What do you understand about Limiters ?

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What do you understand about Limiters ?

Postby NativeAngels » 15 Jul 2019 20:59

On the Korg Arrangers Pa700 to Pa4x the is a Limiter on the Master Eq. I'm not quite sure what the different controls do.
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Re: What do you understand about Limiters ?

Postby Hugh-AR » 15 Jul 2019 22:30

The Limiter allows for an increased loudness of the MIDI tracks (Styles and Songs), by compressing the signal exceeding a defined threshold. MP3 files are not affected by the Limiter (since they are usually already "produced", and do not need to pass through the Limiter again).

The below is from the Korg User Manual.

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Hugh
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Re: What do you understand about Limiters ?

Postby Rev Tony Newnham » 16 Jul 2019 07:07

Hi

It looks like a case of sloppy terminology. A limiter is used to prevent signals exceeding a defined threshold - dynamics (i.e. soft & loud) remain intact until the threshold is reached, and then the signal just never goes any higher, so if the limiter is in constant operation, there are absolutely no dynamics (like a lot of music - especially pop broadcast these days as stations vie to be the loudest on the dial!). In the main, a limiter is a backstop in live recording, to deal with unexpected loud sounds, and is a protection device for radio transmitters, as funny things can happen if the signal exceeds the designed max. level. Not really of much use to a keyboard player. OTOH, a compressor reduces the dynamics of the audio above the threshold - for example, set to a 3:1 ratio, a 3dB increase in volume going in results in a 1dB increase at the output. It's normal for compressors to have "make up gain" so that the peak signal remains the same. The compressor used like this makes the music sound louder by reducing the dynamics at the louder end. Look up Compressor in books (or maybe web pages) about recording for a fuller explanation. The settings can make a vast difference to the resulting sound. Personally, for recording I don't like using a compressor, preferring the instrument's natural dynamics & volume range, but it does depend on the use of the recording. Background music needs to be at a fairly constant volume, whilst for serious listening, a wider dynamic range can be preferable.

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Re: What do you understand about Limiters ?

Postby Hugh-AR » 16 Jul 2019 09:49

Hi Tony,

Thanks. Got it! Reminds me of the first hearing aids I had, which were 'in the ear' moulded ones. I was playing my organ one day and put my foot down on the expression pedal as I wanted more volume at one particular point. The expression pedal didn't seem to be working as the volume remained the same. Tried a few chords and this time put my foot right down to the floor .. but the sound was no louder. So I rang my organ engineer and told him the expression pedal on my AR80 wasn't working.

He duly came round to sort it out, and repeated what I had done. "Sounds OK to me," he said. "There's plenty of volume when I put my foot right down to the floor. In fact, deafening, I would say."

And then the penny dropped. My hearing aids had a LIMITER on them. Soft sounds were soft, and got louder up to a certain point .. and then the LIMITER prevented the sound from getting any louder so my ear drums would not be damaged by excessive noise. Perfect for going to a disco, but not in the situation I was using them in. Removed my hearing aids and my organ sounded fine.

We both had a good laugh. And the engineer didn't charge me anything for calling round, which was very good of him.

Hugh

PS. I no longer have 'moulded' in the ear hearing aids and have normal ones with the microphone and amp sitting behind my ear. Although judging by the adverts from Hidden Hearing that appear in my paper every day, older people are going a bomb on 'in the ear' hearing aids because they don't want it known that they wear hearing aids! Frankly, I couldn't care less! What is important to me is that I hear things properly.
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Re: What do you understand about Limiters ?

Postby Hugh-AR » 16 Jul 2019 10:04

And while I am on this subject, I remember once (years ago) buying a Cassette Recorder to record the organ I had at the time (a Farfisa). What I hadn't realised when I bought it was that it had an 'Automatic Volume Control' that would keep the volume at the same level all the time. The tape recorder was designed to be taken to board meetings to record what was said, so if someone spoke quietly it would bring the volume up, and louder speakers would be made quieter.

No good for recording my organ then, as all the music came out 'flat' (meaning no expression .. not a change of key!).

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Re: What do you understand about Limiters ?

Postby NativeAngels » 16 Jul 2019 11:18

Thanks for that. As we know when most keyboards come out the box they have a flat sound or Eq settings.

You hear a few people say I just purchased Keyboard X and it doesn't sound like it did when it was being demonstrated.

Most arranger keyboards have some sort of master Eq and limiter / compressor but unless you know what they actually do it's like pin the tail on the donkey.

Then in other posts I read it's better to Eq each individual sound used in a registration.
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Re: What do you understand about Limiters ?

Postby NativeAngels » 17 Jul 2019 10:15

Here is a post from another forum on the Limiter

The Limiter in the PA700 is pretty useful. I use it on everything but have different settings based on what mode I am in on the PA700. I mostly use it to protect the internal speakers, since I do not always bring a PA system to the homes I play at.

For regular playing at the nursing homes, using the styles in the unit (like anything big band, etc..), I have a setting for that. I have found that some of the acoustic bass sounds tend to push the speakers a bit more than other bass sounds, especially in the key of 'G' where the acoustic bass produces a bass sound on the G2 note...that particular chord/bass note combination seems to flex the speakers a bit more physically than any other combination of chords or sounds on the PA700 for me.

I use the Limiter to minimize this because the Limiter is basically 'squashing' the signal at a certain threshold (or reducing) so that these peaks on that chord are minimized. I have sent my settings on that before, I believe. It should work.

The only problem is that when the overall output reaches that threshold, it squashes everything, not just the bass note. While it is not a problem for me, it is certainly something to think about when setting up the Limiter settings.

A Limiter and Compressor kind of do the same thing, but they go about it a little differently.

When I am in sequencer mode, I have another setting enabled so that more sound comes through the speakers without as much Limiting going on. I have found that when I use my Limiter settings designed for the Style Play in Sequencer mode, it sounds REALLY compressed (or limited) and it almost sounds unnatural. Think of compression/limiting used in radio stations versus listening to the actual CD containing the song that you are listening to on the radio; there is a marked difference.

When I am using the PA700 with an external PA and not using the volume settings/internal speakers above for monitor use (because I have external monitors or IEM's instead of using the internal speakers), I usually turn the Limiter off. This allows for the full range of sound from the PA700 to go to the PA system - unhindered.

In the manual, specifically starting on Page 488, it talks about the Master EQ/Limiter settings.

Basically:

The In/Out indicators are telling you what the signal looks like as it goes into the Limiter and as it comes out of the Limiter. If you are indeed limiting, then oftentimes (not using the Gain Adjust at all) the output signal will appear to be lower - this is because the Limiter is 'limiting' - like it is supposed to.

The Ratio is the amount of 'limiting' that you are doing. Increase the ratio, and the amount of limiting is increased. Limiting at 1:1 is not going to produce anything, because there is nothing being limited at a 1:1 ratio.

The Threshold is the setting that the limiting would take place. If you set the threshold at -10db, then any signal that tries to go above that will be limited. Anything under that threshold would not be affected.

The Attack is the speed of which the Limiter activates. If the Attack is set with a lower number, then the Limiter will activate more quickly. If the number is set higher, then it will activate more slowly.

The Release is the speed in which the Limiter will release the signal. The lower the number, the faster the Release would happen.

The Gain Adjust is basically like a 'make up' gain because limiting the signal will often reduce the output volume. This allows you to make the volume louder after it has been limited. What you are doing is turning up the 'Limited' volume so that it is louder, even though the 'limiting' has been in place. This Gain Adjust setting is similar to the output knob on a compressor.

My recommendation is to play with the settings and find one that works the best for you. I basically use the Limiter to protect the internal speakers.
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Re: What do you understand about Limiters ?

Postby kens » 17 Jul 2019 11:02

Is this what is called CLIPPING in Audacity? Ken S
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Re: What do you understand about Limiters ?

Postby Hugh-AR » 17 Jul 2019 18:57

Hi Ken,

Yes, sort of. In Audacity volume levels are 'as is' until they reach the maximum limit, and at that point the excess sound is not recorded ie. it is 'clipped'. Which means that when you play the recording back, that bit of the signal is missing, which makes what you are listening to distorted.

If Audacity had a LIMITER then it would prevent this happening. As soon as the maximum was exceeded it would keep all the signal below that maximum level and not 'clip' it. But this would also mean that all those top volumes would be the same.

In this age of 'digital' recording, the secret weapon Audacity has is a sort of LIMITER, but works in a different way. The idea is that you under record your piece .. so it gets nowhere near that maximum limit. In the old days of recording, using microphones and meters to see where your recording levels were, if you did that then the recording would play back with a low volume. So the recording engineer had to use his experience and skill to get as much volume into the recording as he could without exceeding that limit. If it didn't work out they would have to do the whole recording again with an 'adjusted' recording level.

The secret weapon Audacity has is to Normalise the recording after you have done it. This means to analyse the whole recording (which you have 'under recorded') and increases all the volumes in proportion, making the loudest sound just at or under that top limit. The top limit is 0 (zero), but you can get it to do it to -1 (just below the limit) or -2 etc. I normally do my recordings to -2. This 'limits' the recording to below that cut-off point, but in proportion to the original volumes. And this is the essence of it, to keep those volumes (loud and soft bits) in proportion without exceeding that limit. It makes recording so much easier to do these days.

Hugh
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