newbie question on audio levels

D

dylansmith

Well-known member
Hi guys,

please pardon me for the newbie question. I understand that levels need to be set manually to prevent clipping. For example, if we need to shoot a concert/orchestra assignment, how would we know what is the audio peak unless the performers rehearse once to let you set the levels? Also, how should we set the levels if there's a huge difference between the peak and trough throughout the concert? can the audio still be salvaged if it registered "0" at the trough? I only know that audio can't be salvaged if it is clipped, but what about the other way?

Thank you for your advice!
 
Sound checks generally have a lot less SPLs (volume) than the actual performance, so leave yo'self HEADROOM. If your recorder's level exceeds 0dBFS it is clipped.. (a few samples would usually be inaudible) but.. depending on the severity, it may be 'salvaged' with a clip restoration app./plug-in. If the microphone /input stage/preamp or is over-driven/distorted, all bets are off.. not cheap/easy.. and in many cases impossible to fix.
 
1. Set peak at -12 dB, maybe even -20 dB. If no reliable rehearsal, the first minute or so of the live concert is your rehearsal :D

2. In post, apply a Compressor audio filter (should be somewhere in your editing program) and set the ratio to like 3:1 or even 2:1. Whatever sounds good. That will make up for the peaks and valleys, and it will raise the volume overall.

3. Try to test this, somehow, on a day well ahead of the concert.

More: How to Set Audio Levels, by Sam Mallory
 
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That is why the dress rehearsal is for the people who are RECORDING the event just as much as for the performers. Unless you can set levels during the rehearsal, you really have almost no ideal where to set them. And, as Rick said, always plan on the actual performance being at least 3dB hotter than the rehearsal. And this is why we prefer to record with 24-bit dynamic range, to allow adequate headroom during live performances, especially when recording amateurs.
 
what about in situations where there are no rehearsals (e.g. actual wedding documentaries)?

how do i know how much dynamic range my recorder has? I'm currently using the Zoom H1 and intending to switch to Rode VideoMic to save time on merging audio/video files.
 
For spontaneous recordings, if you have the budget, you have a sound person who knows the equipment and how to use it (and typically has been there and done that dozens of times before and can predict how equipment will perform).
And if you don't have the budget, that is why we have auto-level. Of course it makes a mockery out of proper music, but how many weddings have proper music anymore? Of course there is no excuse but laziness for not experimenting with your gear to know how it performs in various light and sound levels.
 
There are a couple of ways of dealing with the no rehearsal problem. Unfortunately they involve experience and or money. What I would do is use a MixPre with the limiter and set it up so the recorder is "unclippable". Aim at what experience tells me is probably in the ballpark and then adjust as I go. But that I suspect is not an option for you. I don't know your recorder but many have a split level record mode where one copy is recorded well below the other. That might help. Otherwise about the best you can do is ride levels and figure the start is going to be rough.
 
I like to run things hot, so set things I set things to -12 and go. Adjust on the fly as needed. Being able to handle this comes with experience, and having good quality gear is necessary.
 
I always peak at -12dbfs on location and have done so for 35 years as it has been the broadcast standard that I have had to follow, as for setting levels you get to know with experience and you can even set a rough level just talking into the mic and then quickly making any adjustments when recording.

Most of my mixers also have limiters and these have been calibrated to make sure that things never go over -12dbfs but the gain that is on the mic amp needs to be adjusted so that you are not constantly limiting and they are doing what they are supposed to do and not on all the time.

Sometimes you need to use them more and for certain subjects such as sports they are essential as the dynamic range can be way too much for safe recording.

You can also set gain structure using a tone source as a substitute for your mic and I did a couple of videos a few years ago using the low cost behringer cable tester.

https://youtu.be/pJWKLbVZVU4

Note in the UK we use -18dbfs not -20dbfs but here is another video showing a similar test including peak levels corresponding to the USA spec: https://youtu.be/s7jG_djmiX0
 
For wedding work you will seldom if ever be able to make use of the good practices described by those who work in the TV and film fields. Its just a hard fact of life.

Ideally you would want lavs on all the participants with speaking parts. But good luck trying to get one on the bride, or female guests who are to do readings (of which there may be several), or most female civil celebrants, or some church celebrants of either sex. Or some grooms - especially if they are not that keen on video themselves or if their attire such as a tight-fitting military uniform does not really lend itself to having a lav+transmitter/recorder in and around it (hint: you are not going to have time to fix it in his hair or persuade him to have "plasters" securing cables to his skin) Are you then going to spend on multiple radio kits, or multiple standalone pocketable recorders. How are you going to monitor it all. Do you really want a shaggy audio guy crashing around spoiling the ambiance and wrecking the compositions of the stills.

Good luck finding the time before the ceremony to set it all up and test it. Good luck hoping that everything happens when it is supposed to and where it is supposed to.

And the more complicated it is the more there is to go wrong, let alone eating into you shooting time when you have to break it all down afterwards.

For weddings you have to settle for what will pass muster rather than aiming for a perfection that you are very unlikely to achieve.

On the plus side, the quality you must reach to satisfy clients is far more achievable than the quality you would need to reach for TV and film work. Anything more is ... well ... overkill, and is likely diverting you from tasks that would benefit you more.

Back to the H1 and its levels. The H1 works great for weddings. Lots of us use them. I have 4 plus an H4n. They are quite big for sliding into a trouser pocket to take a lav but that is doable. Some people use smaller dictaphone type devices - which can also be useful to tape to a venue's handheld mic. You can hide H1's in flowers near the couple. place them on discreet tabletop tripods, clamp them with friction arms near to or overhead of the couple, clamp them to lecterns etc. Ideally you would also take a feed from the venue's board if they have one and if its accessible but do NOT rely on it. A good insurance policy is to put a recorder such as an H1 on a lightstand and place it very close to one of the venue's speakers.

As regards its actual levels, thats easier than it may seem. The screen itself is quite small and hard to read. But the levels are controlled by a rocker switch on one side in %. You'll likely find that 80% is good for a lav on the groom, maybe a bit higher if you are relying on it picking up the celebrant a few feet away as well. 90% if you have an H1 hidden a few feet away using its own mics. Around 20% in a loud disco. Auto-levels works well if there is consistently some sound. But it can be a pain if there are silences for several seconds as it will mess about noticeably with the gain in those silent moments. However the results will still be more than usable for the purpose.

With weddings its all about the emotion that you capture. The technical chops is much less important.

Pete
 
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