Dolby Digital 5.1 and Vegas
 

Hi,

I have an Alesis Firewire 16 Mixer and I am awaiting the arrival of 6 Sony F112 Omni-directional mics.

The idea is to go to an event with this gear, plug in all of the mics into the Alesis unit (although they will be fitted with Sony's new UWP-C3 Series UHF transmitters), record each (mono) channel seperately (using Vegas of course), and then add this audio to the video in a 5.1 Surround Project and pan and do the necessary etc.

My question, I suppose, is mainly the positioning of the mics i.e. 6 mics (5.1) - should they be positioned (assuming a large hall or conference centre) sort of front left and front right of the venu, rear left and rear right of the venue, centre mic at the podium (and where to with the .1 or 'subwoofer' mic)?

Am I on the right track? Is it that simple?

Anybody doing this or done it before please comment.

Regards,

Dale.

I'm sure a more experience person will soon jump in, but having a 5.1 product does not necessarily imply the presence of five mics. You can use as many, or as little as you want, then pan as you please. The exciting part is deciding how to position the mics, and that is something of an art. You don't just put them in arbitrary positions! The LFE channel (0.1) is not recorded, but generated from the other channels by using a lowpass filter (i.e., extracting the low frequencies).

The Schoeps website www.schoeps.de has a pdf file download of a good white paper on surround mic techniques. Well worth reading even if you don't own Schoeps mics.

Thanks for the replies and (Steve) thanks for the link.

Boy oh boy - I could not have been more wrong about mic placement!!!

Emre - thanks also - and you are quite right about the LFE channel - I did not think about that but should have figured it out.

Anyway - still dying to try!

Anymore ideas - very much welcome!

Regards,

Dale.

and there isn't a subwoofer mic. the ".1" subwoofer channel in a surround setup just gets everything from the whole mix below a certain frequency. you choose this frequency when you setup your surround receiver, based on the room and the freq range of the other speakers in the system. that's why it gets a decimal point- it's not a discrete channel, just all of the low stuff, since subwoofers are better able to handle low frequencies than the smaller satellites in a 5.1 system. since bass tends to be less directional than higher frequencies, this doesn't usually detract from the spatial feel in a 5.1 setup. hence, people throw their sub in a corner, behind the couch, whatever, since the real low stuff is "felt" as much as heard.

i just realized before hitting "submit" that i just re-stated (less efficiently) everything that emre said, but i'm going to hit submit anyhow since i've typed the bloody thing.

the above applies if you are ESPN encoding circle surround (did *I* really say that?!)

ahhhh, but in reality it's a .1 channel because it's not full BANDWIDTH. it is however a discrete channel (in true 5.1 applications) and you can steer anything you want there. just realize it only has a bandwidth of about 5-200Hz when it gets to the end user...

Thanks for the information and advice.

I have been playing around with a 5.1 mix with LFE and get the idea of the .1 channel (I always wondered why some commercial DVD's sounded fantastic on home theatre when Dolby Digital 5.1 Surround was activated and others sounded terrible until you deactivated 5.1 Surround and activated the 2 channel surround mix - now I know!)

I have had a look at the Schoeps website and will try some of their configurations as soon as my equipment arrives.

The only thing I don't get is where do you put the whole mic contraption at the venue i.e. do you put all the mics in the centre of the venue or close to the stage or what? Is it supposed to be placed where the intended listener would be sitting in relation to the live setup?

I mean it would be pretty easy to judge if an orchestra or band in a hall was your shoot but mine will be conferences and the like.

While some may feel that for my type of application 5.1 surround sound may be an overkill but I like that sort of spatious, reverberated audio particularly for speeches and the like and do not want to simulate this with effects in post. It always sounds kind of 'official'. I should get a job as as spin doctor for a government official - I could save my self a fortune!

Regards,

Dale.

I was just listening to an interview yesterday that I did last summer and someone else took off the video and mixed for CD release. The sound was from a lav, intimate and close up. Easy to understand, very intelligible.

Last week someone gave me a class recording transfer to CD. Great large diaphram mic, decent preamp/usb interface to a laptop. The mic was somewhere in the middle of the room - the speaker was difficult to understand, the reflected sound made his words muddy and unintelligible at times.

For someone looking for more room sound, more spaciousness, a sense that the recording took place in a large environment, there are three conventional approaches:
1) Record the sound as you want it played back, that is, with all the room sound you want.
2) Record it on the dry side, add efx to taste in post.
3) Record it in at least two channels, one dry, one wet, mix to taste in post.

The challenge with 5.1 field recording is monitoring. You've decided on #1, above. For 5.1, the best way to monitor that and choose your mic position is to have a 5.1 playback system in a separate room from the presentation, an assistant and a pair of walkie talkies, and time in the room with the speaker or someone who sounds like him or her. So, you dial in the mike array placement.

If you can't make those arrangements, you'd put it close enough to get the direct sound you want in the front channels. Whatever it is that you want to be the primary sound, make sure you get it with the front mikes. This you can monitor with headphones in the venue. Then, when you get to post, if your front channels are too dry, mix in some rear signal to the front channels, as in #3 above.

Good Morning,

Thank you very much for making things clearer for me.

I found out yesterday that my Sony Mic's should be here on Friday or Monday so I will be able to test things out (I had better start preparing a speech)!

Regards,

Dale.

surround mic techniques
 

The only way I think (kick me if I'm wrong) to actually capture a sound scape in surround (5.1, 6.1, 7.1) is the use a surround microphone (ie, Soundfield or Holophone.) But that might not be the best case. My recommendation would be to close mic everything as much as you can and leave an omni mic to pick up the ambience. Then in the mix put the speaker on the center channel, then pan the ambience to the rear channels. It actually "feels" more surround than spreading the mics around the room in hope of capturing the whole event in "surround."

Hello - thanks for the additional info.

I'm not sure that surround mics will work for me as I am not intending to go straight into the camcorder but rather I will have 5 seperately recorded channels going into a mixer and from there into Sony Vegas from where I can pan, create a LFE channel, and then render to 5.1 Surround.

Basically from the info on the Schoeps site (link provided by Steve House above) the 5 mics are placed on special mic stand (which I busy making myself) and hopefully this will do the trick.

I suppose that this is a very subjective issue. I mean - all venues and situations are not the same - so I can foresee lots of experimentation coming. I just needed some advice as a basis from where to start.

Regards,

Dale.

FYI - you can make up the stand with a couple of stereo bars, etc as long as you can get the mics into the right position relative to one another. Note too that one of the methods they suggest is a "double M/S" that only requires 3 mics and recording channels to capture all 5 channels. By doing the matrixing in post you only need to be able to record 3 channels in the field. recording Front Cardioid, Figure-8 Sides, and Rear Cardioid mics and mixing them in post to derive the 5 surround channels. The sub ".1" channel doesn't need to be recorded in the field either since it usually consists of FX that are added in post, along with bass information from the other channels split out and redirectded to the sub channel during the mix. Indeed a bigger bass problem in the field is not how to record it for the LFE channel but rather how to prevent low frequency noise from handling, vibration, air conditioning etc from being recorded.

Just occured to me, while 12-bit sound certainly isn't optimal, using a miniDV camera that allows for up to 4 channels of audio to be recorded at once plus the Double MS system of micing, one could shoot surround in the field without having to resort to a separate recorder and mixer, and double system sound.

Thanks again Steve.

As far as using a miniDV camera that will allow recording 4 channels - I have seen one or two Sony models that allow this (or should I say that I have seen surround mics advertised for these camcorders) - but - too late for me - I already have a FX1E and a VX2100E so these I have to use.

I'm still waiting for my Sony UWP-C3 Kits and Sony F112 Mics x 6 (I ordered 1 set too many). These are new mics apparantely (I'll be the first here that has any of this gear anyway) and according to the specs they have a wide frequency response but are omni-directional - do you think this would make that much of a difference (I do have 2 other Sony uni-directional mics and another 2 Sony mics with cardiod pickup patterns but they have slightly different frequency responses to the F112's)?

Also - you don't by any chance use Sony Vegas do you? I am also a little perplexed by some of the 5.1 Surround settings available in Vegas - maybe you could shed some light on the subject - see my thread at http://www.dvinfo.net/conf/showthread.php?t=62882

Regards,

Dale.

There are several different methods to capture surround/a surround soundscape without one of these devices. The configurations are well documented in a variety of articles, books, and a video.
You might check out "Instant Surround" from Jeffrey P. Fisher.