Audio Popping/ Cracking???

Okay, I've done some extensive testing of one of my HMCs with various sound generators and "real" (concert) sound files (all fed to the HMC as line-level signals).

Tomorrow I'll try to compare the HMC with a DVX or HVX. But for now the findings are:

1) The HMC line input clips at around +10dBu, which is sorta low for pro audio equipment, but not terrible. It doesn't matter what the input gain dials are set to, or what the meters show... you'll hear the nasty distortion whenever the input signal is around +10dBu or higher. I'll test... but IIRC the HVX/DVX had a wider tolerance for input levels.

2) The HMC seems to be a little MORE sensitive to low-frequency sound. Where my external meters show a flat amplitude for a sine wave from 30-10k Hz, the HMC meters start climbing as the frequency drops below ~100Hz, steadily down to 30Hz. Not enough resolution on the HMC meters to be sure quite how "steady" the tilt-up is, but it's certainly there; and the meters become much less stable (read:flickery) at lower frequencies. This could be an artifact of a sampling window for the meter generation that's a lot smaller than the length of a low-frequency wave, but it's strange and not common on other meters I've used.

3) The limiter on the HMC is indeed close to useless. It seems to operate only in a very small range (that is, it only seems capable of reducing levels by 3 or 4dB at most, even with a steadily-high input. It acts as if the attack is too slow and the release too fast, but that observation may be a result of the limited range as well. I'm fairly certain the limiter on the DVX and HVX is MUCH better... and I'd have to assume there's some flaw in the HMC limiter. For all practical purposes, it's useless.

Not knowing the precise gain structure of the HMCs audio system, I can't be certain, but I'd guess it's similarly not the mics but one of the subsequent preamp/converter stages that is causing the problems when using either external mic inputs or the internal mics. Something in there is a little too easily overloaded by strong signals coming in either at mic or line level.

Sad... but likely an easy fix for Panny...

Anyway, as an interim measure... I can't address the internal mics, but an XLR pad or two in your kit may often come in handy for reducing audio levels from mic or line sources before they hit the camera. I'd GUESS that a 10dB pad would be fine for almost any situation, but the switchable 5-10-15 or 10-20-30 dB inline pads will give you the most flexibility...

-Barry
 
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D.R. Gates said:
His mic is a part of the camera.
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I understand everyone's frustration, I have had some footage ruined myself. I guess the point is that there is no single mic that will work for every given situation, especially a built in camera mic that will never fail for recording live bands.

Ullanta brings up some very interesting points. Do you think that this could be a firmware update if your tests prove to be correct, or would this require a hardware update?
 
I'd imagine a hardware fix... but again, we don't know enough about the internals to be sure... perhaps at least the limiter settings are firmware-modifiable?
 
I don't get it guys. I have not been using my camera for "tests" though I appreciate all the hard work people here are putting in to this issue. Except, as I mentioned in 40 some hours of shooting in a variety of audio conditions it has not happened to me. I use good mics, I always carry a set of line pads (Shure switchable attenuators) for hot feeds and never use the on board mics. Always keep levels in a respectable level for digital recording. No pops. Last night over a beer I went through some of my footage where based on what has been posted, I could have the problem. No problem.
 
I understand how this COULD be happening.
I just feel that no other camera system POPS under the same conditions.

I usually shoot with more than one camera, and the second camera (HFS100) does not do this.
 
BrianMurphy said:
I don't get it guys. I have not been using my camera for "tests" though I appreciate all the hard work people here are putting in to this issue. Except, as I mentioned in 40 some hours of shooting in a variety of audio conditions it has not happened to me. I use good mics, I always carry a set of line pads (Shure switchable attenuators) for hot feeds and never use the on board mics. Always keep levels in a respectable level for digital recording. No pops. Last night over a beer I went through some of my footage where based on what has been posted, I could have the problem. No problem.
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OK my first real gig with the HMC is not until middle of may so right now it's just swapping out my SD gear to full HD, one by one.. and testing gear and getting the workflow down. Using the same audio package as I used with the dvx, I've never experienced this kind of pop... So it very well could have beeen a change in design of the audio component, but it sure wasn't a change for the better at least not according to the majority of this thread!
 
BrianMurphy said:
I don't get it guys. I have not been using my camera for "tests" though I appreciate all the hard work people here are putting in to this issue. Except, as I mentioned in 40 some hours of shooting in a variety of audio conditions it has not happened to me. I use good mics, I always carry a set of line pads (Shure switchable attenuators) for hot feeds and never use the on board mics. Always keep levels in a respectable level for digital recording. No pops. Last night over a beer I went through some of my footage where based on what has been posted, I could have the problem. No problem.
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Well...There you have it!

What kind of "good mics" do you use?
 
BrianMurphy said:
I don't get it guys. I have not been using my camera for "tests" though I appreciate all the hard work people here are putting in to this issue. Except, as I mentioned in 40 some hours of shooting in a variety of audio conditions it has not happened to me. I use good mics, I always carry a set of line pads (Shure switchable attenuators) for hot feeds and never use the on board mics. Always keep levels in a respectable level for digital recording. No pops. Last night over a beer I went through some of my footage where based on what has been posted, I could have the problem. No problem.
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If your mic setup isn't in general too "hot" for the HMC to handle, you'll never see this problem. If you use a mixer properly calibrated to the HMC, you'll never see the problem. If you work with board feeds that aren't too hot, or pad the ones that are, you'll never see this problem. So... since it sounds like you're covered on all those bases, you're not hearing a problem.

I mean, really, in my experience at least, it's not a "problem." Every piece of audio gear has a range in which it works, and you have to adjust and calibrate for it. It just seems that the range on the HMC is different from what some people expect, and that the match between its own built-in microphones and gain stages may be less than ideal.... but good audio practices certainly can deal with the issue when using external equipment. Not much one can do using the internal mics in an extremely loud situation... but again, every mic/preamp combo has some limit before distortion sets in. A $20 investment in a couple of low-end dynamic mics will probably yield better results than the built-in mics in high-spl situations...
 
I keep hearing people say things like, "the on camera mic is a low quality mic so no wonder you're having problems with it" or saying that the board or levels are not properly set up.

As if we having the issues don't know how a board feed or levels should be set, or as if we don't know that an on camera mic is an extremely low quality mic.

I think that's somewhat missing the point. I've recorded many concerts with many different camera. Canons, sonys pannys. Xl2, pd150, dvx100, etc. None of those camera with their poor on camera mics had this problem. The audio might not of sounded that great, but the cracking popping problem did not occur.

I wouldn't think that a dvx100 on camera mic would be any way superior to the hmc's. or atleast it shouldn't be. I don't know why it occurs with one but not the other? That's the issue. I could be missing something though. Anybody heard anything back from Panasonic?
 
"Better" is a relative term. I have no data to support this, but the HMC might just be biased to sound better when sound levels are relatively low, at the cost of not handling the ultra-loud sounds as well. Remember, the HMC records only compressed audio... perhaps an emphasis on reducing noise at the quiet end of the spectrum yields a great benefit in compression quality.

Or, maybe it's just a flaw in the audio electronics.

But we can't make general comparisons of "better than a DVX" or "worse than a DVX" unless we look at a few more factors. An SM57 is not "better" or "worse" than a U87 until you place them both in front of a loud guitar cabinet, or an intimate-voice singer.
 
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It's a great camera. Take off the handcuffs. What worries you that we haven't at least suggested a solution for?
 
MattRobertson said:
I wanna like this camera, I really really want to, but its problems like this that have me handcuffed
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Dude, I felt the exact same way. The audio issues scared me off. So I went back to looking at all the other cams in the same price range, but I really didn't like them any better. So I figured I'd just take the chance and get the 150.

I had none of the audio problems with my first wedding shoot last weekend. I reduced the levels accordingly (which you should be doing anyway), and so far all is good.
 
Please keep in mind that the reported problems are in pretty extreme situations. Not to dismiss anyone's claims that the HMC doesn't handle such extreme situations as well as other cams, but for most uses the issues will not arise. Again, if you're investing $3500 in a camera, and likely another thousand in support equipment, etc., a small investment in audio equipment that will totally negate these issues should not be your deciding factor. I mean it literally when I say that for extremely loud circumstances, $20 worth of cheapo dynamic mics plugged into the HMC will likely yield a better result than the built-in mics on ANY cam.
 
ullanta said:
Please keep in mind that the reported problems are in pretty extreme situations. Not to dismiss anyone's claims that the HMC doesn't handle such extreme situations as well as other cams, but for most uses the issues will not arise. Again, if you're investing $3500 in a camera, and likely another thousand in support equipment, etc., a small investment in audio equipment that will totally negate these issues should not be your deciding factor. I mean it literally when I say that for extremely loud circumstances, $20 worth of cheapo dynamic mics plugged into the HMC will likely yield a better result than the built-in mics on ANY cam.
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Can you recommend some cheap dynamic mics that you've had good experience with?
 
Ah, put me on the spot! I don't know off-hand, but I'm generally referring to the kind of mics given away free at Guitar Center promos, or included in cheap kits (somehow I'm imagining Samson-branded) that have 2 or 3 mics, stands, and cables, etc. SM58 knockoffs.

If you want to go a step higher in quality and reliability, an actual SM57 (or even the PG57) is always a good choice....

Mind you, this is for "better than the built-in mics in loud situations". I'm not suggesting these as the be-all and end-all of micing!
 
Well my last post to this thread which is evolving into a kitchen table chat. If you want a handycam ...buy one.
This camera is a fine camera and it records images and sound perfectly. There have been some excellent points and information in the thread. Barry's test kinda says it all...as usual for Mr. Green. Maybe a sticky would be good on this one.
Rant:
I am a professional, I use the best equipment I can afford and still make a living with for my work. Cheap mics are not part of that equation nor are cheap filters in front of my lens. Though I shoot for a living, my kit contains excellent audio gear that has been with me through three camera changes and some pieces longer than that. So buy good gear and it lasts. When I am in a situation that is audio intensive I do what most pros do. I engage and audio person.
If you are doing this for fun or a hobby I am happy you can spend close to 4k on a camera so a few more bucks on good audio gear shouldn't be a problem.
There is an audio forum here full of pros who can answer pretty well any question and if not there then google Ty Ford and pick up a couple of his tutorials.
End of rant.
 
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ullanta said:
Please keep in mind that the reported problems are in pretty extreme situations. Not to dismiss anyone's claims that the HMC doesn't handle such extreme situations as well as other cams, but for most uses the issues will not arise. Again, if you're investing $3500 in a camera, and likely another thousand in support equipment, etc., a small investment in audio equipment that will totally negate these issues should not be your deciding factor. I mean it literally when I say that for extremely loud circumstances, $20 worth of cheapo dynamic mics plugged into the HMC will likely yield a better result than the built-in mics on ANY cam.
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Well the nature of things I record does have me worried :(

I film sports mostly, as well as rap concerts (very loud), events, etc. However there are some instances where I do more artistic, controlled things, as well as music videos, but the lot of my stuff is done in pretty loud environments. I'm tempted to get the hmc, pick up a zoom h4 or something, and get a nice xlr mic. But then that brings up even more issues. Problems with synching audio, mounting the h4, bringing along extra batteries for that, etc. I just wish panasonic wouldn't have skimped on the audio on this unit.
 
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