Audio is Really Quiet

D

doofalot

Active member
I filmed some green screen stuff with the canon XHA1 and an external microphone (i believe the oktava mk012) and i had both channels up to full and the microphone really close to the subject.

Still, when sampling the audio, it was pretty quiet and the signal to noise ratio wasn't all that high.

Is there more I could be doing with my camera settings, or in Final Cut, or am I missing something in my setup? It was really quiet and the mic was pretty dang close...
 
Although the Oktava is a decent mic, it is not known for high output, it should be reasonably quiet, but will not be as quiet as a Sennheiser MKH 40 or even some of the well specced cheapo mics.
The volume issue might be related to impedance matching, but more likely you just need gobs of clean, quiet gain. Record to a flash recorder in 24 bit to give yourself some room to boost the signal (but you may boost the noise), or maybe try a Zoom H2. If you really want quiet, line level sound, go with a better mic or go with a cheaper mic with a better noise spec. The CH1 may not have the quietest gain, but I have never tried it. But I have used an Oktava with a good preamp and did OK.
 
Maybe you were using one of the Chinese knockoffs. The Oktava is quite quiet. The camera is much more likely to be a noise source. It is also not a particularly low out put mic. Again don't know what you were using but the Oktava was hotter and quieter than the Sennheiser I was using MKE40.

No matter the specifics it's not going to be the problem that is described unless it's broken. It does need 48V phantom and that might be a problem if the camera is putting out a lower level. I would check the mic with another recorder since it could be broken. I would also try a different mic and see if there is a difference. 24 bit doesn't give you anymore "room to boost" the signal than 16 bit does, and yes boosting will boost noise. You need to record hotter and so you need to find out if it's the camera, the mic or a bad setting.

And "noise specs" are close to usless. They would be very useful if they were done in a standard way but everyone does them in a way that makes them look good. They are measured on different scales and weighted in different ways so it's difficult to impossible to compare most mics noise specs. in a meaningful way. Complicating things is that the noise in the spec isn't nec the noise you need to be concerned about. Noise being a problem has a lot to do with the kind of noise and the spectrum of the noise. So while in general the noise spec may give you an indication of the probable noise level of the mic listening is the only real way to tell how much the # reflects a reality you need to worry about.

DrDave said:
Although the Oktava is a decent mic, it is not known for high output, it should be reasonably quiet, but will not be as quiet as a Sennheiser MKH 40 or even some of the well specced cheapo mics.
The volume issue might be related to impedance matching, but more likely you just need gobs of clean, quiet gain. Record to a flash recorder in 24 bit to give yourself some room to boost the signal (but you may boost the noise), or maybe try a Zoom H2. If you really want quiet, line level sound, go with a better mic or go with a cheaper mic with a better noise spec. The CH1 may not have the quietest gain, but I have never tried it. But I have used an Oktava with a good preamp and did OK.
Click to expand...
 
Make sure the 10db pad which comes with the Oktava is not attached between the mic capusle and body. If so, it would cause that exact problem.
 
MKH 40 (not the MKE 40) is way hotter and quieter than any Oktava small diaphragm mic ever made due to the unique push pull characteristics of the Sennheiser RF microphone capsule. You can read about the tech here http://tinyurl.com/yje277q
I personally have measured the specifications of these mics using highly accurate equipment and I can assure you that they run around 6db hotter than the Schoeps, which have better output than the Oktava, although the Schoeps are great mics and I use them all the time. As for 24 bit vs 16 bit, 6db of gain is worth around one bit--depending on your gear--so 24 bit does in fact give you way more room to boost the signal, which is why digital limiters are so rarely built into high end converters. There is no difference between that and enlarging a foto. You will magnify any noise in the photo, but the resolution allows for more zoom.
Also, if you read the specs of the Canon, in HDV mode you are not recording true 16 bit, it is MPEG, which is even worse for any kind of gain normalization.
 
mainstreetprod said:
Make sure the 10db pad which comes with the Oktava is not attached between the mic capusle and body. If so, it would cause that exact problem.
Click to expand...

How do I know the 10db pad when I see it?

I am REALLY hoping this tip provides the solution but I'm trying to make sense of the mic components...
 
Thanks everyone for the tips and Mainstreetprod for what seems to be the solution in this case.

Gonna run some tests...
 
Quick question though, why would anyone WANT to use that -10db corrector? Wouldn't it just be easy enough to turn down the signal on the camera?
 
And to all the fans who were hanging on the edge of their seats for the results of my tests...

That appears to have solved the problem.

Doh!
 
If you have a loud sound source, the -10db pad will turn the mic down BEFORE it gets to the input of the camera. You can still distort the input even though you have the levels turned down. So if you are recording a rock band you may want the pad. Also, check if you have a "trim" adjustment on the camera in the audio section. That is a way to adjust the signal before it gets to the main "level" adjustments. You never want to turn the levels all the way up. In most nicer cameras you put the level at 50%-75% max because beyond that you are just adding noise. Set levels to 50% then adjust the trim to boost the level. This is also the reason we use mixers. A good mixer will give you many DB of gain before it gets into the camera, and will allow you to keep the camera's levels down, and subsequently the noise level down too.

If what you have recorded is way too low you can turn up each clip all the way, then if that's not enough you can copy & paste the clip a second time and place it in the timeline right under the original to double your volume. You could also normalize or boost your levels with the plug-ins of the editing software, but I don't want to get into all that.
 
The -10db pad thing happens more then it should... I knew this was the problem the second I read the opening post... what happens is people buy an Oktava and see 3 pieces to screw together in the little box... they put all the pieces together and think "there's my mic"... without knowing that little thing in the middle is a pad.

You will use that eventually... for recording a live band or racing or some other really loud event... but not dialog.

Better luck next time... still... at least it's not too hot... you can always raise it over and over... raising the noise-floor of the original recording... and people will think the mic/recording was hissy... and at least you'll have intelligible dialog... (trying to look at the upside here)...

Lesson learned (I hope).
 
Just to add, but aside from clipping the input of recorders, the input pad also helps prevent clipping the mic itself.

For example, the lav's used on Broadway musicals have pads built into their design as Broadway singers clip normal lav mics by being way louder than any normal talking person.
 
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