Topic: Using Limiter

[santiam]

I’m a novice using a Tascam DR-07.  I’m going to be taping this weekend at a large outdoor festival with lots of crowd noise.  Could someone please explain to me how the limiter function works and how to use it?

I’ve read the manual, but it’s still a little unclear to me.  For loud concerts, is it better to use the limiter or peak reduction?  Or should I just try to set the levels manually?

[dallman]

You may get many answers, but personally I have never found a limiter to work effectively. There are many safe way around it. I record in 24 bit, at 24/48, and especially when I am getting "to know" a recorder, I am conservative in setting my levels. I try to have it virtually never peak. When I am done recording I use my computer and that is where I raise the volume level of my recording. There is no loss in recording quality at 24 bit if I record conservatively. There are many programs some free like audacity that will allow you to boost your volume levels and track your songs if so desired. After any corrections or changes, I "dither" the file down to a typical 16/44.1 wave file. Again there are programs for free like R8Brain that make this conversion quick and easy.

Of course the best thing you can do is find a live show or live event or some great loud noise where you can practice and get a feel for the deck. Good luck!

[eman]

A limiter could conceiveably be useful to pull down the peaks of nearby applause and yelling (if it is much louder than the music), but this can be done in post processing using limiter compression very easily and with minimal effect on the music. You will be able to set the dB level where the limit kicks in based on how loud the music can be seen to be, and thereby leave the music mostly alone while bringing down the peaks to the level of the music. You just need to make sure the audience noise does not peak the recorder during recording. Remove the audience peaks in post, then normalize. With a limiter, you are blindly adding an unknown amount of compression with no idea if you are affecting the music or if you could add more without affecting the music.

Audience to music ratio is why you have tapers getting up as close as they can. If the music is much louder than the audience, you are golden. You could try "stack recording"- getting in front of the speakers where the music is much louder, but without any appreciable stereo information, or try to find the "sweet spot" where the best results are achieved. If you record from far away, you lose detail in the music and the idiots around you become the focus of the recording. You can't polish this turd.

[earmonger]

You should always, always set levels manually.

The ideal is to make sure the loudest sounds at the show don't overload the recorder.  Unlike analog recording, when you wanted to get as hot a signal as you could without overloading, you have more leeway with digital because you can boost it later. So if your music peaks at -6 or even -12 db, it's no big deal.

The best way to test this is with a disposable opening act--make sure the peak is well below the maximum. And then dial it back a little more because the headliner gets to be even louder.

If you have Auto Levels they will wreck the dynamics of the music.

I just looked at the DR-07 manual and you're right, it is confusing.  If I understand it right, Peak Reduction works throughout the recording like a variation of Auto Level--you don't want that--while Limiter just kicks in with sudden loud sounds, kind of like an airbag.  So if you have somebody standing next to you who whoops like a train whistle at the end of every song, right next to your mic, Limiter might catch him.

As you will see, there are some almost theological preferences here about this.  Some people say Never Ever, some people say it's last-ditch insurance.  Personally, I use the Limiter on my recorder, a Sony PCM-10--and hope that it never has to kick in, because I have the music peaking at around -6db. But choose the right levels and it won't matter.

And as noted above, the less audience noise you get in the first place the better. Except for the whoopers and whistlers, Limiter really isn't going to help or hinder much either way.

[cashandkerouac]

unless you're familiar with the limiter and how it will effect the master recording i also vote for no limiter.  i've come to this conclusion after my own personal experiementation with limiters.  i certainly don't think they are horrible, but unless there is a really good reason why you have to use one for the master recording you can deal with excessive peaks in post-production quite effectively. 

[NOLAfishwater]

I always set my levels manually but engage the limiter on all channels just in case. Especially when recording 8 channels. Nice to have a little piece of mind just in case the sound guy is snoozing.

[DSatz]

I see that no one has actually told you what a limiter is, and that there's some confusion between a limiter and automatic level control.

A limiter is a circuit which very quickly reduces its gain (amplification factor) if a signal with a high peak level (above some defined threshold) comes along. It's like turning down the volume control on an amplifier the moment you hear something blasting through the speakers when you didn't intend to play anything so loudly--except that it's a circuit that's turning down the volume, it does it within a few milliseconds, and then if the incoming signal level goes back down again, a limiter quickly "releases" its limiting action. It's as if you turned the volume control on the amplifier back up to where it had been set initially, as soon as the loud music was finished.

What makes limiters different from automatic level controls is that limiters return the gain to normal rather quickly when no more signals are above their threshold. Automatic level controls, on the other hand, keep the gain at the reduced setting for a relatively long time--possibly for as long as you continue recording. (And on the third hand there are circuits called compressors, which do essentially what limiters do except that their initial response times and their release times are distinctly slower/longer.)

Some engineers use limiting as a kind of special effect or a way to make a recording seem "louder," but for your purposes and mine, limiters exist to prevent distortion due to overload. Used sparingly, a limiter can be a good safety net in case you underestimated how loud a show was going to get. But keep in mind that their net effect is to bring the most intense moments in whatever you're recording down toward the average level, so they detract from the naturalness and liveliness of sound when they're used more than a little. Extreme overuse of a limiter causes a garbled, highly artificial sound.

--best regards

[datbrad]

Also worth pointing out that there is a big difference between analog limiters on outboard mic preamps and mixers and digital limiters found on most small flash recorders in terms of performance. Analog limiters kick in to prevent mic preamps from clipping and introducing overload distortion to what they output. Digital limiters on recorders prevent the signal from peaking over a set value, but if there is distortion already from the mic preamps or active input circuits in the recorder being overloaded, the limiter won't help. Limiters on outboard preamps actually hold the signal to a few decibels below the overload point, and also can reduce the dynamic range of the output signal, all while delivering clean undisorted sound to the recorder.

[santiam]

Thanks for everyone's help.  I'm not that worried about sudden spikes in the music. 

I'm mostly worried about sudden screams and claps from the crowd around me.  I will be taping the Foo Fighters and Pearl Jam this weekend in Atlanta among a crowd of 30,000+.  I'll try to get as close as possible, but crowd noise will still be a huge factor.

I guess I will set my levels conservatively and hope for the best.  I have a lot to learn...  It's great to have a community of people who are so generous helping out newbies.  Thanks.

[bryonsos]

Good luck, and happy taping! Check this thread, you might find some advice regarding setting levels:

http://taperssection.com/index.php?topic=121672.msg1623322#msg1623322

[Gutbucket]

Also worth pointing out that there is a big difference between analog limiters on outboard mic preamps and mixers and digital limiters found on most small flash recorders in terms of performance. Analog limiters kick in to prevent mic preamps from clipping and introducing overload distortion to what they output. Digital limiters on recorders prevent the signal from peaking over a set value, but if there is distortion already from the mic preamps or active input circuits in the recorder being overloaded, the limiter won't help. Limiters on outboard preamps actually hold the signal to a few decibels below the overload point, and also can reduce the dynamic range of the output signal, all while delivering clean undisorted sound to the recorder.

I really don't understand why recorders have limiters at all which are implemented digitally after the analog input stage and ADC (which is most if not all small handhelds and most any mulitchannel recorder under $1000, exceptions are the more costly recorders with true analog limiters at the input stage such as Sound Devices, Nagra, possibly the more pro-oriented Tascam and Fostex gear, but not their small recorders including the DR-680 and Roland R-44).  Limiting at that stage does nothing to prevent overload, the signal has already passed through the entire analog chain and has been digitized.  Seems to be nothing more than a 'me too' marketing feature required to level the playing field between manufacturers for sales, yet completly worthless in actuality.  Am I missing something here?

[cashandkerouac]

since you had to lower your level on the M10 from "4" to "2.5" i suppose the signal from the pre into the recorder could have been too hot.  if that's the case your levels would look fine but you'd have audible clipping/distortion on the recording.  however, i have a feeling you've already thought of that scenario, so this suggestion may be of no value whatsoever. 

[kleiner Rainer]

Hi,

cell phone bursts (GSM) in one channel?

Greetings,

Rainer

[morst]

Thanks for everyone's help.  I'm not that worried about sudden spikes in the music. 

I'm mostly worried about sudden screams and claps from the crowd around me. ...

then LIMITER AHOY! Who cares if the crowd sounds are not as "natural" as the yahoo yelling next to you at the show, that helps a lot! And if the close clappers are less "lively" then you're doing yourself a favor by limiting their dynamics. DSatz once again comes through with a great response.

But keep in mind that their net effect is to bring the most intense moments in whatever you're recording down toward the average level, so they detract from the naturalness and liveliness of sound when they're used more than a little. Extreme overuse of a limiter causes a garbled, highly artificial sound.

Personally, I roll on my M10's with limiter ON, and then I run the level freaking hot. Works great. The limiter kicks on around -2 dB below 0dBfs, and flashes the red peak light. I had one recording where I ran with the limiter on, and even saw a few OVERs and a lot of red lights, and it never once peaked up to zero in the WAV file! The key for me is making sure it only kicks on for peak impulses like clapping, and drum hits, not sustained tones like bass guitar!