supplied, and as suggested.  I'm guessing that it's going to give me just the extra bit I may need to have more breathing room and to record a bit "hotter."

You guys are really great, very generous with your time and comments.  I have to say that the level of technical expertise you all have is impressive, and the gear that's being used now would have been unimaginable when I started taping in the late 80s.  Thanks for not making me feel like a moron.

I don't think that is the problem.  Your mics need phantom power to work.  If you didn't turn on phantom power, you would have noticed it right away.  your levels would not peak anywhere near -12dBfs if phantom power was not turned on.  basically, you wouldn't get anything that is recognizable as music, if you didn't have phantom power turned on.  I still think the problem was something with the mics being overloaded, but I don't think it was caused by a lack of phantom power.