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Old April 23rd, 2004, 11:18 AM   #1
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Mixing sound for video - hall ambience at concerts

Is there a preffered way to pick up ambient sound in a hall and mixing it with th PA feed from the in-house sound technician, thus creating a believable "live" feeling, without too much reverbation?

We work on mulitcam productions in a fairly large hall, capable of holding around 1000 people. These productions are most often concerts of various kinds. We tap into the PA-feed, but due to the sterile and artificial quality of sound mixed for distribution over a large PA system, this simply won't do for video recording or web streaming. We have tried to supplement the PA sound with a couple of condensator microphones mounted various places in the hall, and mixing these channels into the finished product, trying to create the hall ambience needed to make the sound feel real. The results have ranged from bad to tolerable, but seeing as none of us would resemble a sound technician, even on a foggy day, I would be grateful if someone could point us in the right direction.
Eivind Vaa
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Old April 24th, 2004, 12:43 AM   #2
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the way uve described using multiple mics if probably the best way.. IF you were prodicing to encode as Dolby Digital surround.

if your doing a downmix, you may get the sounds mushing up and its not that pleasant to lsiten to...

if u can get a raw recording, and add the reverbs in post, that might be another solution for you.

mind you to get an accurate reverb, youll need to measure the venue and create a preset setting... this is cheating thou

what you have descibed aboutt the multiple mics IS the best way..

whay i woudl do is cut out the lower frequencies and then measure teh distance between the initial sound and the delay. The sound will always change dependin on PA set up and the amount pf people in the vebue itself... (ambient sounds like coughs, and claps etc.. ) What i mean by always change is also reverberation within the hall being that if ther eis an prop or an object or even someone walking past the mic...

I would suggest this..

Live feed from PA (standard stuff)

Mic feed from the rear Maybe another stereo pair

mix as 5.1 with Metadata/Dolby Digital EX dropping rear surrounds about -12db when mixed down

To cut down on the reverbs, i woul dsuggest moving yoru mics closer or above the audience.
This will offer a more accurate rendition as your audio will sound as it was intended .. for a live audience..

Most venues set up their audio in a manner which the audience seating is the optimal listening distance (youll notice this with Orchestra instrument placement too)

in the end, i would suggest you experiment with various live settings. and if theyre unsatisfactory, taking a measuring tape and then going Post with the reverbs is ur next solution.
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Old April 24th, 2004, 08:03 AM   #3
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Well I'm certainly no audio guy either, but I do tape our performances. I use a feed from the the house board on one channel and a camera mounted mike on the other (Sony ECM-NV1 as supplied on the PD-150 and PDX-10). Now since I don't have any fancy audio equipment I just use a very simple trick which seems to get the job done.

I'm often shooting from the back of the auditorium which is a little over 100' from the stage. Problem is that there is a noticeable and disconcerting delay between the audio from the stage system and the camera mike. Using a very rough estimate, I assume it takes about a millisecond for sound to travel a foot. Therefore at 100' you get 100/1000 = 1/10th second delay. Now that would round off to 3 frames of video. So when I edit I move the audio track containing the camera mike forward by 3 frames which brings it back into sync. Depending on preferences you can also try moving it by either 2 or 4 frames and see which amount of reverb you like the best. But my "rule of thumb" is to advance the camera mike's track by one frame per 30 feet of distance from the stage. Finally, when I edit I blend the two tracks to create a stereo image that I like, such that the house system is the larger proportion of each.
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