Audio and the AF100

Shooter

Shooter

Veteran
We are leaping into the murky world of audio and need some help please.

I know there are some here that know a bit about audio and would prefer to ask here instead of in an audio forum ( where I get baffled, confused and bewildered easily).

We have invested in a little more basic sound gear to cope with a little line of fun work that precludes the use of our normal audio pros freelancers. Cost.

Filming musicians ( piano and accoustic instruments) in recital and for competition entry purposes.

Intention is we do the audio recording our selves and its not an area we are totally un familliar with but... we do have questions. We have never had or used our own field mixer before.

Will be inputing to AF100 at Line Level ( like the pros)

Our new FIELD MIXER (Azden FMX-42a) outputs 1khz tone @ +4dBu. What does that correspond to on the AF100 meters? (0dB or 0dB +4)

We are considering twin mic'ing the grand piano and recording both as mono on separate AF100 audio channels (mic placement is not an issue). Twin mics to capture high and low end of the piano

I feel more confident having two discrete audio channels as opposed to mixing them in the field. Anyone got advice on that please because I am a bit worried about phase cancellation in mono when I combine them. ( If I need to combine them)

We only have mono mics...how would one manage stereo with the AF100? (* the kit intended for these projects)

Our Audio kit:
* Azden FMX-42a
* Avan CK-7 Condenser Mic (3 pattern switcheable)
* Sennheisser E835s
Sony Wireless Mic x1
Sony Shot gun mic x1

I am thinking -6dB for peaks is a good target? What do you guys think?

BTW: will be doing tests up to and including the first of these shoots ( next weekend). Just waiting for the mixer to arrive. ( I have the manual already).

Any advice gratefully received. Thanx
 
Shooter said:
We are considering twin mic'ing the grand piano and recording both as mono on separate AF100 audio channels (mic placement is not an issue). Twin mics to capture high and low end of the piano

I feel more confident having two discrete audio channels as opposed to mixing them in the field. Anyone got advice on that please because I am a bit worried about phase cancellation in mono when I combine them.
Click to expand...
To avoid phase cancellation when dual-micing a single instrument, it's best to vertically overlap the mics in a crossed configuration, with the mics pointed at the two areas of the instrument you want to emphasize. The Sennheiser E835s has a cardiod pickup pattern that will reduce crosstalk between mics when they're placed at right angles to each other.

Here's a link that illustrates the technique:
http://www.wikirecording.org/XY_Stereo_Microphone_Technique
 
when sending tone from the mixer, set the audio levels on the AF100 to -20db or -18db. +4dBu is 0VU standard.

i would xy and place the mics a few feet from the top opening. place your head in that general area. where it sounds good, place the mics.

here is a good article on where to mic a grand piano.

http://www.doghousenyc.com/articles/piano1.php
 
I am appreciating and absorbing all the info. Thank you all.

Thats a great article at doghouse BTW.

So much to learn...so little time!
 
I don't think those mics are going to cut it.

You're going to want to use two matched small capsule condensers in an X/Y (or other stereo configuration). Mind the 3-1 rule if
you go with a spaced pair. If you can rent a pair of DPA's (aka B&K's) .. those kill on pianos.

Here's a recording I did with Tony Shepperd for a project. We used B&K's into Neve 1081's

http://techbreakfast.com/video/raydavis_finalcut2_Techbrea.mov

(Please excuse the audio in the beginning .. this clip doesn't have the lav mic audio (for some reason).
Note the placement and angles of the B&K's ( 6" back from the hammer action ).

An option is to use a third large capsule condenser at the bottom of the grand about a foot back from
where the "U" bass string bulge is on the harpboard. Finding the "sweet spot" on the harpboard for
the bass takes a little hunting. If you don't have a third, I would opt for a good stereo image off
the piano (back from the hammer action) over trying to balance bass/treble .. that you can do
with EQ in post. You can't fake stereo imaging.

To be honest with you, when we record musical performances, we use our Protools rig and don't use the audio
on the camera except for redundancy or sync. It's so much better to go into post with discrete audio
feeds from each of the instruments.

Could you hire an audio engineer to record for you? If you weren't in frickin' New Zealand I'd do
it for you :-)

jeff
 
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breakbeat46 said:
when sending tone from the mixer, set the audio levels on the AF100 to -20db or -18db. +4dBu is 0VU standard.

...
http://www.doghousenyc.com/articles/piano1.php
Click to expand...

Please clarify for the dummy as he slowly gets confused.

You are saying I run the tone out from the mixer and I input that at 3 to 4 dashes (each dash is -2dB correct?) under the -12dB line on the AF100 to get -18 /-20dB.

So when recording the performance...where on the mixer VUs am I peaking the audio?
 
Shooter said:
Please clarify for the dummy as he slowly gets confused.

You are saying I run the tone out from the mixer and I input that at 3 to 4 dashes (each dash is -2dB correct?) under the -12dB line on the AF100 to get -18 /-20dB.

So when recording the performance...where on the mixer VUs am I peaking the audio?
Click to expand...

Most studio and recording equipment have a +4dBu as a 0dbV reference standard. Don't sweat that too much .. it's
like saying NTSC "black" vs. true black .. it's just an agreed upon calibration reference.

For your purposes, the most important thing is to set the AF100 to line-level input and balance the Master on
on the 42a vs. the input gain on the mic pres to:
a: find the least noise between pre-amp gain and line output.
b: stay below -6dbu on the AF100.

Just remember the more gain you apply through the mic-pre, the more you raise the noise-floor.
If you crank the mic pre and reduce the master ... that's typically not so good.... On most
field mixers, setting the master 1/2 way is a good starting point.

What I worry about with field mixers is the noise the phantom power circuitry adds. They
have to use a voltage stepper to get AA battery up to 48V .. the DC tends to be noisy. The exception
to this is Sound Devices MixPre...

jeff
 
Here's a recording I did with Tony Shepperd for a project. We used B&K's into Neve 1081's

http://techbreakfast.com/video/raydavis_finalcut2_Techbrea.mov
Click to expand...

damn, that was some clean sh*t.

i think for most of us, we have to use what weʻve got. iʻve found sticking a shotgun overhead of an instrument or pointing in the general area of itʻs sound hole adequate for most clients. if its a client with expectations of the audio sounding like an album, then i would sub someone with the proper studio recording gear, like jmarkham.
 
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Thanx Jeff.

All brilliant and helpful info and advice.

This particular exercise is really a budget thing (as in no budget - $500) ...but also its kind of interesting in itself that it gives me an opportunity to learn a bunch of new stuff that I thought I did not want or need to learn. It also has some on going potential.

Keep in mind the project : Filming musicians ( piano and accoustic instruments) in recital and for competition entry purposes. These are normally done for this "client" by a guy with a camcorder and an on board mic. Dynamic mic at best.



I really do want to stick to my business model which means employing the right guys for the job and that especially means audio guys of which ... I have acces to great guys that I have worked with for years. It also means I dont want to invest in a bunch of great audio gear ( well I would like to actually) when I have access to it thru' my pro audio guys. My money is best invested in camera and lenses and monitors and a new Ducati....

I am a bit of a believer in only giving the client what they can afford or are willing to pay for...but I always try to give them more to meet my own standards of what I am willing to out put as quality.

Jeff. Tell me honestly. Can I record a grand piano with a single mic.? eg Avant CK-7 in figure 8 polar pattern.

I am here at the studio today ( Saturday) doing various mic tests with the AF102. The mic seems great. Clear, clean, warm. (on the Mic input currently)
I dont have the mixer until Tuesday so cant test the Line input workflow with the tone generator.

I wil be doing tests with another grand piano as soon as I have the mixer.

Cheers
Craig
 
Hey Jeff

That Ray Davis stuff is really cool. Nice gig

Thanx for referencing and linking it.

Craig
 
Shooter said:
Thanx Jeff.

All brilliant and helpful info and advice.

This particular exercise is really a budget thing (as in no budget - $500) ...but also its kind of interesting in itself that it gives me an opportunity to learn a bunch of new stuff that I thought I did not want or need to learn. It also has some on going potential.

Keep in mind the project : Filming musicians ( piano and accoustic instruments) in recital and for competition entry purposes. These are normally done for this "client" by a guy with a camcorder and an on board mic. Dynamic mic at best.



I really do want to stick to my business model which means employing the right guys for the job and that especially means audio guys of which ... I have acces to great guys that I have worked with for years. It also means I dont want to invest in a bunch of great audio gear ( well I would like to actually) when I have access to it thru' my pro audio guys. My money is best invested in camera and lenses and monitors and a new Ducati....

I am a bit of a believer in only giving the client what they can afford or are willing to pay for...but I always try to give them more to meet my own standards of what I am willing to out put as quality.

Jeff. Tell me honestly. Can I record a grand piano with a single mic.? eg Avant CK-7 in figure 8 polar pattern.

I am here at the studio today ( Saturday) doing various mic tests with the AF102. The mic seems great. Clear, clean, warm. (on the Mic input currently)
I dont have the mixer until Tuesday so cant test the Line input workflow with the tone generator.

I wil be doing tests with another grand piano as soon as I have the mixer.

Cheers
Craig
Click to expand...

Yea Craig, you can do it with a single microphone. The Avant CK-7 is your typical Chinese capsule mic in that they may get
a little bright in the 10kHz range and need to be cooled back a little in post. Be mindful that a figure-of-8 polar pattern underneath
a piano lid will likely give you phase cancellation issues as the sound reflecting off the back of the piano lid will be 180 degrees out
of phase hitting the back of the capsule and cancel some of the in-phase waves going in the front of the capsule. It may sound
thin and/or have comb-filtering artifacts. I would opt for a cardioid pattern and try and place the mic far enough away from the
harp such that you get good sonic coverage. If you have access to a PZM / boundary mic .. those are often used either under the
lid or on the floor to catch the reflection of the lid down. That's another "single mic" technique that works well . but requires
a fairly quiet environment.

I dig what you're saying .. great audio guys can do amazing things with whatever they have at their disposal.

jeff
 
Jeff.

Thanx again for educating me and taking the time.

Can you tell me how the polar pattern works on the other axis. ie. Assuming the pattern shown in the diagrams are "X".. .what happens on the "Y" axis?

BTW...my tests today have shown how inadequate my headphones were , particularly when monitoring in proximity to the source of the sound , and that forced me to go out and spend NZD$300+ on some Sony MDR-NC60 cans. Noise cancelling. What a difference and how comfortable!

Audio is as expensive as photography it seems!
 
Audio is a whole 'nother obsession .. one I am afflicted with :-)

Dynamic and condenser microphones are very much like lenses. They have focal symmetry much
like a lens in the direction that they're aimed. The "Y" axis opens up the further away from
the capsule you go. That said, the majority of the information comes from the principle direction
that they are aimed. Off-axis info comes in via reflections off of other surfaces. This is a
good thing .. as it's the way our ears work too.

Therefore, polar pattern charts for mics are 2D ... they only measure the rejection/response in the plane
the microphone is aimed at.

hope that helps ...
jeff
ps: for audio monitoring in the field, I've taken to the Shure 535's .. the outside noise rejection is great ... sometimes
too good when you can't hear people yelling at you :-)
 
Your posts and info have been very clear Jeff.

I understand "audio recording", much better now.

Thanx
Craig
 
Everyone has been very helpful..and now I actually have my field mixer...I am putting into practice all the great advice given.

Working out real well and I am having a lot of fun getting this together

...but I have to ask... What do sound guys think about the VU display in the AF100?

My own opinion is that it does not make it easy the way it is implemented. eg. You can not see any of the dB increments until you actually have a signal that "touches it" then they dissapear after a brief ( but helpful) lag. There is no reference showing the -12dB or the 0dB until you get there. The little dashes and 2 bars seem woefully inadequate.

As for the audio level control input controls...fiddly, fiddly.....

Should have been done better methinks!

Here I am ..a week into being a "soundy" and having a whinge already!
 
I don't have nearly the experience that Jeff has, but I always want outboard audio, even if I'm going to mix sound and send it to the camera. I like having the raw channels recorded so I can go back and adjust the mix if necessary. That way, the in-camera audio is there if the mix worked, but if not, I can remix in a pinch. - Tim
 
Hullo - First post here.

I'm an audio guy who's gotten into film, so I have some thoughts on the subject.

I completely agree about using outboard audio and syncing it to the audio captured by the camera. For most things the onboard audio is fine, but for anything critical, I would consider the audio on the AF100 to be mediocre. The preamps in the field mixer will help, but the main issue is the analog to digital converters in the camera. I'm used to extremely nice Apogees, but have used some of the cheaper models as well, and while I don't expect something portable to match them I do expect them to be reasonably accurate. The onboards sound like they're targeting the timbral range of the human voice, which makes sense, but does a disservice to anything outside of that range (let's say 300hz to 2k, with a significant emphasis on 2k). Pianos sound like pianos when they're well recorded from 20hz-16khz. Unless you have that, you're asking your audience to fill in the gaps. They usually will, but it's a different experience.

Plus, the gain stage on the onboards seems to be placed after the A>D conversion, instead of before, so there's some artifacting and a danger of clipping with anything loud.

On a budget, I'd recommend a Zoom H4 over the onboards - they are much, much flatter, not hyped around 2K, with significantly more dynamic range and none of the compression. Apogees they ain't, but they get detail that the onboards miss. You can also record at 24/96, which will allow you much greater flexibility in editing. If you screw up, that kind of dynamic range can save your bacon.

Again: For the amount of circuitry and power it would take to do it right, I can understand it not being there and don't fault the camera for it. Most of the time it's going to get the job done nicely. But you're talking about recording audio-centric material.

As far as recording with 1 mic goes, sure. If you're not going for a stereo picture and have a decent mic, why not? Someone up thread recommended sticking your head in and finding the sweet spot and that's a pretty good start. In the same way that lenses aren't eyes and alter what they record, mics aren't ears. Too close to the sound source and your bass will be amplified. Too many off-axis reflections and you can get phase and comb filtering issues. But moving your head around (with one ear plugged, since you're doing mono) and finding a good spot is a great start and will most likely get you where you need to go.

If you do want to create a stereo field, then go with the X/Y. Think of that as your wide shot to establish the scene - if you only had one shot, this is the one you would go with. Symphony orchestras are generally recorded this way (although with extremely nice mics).

Figure-8 mics are great for room recordings, not great for miking an instrument (with some exceptions). because the mic has a front an back, you run the risk of phase issues, as well as not getting the kind of focused sound you might want. It will totally depend on your set-up in the room.

One last thought: I've always gotten great results from taping an omni to the floor or wall. The result is functionally a PZM, but with a better capsule. I have a couple of cheapo Cascade omnis (M37s - under $100 and worth twice as much) and I do this trick all the time. Quieter acoustic instruments it might not be great for, but piano, drums, rock bands, even acoustic guitars it can sound great.

Have fun with it and be critical. If it doesn't sound right, try something different.
 
Shooter said:
...but I have to ask... What do sound guys think about the VU display in the AF100?
Click to expand...

I think they've prioritized them in the realtime processing space too low. They're
very very slow. The peak may show up .. but it can be quite a bit later than
the audio that actually peaked the sound-chain.

So .. I don't trust them other than to say that there was a problem somewhere.

You can't tune a sound path with them.

jeff
 
Thanx for all the additional info and advice.

Be very interesting to hear a side by side test between the onboard and a Zoom. We have one so will try and get around to testing it one day.

Doing my piano gig today. Definitely will record to the onboard though. I would not trust the Zoom to hold synch over a 40 minute continuous performance.

Jeff... the thing I really dont like about the VU display is that it doesnt show the Range of increments. The entire Meter could have been "Ghosted" so that one saw it all and the levels overlayed on the meter. I find myself trying to count the dashes! ( 2,4,6,8 or -2,-4,-6,-8 ...) That they are on then off does not help.
 
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