AC130 Audio Settings???

[Chris Harding]

Hi Guys

Has anyone fathomed out the mysteries of the 130's audio channels yet.
Problem 1 :
The manual shows the level meters with two lines, one marked -12db and the other 0db. In my screen I only see one line which is presumably the -12db mark??? I am just guessing now but does the display go into red maybe at the 0db mark???.

Problem 2 :

If you work in auto for the XLR's the camera doesn't seem to clip a big signal evenly at all..it almost shaves the top off the waveform and leaves the bottom untouched!! Auto is sometimes useful at weddings but for now I stay in manual

Problem 3 : The Manual says the 130 has a record level 8db higher than broadcast shoulder mount cameras??? Coming from my HMC80's I have found that I need to LIFT sensitivity by around 10db to get the same sort of signal as I'm used to so does the 8db higher record level mean that the 130 needs a higher or lower signal level ...I read it meaning the 130 is 8db more sensitive but in fact it's completely the opposite!!

Problem 4 :
You can turn on audio limiters for both XLR channels and they only work in manual...however in manual you can push the audio level comfortably above 0db so it's constantly in the red and AFAIK nothing seems to be limited at all. Anyone know when the limiters are supposed to kick in??? I would have thought at the very least, levels higher than say -4db or even -6db should be limited but the limiters have no level settings..just on or off.

Any bright comments from 130 or 160 owners...even HMC150 owners ???? maybe they are the same???

Chris

[Josh Bass]

Regardless of markings, 0 should always be the very end/top of the meter on the DBFS scale, which it seems like all modern cams use. . .there is nothing beyond. You hit 0, you done got yourself some distortion and anything higher would be useless.

Only exception I can think of, and I've never seen this on a camera meter (maybe an ancient Beta cam), is older analogue type meters where 0 is the "target", and +20 is your absolute top.

[Josh Bass]

Regardless of markings, 0 should always be the very end/top of the meter on the DBFS scale, which it seems like all modern cams use. . .there is nothing beyond. You hit 0, you done got yourself some distortion and anything higher would be useless.

Only exception I can think of, and I've never seen this on a camera meter (maybe an ancient Beta cam), is older analogue type meters where 0 is the "target", and +20 is your absolute top.

I've generally tried to have my meter bouncing around -12/-10 for most peaks in normal speech.

[Chris Harding]

Thanks Josh

That's what I have assumed... when the level line block at the end goes red I figure it's hit the 0db mark..I always keep mine hovering just over the -12db line.

Any idea why the "auto level" brutally slices off the positive side of the waveform only??? That has me beat as well as why they bother to have audio limiters that don't limit!!! Unless the limiters are just supressing peaks that occur way over the average level (like a slamming door during an interview??)

Chris

[Chris Hewitt]

Hi Chris, that's very weird...I have only just PM'd you about audio settings and here you are talking about limiters.
I shot a wedding last weekend with the 160 for the first time, a Rode NTG2 on Channel 2 and an old radio Sennheiser lapel mic on Channel 1. The Rode on phantom (at-50db) was very quiet in post while the Sennheiser was jumping all through the red (again at -50db setting). However, there was no audible distortion but at the loudest parts (applause), you could definitely see the limiters kicking in on the Vegas VU's.
I do tend to push my mics and always enable onboard limiters. I'm using AC3, not PCM on the camera as Vegas can't see PCM and I haven't got round to finding out why yet.
Hope this helps.

[Chris Harding]

Hey Chris

Thanks got the PM as well thanks!! I'm assuming you were shooting in manual audio??? I shot a wedding last weekend and the weekend before and on my fixed camera I had both channels being fed by two Azden radio mics...in error the system on the mic stand (used for readings) was at -50db and the grooms mic system was as -40db. With both channel gain controls at midway the grooms mic barely made the level meter get to within half way towards the -12db mark on the meter so the signal was really low!!

In Sony Vegas to get the celebrant's words (she was standing about 6' from the groom)..I needed to lift the signal by 14db!!! The 2nd mic system had a beautiful signal .with the gain at midway I was almost over limits and had to turn the gain down a tad!!

I still cannnot fathom out the so called levels on the camera!!! The Rode VideoMic has a sensitivity of -38dbA yet at -50db camera gain the signal is still very low.

I'm shooting an outdoor wedding today in a few hours time so I'll run the radio mics at -50db now and what I will do is run the Rode on the 2nd camera (just using that for cutaways) at -60db and see what that audio looks like.

Chris

[Chris Hewitt]

Almost the same situation as me, Chris. I always shoot with manual audio for the mics. Do you run a limiter on your master out in Vegas? I run an L2 set at -3db on the threshold and -0.3 on the ceiling so no clipping in post and find that helps a lot for a consistent sound from one project to another.
I've pm'd Rode to ask their advice regarding the db best setting in camera and will post here when I hear back from them.

One more thing, Chris...do you edit the avchd natively in Vegas? I have a Quad core PC with 4gb ram on Win XP (3) and with 1920i PH clips, my system really struggles so I use Gearshift to work with proxy files but it's like being blindfolded.

[Chris Harding]

Hi Chris

I shot yesterday with the cam at -60db sensitivity and it's a little high as it peaks a bit into the red with loud voices. Remember this was ONLY doing wedding interviews where I have a single person talking...at noisy receptions I found that -50db works well but since the Rode VideoMic is rated at -38dba I was surprised that the camera has to be set so high!!

Yep I have clips directly on the timeline and they run fine on my machine..however I'm running an i7 2600 with 8GB ram and it's 64 bit and the 64 bit version of Vegas 10 too!!! Prior to that my computer was only a 2.2GB DuoCore with 3GB Ram and WinXP Pro and it struggled to keep up. What I was doing there was not using Gearshift at all but converting my AVCHD to 50mbps HDV using Upshift. You seriously will not be able to tell the difference between clips but it does occupy a bit of time for something like a wedding!!

Chris

[Josh Bass]

Have you guys thought of taking the cam to a rental house or find some other way to get your hands on a mixer like the Sound Devices 302, and do some tests with that?

I'm not a sound guy, but seems like if you ran tone on the mixer, set that tone to 0 on the mixer you're using, and set the camera so that with the audio pot on unity gain (usually halfway, so if it goes from 0-10, like an EX1's, unity would be with the dial at 5), the camera's meter reads -20, whatever settings you have to tweak in the cam's menus to make that work, THAT should be the right menu setting for the audio.

If you did this test and had to crank the cam's pot to get the meter to read -20, something's wrong. If you had to turn the pot way down to get -20, something's wrong.

This is my "non-audio guy just thinking off the top of my ass" suggestion/advice. Cause me personally, I have no idea what those trim settings like -50, etc. in the menus on these cams mean, and neither do I understand what the output rating of the mic, as you've described it, means. But the test above sounds reasonable to my caveman brain.

I have a client with an EX1 that we use frequently, and I've noticed we usually have the audio pots way up (toward 10, the max) to get proper speaking levels with Lectrosonics lavs during talking head interviews. Manual says 10 on the audio pot is +12dB gain. That just doesn't seem right.

[Chris Harding]

Thanks Josh

I was simply querying the statement that the 130 has an "8db higher recording level than broadcast cameras" It definately seems the other way around...maybe it's a Japanese translation problem???

Ok I found during two wedding shoots over the last two days that with my Rode VideoMic with a spec output of -38db and not attentuated at all needs to be set at -50db for general audio ..like a bunch of people taking that has a reasonable level. Doing a one or one "interview" about 10 ' away from the camera I found that -60db is a better setting but admittedly I COULD have turned up the gain control which was left at "5"

All that seems to work fairly well but compared with my other cameras the sensitivity does seem low.

I just would have thought that IF the mic has a know sensitivity of -38db then setting the cam to -40db would be logical...however the fact that it's -50db now is not important at all..as long as it works!!

Chris

[Josh Bass]

I don't know about all that. . .

As I said, I'm not an audio guy. I know just enough to know some of the tech-y audio stuff is more complex than it seems.

For instance, you talk about "dB" a lot, but the thing is there are like 20 (I may be exaggerating) different units of measurement that one could mean when saying "dB". . .dBv, dBu, dBm. . .etc. What are they? HELL IF I KNOW! I just know that you can't simply add and subtract the numbers and get an answer, most of the time. Unless your mic manufacturer and the manual/camera menu are talking about the same unit of measurement, adding/subtracting may not mean squat.

Another, even simpler test than the one I mentioned with the mixer might be to simply hook up a lav to someone or boom them from the proper distance of 18-22" with a boom mic (btw did you say something about doing an interview from 10 FEET away? I would never have a mic that far away from a speaker. Way too far for any mic), and with them mic'd boomed correctly, adjust your menu settings so that your dial is, ideally at unity (halfway), but definitely no less that "9 o'clock" on your pot (otherwise you're having to attenuate too much), or more than 3 o'clock on your pot (otherwise having to crank it too much), to get a proper level on your meter for normal speech.