My mic keeps making thumping sounds.

I

ironpony

Carbonite Member
I keep trying to figure out what the problem is but cannot. Almost every time I try to record a percussive sound, my mic produces unnatural thumping sounds, that when amplified afterwards, are hard on the ears. The audio is not clipping at all, and this has been happening almost every time I try to record a percussive sound. I am using the AT4053b. It's not wind at all, I don't think. I even tried recording from one side of a wall, as my buddy was banging on the other side. So no wind, since their's a wall in the way that time. And it's not shock since I have a shock mount and am holding it still each time. I'm pretty much holding it the exact same way, as if I were recording any other sound but it's only happening on percussive ones. Any idea what it could be that I am doing wrong? Thanks.
 
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It may be the capsule overloading if the sound pressure level is too much for it, a dynamic mic can be a better choice when recording percussive sounds as it can take a greater SPL.

Capacitor mic's such as the 4053b are very sensitive and sometimes can not take a close up sharp percussive sound but try putting the -10db pad in as that may help.

Also it may be that the mic needs full 48v phantom power to get the full dynamic range and your camera or mixer may be giving it too low a voltage.
 
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Okay thanks, that sounds like the problem. I am using the FR2-LE recorder though, and it gives a lot of phantom power. I have to be careful or it's too much it seems with that. What do you mean by putting the -10db pad in? I could record with another mic but I always fear that it won't match the rest of the room, that scene takes place in, if I switch mics. I can hear a bit of difference, but wonder if they audience will since I'm really picky about those things.
 
You will hear various opinions about mics. Part of it stems from micro budget films tending to do little or no sound post. I'm going to clarify that since folks may go "I do post in FCP!". When I say sound post I mean you have a sound editor, or many, and they are working exclusively on sound in a decent space (quiet, calibrated monitors, treated space - at least to some extent) and they know something about sound post and are not the kid who produced a friends punk revival song and now wants to do film.

If you don't do post then your tracks are basically all production and everything sticks out. To use a painting analogy. If you have an old plaster wall and you paint it all gloss white it will look like sh1t. Every little flaw will stick out like a sore thumb. If instead you do a Jackson Pollock painting over the whole wall you won't see any of those imperfections.

Big films do deep multilayered and complex sound scrapes and no budget films tend to do almost nothing.

IF you are doing the almost nothing sound track then you probably need to use the same mics and record in the same spaces etc or you chance of getting it to fit in is almost zilch.

If you are doing a layered sound track then it's not much of an issue. So on large films recordists use all kinds of mics in all kinds of spaces. There is generally no effort to duplicate any particular location sound. For one thing a big film will create the "location" environment in post so there is nothing to "match". On any given show you will have sounds recorded on everything from large diaphragm studio condensers to total cr@p Radio Shack toss-aways, and everything in between. You are also going to be pulling sounds from the library (the collection of sounds used on other projects that have been cataloged) and sounds off of commercial SFX libraries. Lots of different and unknown mics.

RE: the thump. If your hearing it in speakers it might be a DC offset, or sub sonic sound that is "popping" the speaker. Try slapping a low cut (high pass) filter with the highest Q you can get at about 20Hz and see if it goes away. If it does then you can just process all the files. Sometimes impacts have a huge low end you can't really hear and that will overload the drivers in speakers and headphones.
 
Okay thanks. I know what you mean but I don't have a studio treated environment to make some of the sounds. I have turned a small section of my bedroom into one, and but some sounds I need big spaces to make them, in which is why I have tried to recreate the same sound using similar locations. It's worked out quite well in a lot of cases, as I have asked my fellow filmmakers, and they said they cannot tell the difference. Some of these particular percussive sounds I am having trouble with are also an issue of needing to big of space, than what I have. I have a high pass filter on my recorder but the Q is not adjustable it seems.
 
GaryNattrass said:
It may be the capsule overloading if the sound pressure level is too much for it, a dynamic mic can be a better choice when recording percussive sounds as it can take a greater SPL.

Capacitor mic's such as the 4053b are very sensitive and sometimes can not take a close up sharp percussive sound but try putting the -10db pad in as that may help.

Also it may be that the mic needs full 48v phantom power to get the full dynamic range and your camera or mixer may be giving it too low a voltage.
Click to expand...

If the 'thump' is due to some form mechanical interaction, how would putting a -10 dB pad, in the signal path, do anything, other than attenuate both 'thump' and desired signal...
 
I gave you the wrong impression. The treated space isn't for recording, though that is good, it's for editing and mixing. It really just needs to be non bouncy and fairly dead. If you can really tune it great.

FX recording is almost all done in the wild. You usually go where the sound is. Foley is usually done in a dead studio environment. But that is something that we have also brought into the wild a lot with great results. I was just saying that if your doing a layered sound track don't worry too much about matching mic and location because if it's even in the ballpark it will generally fit in.

I met try running the filter in your DAW. The roll offs on equipment are going to be 80Hz or higher and that may suck more bass out that you want.

Sound is an alternating current (electrically). The lower the frequency the closer it gets to Direct Current. Really low freq. sound has a huge amount of energy but most of it you can't hear. Speakers (headphones are speakers) see the energy and respond to it and that can cause them to overload and make thumping noises. By putting a cut at around 20Hz you are removing the subsonic sounds but leaving the bass.

It may not be your problem but it's easy to check.
 
What kinds of "percussive sounds" are you trying to record? Sensitive condenser microphones, with a few exceptions, aren't often used to record bass drums and such, precisely because they will overload and "thump" when too close to those sources. (Ribbons too, but you don't see those so much these days.) Really heavy duty dynamic mics like the Electro-Voice RE20 or the Shure SM52 tend to be the best for recording percussion in the lower registers.

- Greg
 
Okay thanks I think that's it. Sounds such as banging on walls, landing on floors, etc. Maybe the AT4053b was not the right choice for me, but I'd rather sell it and get a better hyper, rather than get an all new mic for even more money, as I am a little short on money now, since i put it towards other parts of my productions. The thing is I was hoping to get the sounds recorded by this weekend, and those mics you mentioned have to be ordered in. I tried recording the sounds further away but then they sound too far away, compared to the video shot, in which the sound would be much closer up. Anything I can do in the meantime?
 
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ironpony said:
Okay thanks I think that's it. Sounds such as banging on walls, landing on floors, etc. Maybe the AT4053b was not the right choice for me, but I'd rather sell it and get a better hyper, rather than get an all new mic for even more money, as I am a little short on money now, since i put it towards other parts of my productions. The thing is I was hoping to get the sounds recorded by this weekend, and those mics you mentioned have to be ordered in. Anything I can do in the meantime?
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You're not going to like the sticker-shock you'll get when you start to price 'better' hypercardioids than the AT4053b. Yes there are better hypers, but the AT is a perfectly acceptable mic. The 'thumping' you're getting is very probably due to the technique you're using and not to any defciencies in the AT. For starters, move the mic a little farther away from the point of impact and make sure the high-pass filter is engaged on the mic input you're feeding so the lowest frequencies are filtered out. You might double check your shock-mount because it might not be really isolating the mic from the vibrations produced by jumping and landing on the floor or banging the wall as well as you think it is.

What is the exact setup you're using for these recordings - everything about what gear, how it's positioned, and all the other details of exactly what you're doing?
 
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I got an adjustable mic stand, and a homemade shock mount which does a pretty good job. I readjusted the shock mount, and it's doing better. If I put the XLR connection right into the shock mount a little, it helps, rather than having it stick out the back. I just tried the high pass filter, and it seems to help! I hope to get enough good sounds to work with. Is this set up okay, or is there anything else I could. Some of the banging sounds still aren't going as well.
 
All of the above is excellent advice and it is possible that any/all is the culprit (nobody can really tell without analyzing a sound sample).
BUT, one not-so-obvious possibility could be contributing if you are running a 48 volt phantom mike on anything less than that (as noted by Gary N above)...
If you "low-power" a 48v microphone , you can get audible, nasty popping/pumping/buzzing noises; as in, the mike will work, but it will still sound crappy.

GJ
 
hmm that might be it. on the sound recorder though, it does not say exactly how much power is being fed. i just have to guess by ear, and it always seems that 75% is the way to go, as far as mic gain goes. any advice on that?
 
In the meantime you could go to your local music store and pick-up a SM57 or 58 for around $100 cheap, both of which handle high SPL percussive sounds well, or borrow one from a friend in a band or studio.
 
ironpony said:
hmm that might be it. on the sound recorder though, it does not say exactly how much power is being fed. i just have to guess by ear, and it always seems that 75% is the way to go, as far as mic gain goes. any advice on that?
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The gain control setting has nothing to do with the phantom power voltage being fed to the mic. The recorder's specs will say what the voltage of its phantom supply provides and if it is adjustable there will be a switch on the body somewhere or a menu option to select it with. The AT4053b does require a full 48v supply according to AT. That being said, the FR2-LE provides the full 48v according to its specs so you should be fine.

There's more to designing an effective well-isolating, shock mount than meets the eye. It could well be that your DIY solution just isn't up to the job when push comes to shove. The Rycote "lyre system" InVision series is less than about $75 and is arguably one of the best there is.
 
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Another remote possibility is room compression. If the space you're recording in is practically air-tight and you hit a percussive instrument or some such, the walls can act as diaphrams as will any object that is flexible (like the mic's own diaphram). An easy test is to open a door or window slightly to allow reduce the air-compression in the space and try to record your percussive sounds within the room. I can say I've seen/heard this myself.
 
Okay thanks. One of the scenes I am trying to mimic though is actually in a very tigh room that's close off. I have already done most of the others FX for that room, and the sounds that require percussion are the only ones left I am having trouble with. I will see if I can order that shock mount and call some music stores here to see if they have it.
 
j1clark@ucsd.edu said:
If the 'thump' is due to some form mechanical interaction, how would putting a -10 dB pad, in the signal path, do anything, other than attenuate both 'thump' and desired signal...
Click to expand...

The -10db pad on most mics tends to be in circuit inbetween the capsule and the op amp that is inside the mic, therefore putting the pad in will prevent the mic amp from overloading.

It was common on AKG 451 mics when they are used on drum kit hi-hats to put the -10db pad on, it was an add on and physically screwed in-between the capsule module and the rest of the mic body which housed the op amps.

It is rare for a capsule to overload but with high SPL the mic amp comes more into play and can easily overload.

I don't know the AT 4053 but then I googled it the spec clearly says that is has a -10db pad on board: http://www.bhphotovideo.com/c/produ...4053b_Hypercardioid_Condenser_Microphone.html

Lesson: learn your kit and use the options that it has available as they may be the solution to your problems, do people not wonder why they would put a -10db pad on a mic???

This is what is says about this mic in the spec:
Filter and Pad
"A switchable 80Hz high-pass filter and -10dB pad allow you to reduce low-frequency noises and extend the mic's headroom in order to capture loud sound sources"

If that doesn't work then try an SM57 but I suspect the op amp is overloading, it could also be that you are overloading your recorder so check that too!
 
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Okay thanks. I will get an account on soundcloud my old one is not working. I don't think my recorder is overloading as it seems I am giving it the right amount of gain. In some rooms it seems that 55% gain is good and in some it seems that 85% is good. Not sure if I have been doing all correct, but I am going by my ears. My mic did not come with a pad but maybe I should get one.
 
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