Today, we will take a deep dive into audio limiting plugins and hardware units to understand the concept, similarities, and differences. We’ll discuss free plugins up to the top-notch companies and their advanced functions.
After reading the article, you’ll be able to choose any suitable Limiter for your needs and understand how to use them the right way.
Hundreds of limiters are available on the market with the same goal: To prevent your Mixes and Masters from clipping while maintaining the sonics of your original Mix.
But why are there so many varieties for such a simple task? Let’s start with the basics and see how they are working.
The Basics: What Is A limiter?
A limiter is a compressor with high compression ratios, usually higher than 10:1 up to infinity. It analyses the input signal amplitude (volume) and smoothly attenuates peaks when the threshold breaches and cut them smoothly, avoiding artifacts like distortion & clicks.
This process allows you to increase the overall volume of your Mix and squeeze out a few dBs more. We have three basic controls that are on almost every Limiter: Threshold, Ceiling & Release.
Waves L2 limiter in action:
Setup the threshold when the Limiter should start limiting
Controls the output volume in dBFS
The time constant how fast it’s acting
That makes it the perfect mastering tool to increase the volume of your songs to a commercial standard and stay competitive.
Different Types Of Limiters
Another essential function is to prevent your speakers, ears, and equipment from damage by avoiding clipping. Therefore we have three different types of limiting:
- RMS Limiter
Get the maximum performance of your speakers while they prevent your speaker drives coils from burning.
- Clip Limiter
It prevents any signal from going over the ceiling (our set output volume) while cutting the transients aggressively. Watch out as this may distort your signal during the process.
- Peak Limiter
A Brickwall limiter that buffers the incoming signal. It looks ahead to turn down the peaks before they reach the actual unit.
Note: Only “True Peak” limiter prevents your audio from clipping, so chose this option if you can.
- Multiband Limiter
More flexibility by splitting the signal into multiple bands to apply limiting on problematic frequency ranges only.
The crossover frequencies allow us smooth transitions during the process so your track will still sound natural.
Additionally, we differentiate between:
- Usually, with a ratio of 10:1, peaks might come through.
- With ratios 10:1 and higher up to infinity, they prevent any audio from going over the ceiling.
What Is The Difference Between Limiting And Compression?
While compressors add color and glue to your elements, a limiter’s purpose is mainly technical. Though many compressors offer a limiting function, it’s not always desired to be the last part in your mastering chain as they are adding coloration to your final mix and do not always catch true peaks.
We will talk about coloring limiters in the next chapter and compare iZotope Maximizer vs. Vintage Limiter. Audio Professionals like Cameron Webb (Motorhead, NOFX) use compressors as a tone shaper instead of EQ and Limiter to control transients.
What Are The Side Effects When Limiting Too Much?
When limiting too much, you can get artifacts like clipping and distortion. Better listen carefully to the side effects when adjusting the threshold and ceiling in your mixes because these effects can make or break your track. As a rule of thumb, try to limit between -0.1 dBFS to -1.5dBFS in your Master Bus.
You can go even further in your mixes when catching peaks of percussive elements, up to -3 dBFs, or even more. This process allows you to increase the crest factor of your mixes and reach louder levels in the mastering phase. Take care that you don’t squash the life out of your mixes.
Difference Between Coloring And Transparent Limiter
- Colouring Limiter
Colouring plugins and hardware limiters will add tonal changes to your elements, which is not always desired. This effect has many reasons: Different transformers can change the tonality, the way they are built, and the quality of parts. Essential are wires quality, the way the coil is wound, and the type and size of the metalcore.
Another common way is to use a Tube Limiter like the famous Fairchild 670 and 660 built with 20 tubes. This makes it the perfect choice to use in your Mix to tame loud elements like drums, heavy guitars, or even gnarly bass tones to bring them further into the Mix.
- Transparent Limiter
Transparent Limiter doesn’t change the character of your Mix while performing their task. You’ll have a minimum amount of tolerable artifacts, which makes it the perfect mastering limiter.
The Xenon PSP limiter is one of the best on the market due to its enhanced features
What Limiter Should I Use?
Use a transparent limiter mainly for technical work to tame the peaks and make your Mix louder and a coloring limiter for tonal changes to beef up your mixes and masters. Your creativity is your limit(er) so feel free to test out different types in your next project.
Practice and experimentation will help you get comfortable with your toolbox and increase your workflow speed. It might be that the coloring limiter adds the last missing 5% in your Mix to make it perfect.
Software Limiter Plugin Examples
Many Limiters use the same functions but with different names. Learn the essential functions, and you will be able to work with any limiter plugin available on the market.
1. Waves L1, L2, And L3 Ultramaximizer
The Waves Limiter Series with the L1, L2, and L3 Ultramaximizer is perfect for beginners and easy to use. You set the threshold when limiting is desired and the output level with the ceiling. The Attenuation scale will show you the amount you are limiting – it’s that simple! Then you adjust the release time manually or keep it automatic.
- IDR Dither function
This is Waves’ unique algorithm for noise shaping to preserve your digitally processed audio’s resolution and sound quality.
The bit depth control allows us to choose the correct Bit depth for our track, for example, 16-bit for CD exports or 24-bit high resolution for online streaming and DVDs
- Dither noise shaping
We can choose between several noise shaping profiles which will be applied during the export phase to prevent intersample peaks. These can occur when changing the bit depth from the original audio (as recorded) to another format.
2. FabFilter Pro L2 Peak Limiter
The powerful, transparent FabFilter L2 Limiter works a bit differently but has the same effect. The Threshold function is missing and can be controlled with desired Output level instead. Adjust your input level that drives the Limiter, and you get the desired effect automatically. The Graphic indicator shows you the limiting amount.
- Adjustable look-ahead control
The look-ahead function buffers and analyses the incoming audio before it hits the brick wall limiter to predict the amount of limiting needed to avoid clipping.
- Adjustable Attack time
Compared to the previous Waves limiter, you have more control to adjust the attack time to taste.
- True peak limiting on/off
You can choose between true peak limiting to guarantee that no audio will exceed the setup threshold.
- Channel Link Transients
This function allows you to operate the Limiter in Stereo or Dual Mono mode. This is helpful when the left side of your track is louder than the right side. In Stereo mode, the Limiter compresses the whole song, while in Dual Mono, only the problematic side will be processed individually.
3. iZotope Ozone Maximizer And Vintage Limiter
The Ozone Maximizer is a transparent True Peak limiter with several limiting profiles to choose from, depending on the musical genre you are working with.
You have the essential functions like Threshold and Ceiling, while the release time is called “character.”
- IRC Limiting Profiles
iZotope created several profiles that change the reacting behavior when limiting your tracks. The differences are between attack/release time, the aggressiveness of limiting, and advanced modes using algorithms based on psychoacoustical bands. Those react to any incoming audio signal as intelligently as possible to push it to the maximum.
- Automatic “Learn Threshold” function
A useful function when you do mastering for streaming platforms. The threshold can be set to -14 LUFS and keeps your song in this loudness range to provide masters in the standard for Spotify, Deezer, Youtube, and more.
- Stereo independence
Control the processing amount between the individual left or right channel (Dual Mono) or Stereo independence, similar to the FabFilter L2 “Link” function.
- Transient Emphasis
This unique function helps you to preserve the punch in your songs after limiting is applied. Let’s take a rock song as an example where the snare would mainly trigger the Limiter, meaning the peaks get cut off and could smooth it out too much. The transient emphasis function can get the snare punch back on track.
- Advanced Dithering options
Remarkable are the meters, showing where exactly dithering (noise shaping) applied in the process.
The Ozone Vintage Limiter is a coloring limiter that can be ideally used in Mixing on individual elements.
It’s simpler than the Maximizer, and you have three coloring profiles:
This mode will emphasize your low-end transients with a fast attack time and add fat, old-school “smooth 60’s style” coloring to your final track
This mode emulates the non-linear characteristics of Tube hardware devices, so the tone shaping really depends on the input signal.
When using the modern function, you will simply get the best of both worlds as it operates as a hybrid with Analog and Tube characteristics. It will additionally use the modern IRC function for transient reproduction.
4. Oxford Limiter v3
One of the best True Peak Limiter plugins on the market is the transparent Oxford Limiter v3, with its simple interface and advanced functions. It’s divided into three sections:
The Input section serves to control the input volume as well as the threshold.
The Pre-Processing module allows you to adjust Attack & Release time and the Soft-Knee function to smooth the limiting amount.
The Output and Enhancement section contains the Output Trim that acts as the ceiling.
- Auto Gain
After the limiting stage, the auto gain will add the processed volume difference back to your track, so your masters will remain loud and proud.
- Enhance Curve
Oxford’s unique algorithm will preserve the original punch of your songs after the limiting stage. Helpful when heavy limiting is applied to prevent your songs from sounding dull and lifeless.
- Safe Mode
A switch to turn the True Peak limiter on and off. When turned on, the Enhance slider controls the amount of your perceived loudness.
5. Newfangled Audio – Elevate
The most innovative and unique of all Limiter is the Newfangled Audio Elevate plugin. A whole Mastering suite with intelligent functions and complex workflow.
You will find an overwhelming amount of buttons and options at the first look, but looking closer, you will find the three most essential features again: Threshold, Ceiling, and Speed (Release time). This Limiter has EVERYTHING you will ever need to achieve professional results, from the known True Peak on/off functions to transient emphasis and the flexible drive option to add color to your Mix. The Adaptive Gain and Speed will automate the limiting process with impressive results that makes the Mastering Engineers’ life easier than ever.
- 26 Linear Phase EQ (Filter Bank)
This intelligent function separates your audio into 26 Bands, emulating the process of how the human ear is perceiving audio. This process gives you the maximum flexibility to prevent artifacts like pumping, distortion and shaping your song the way you want.
- Additional EQ
The next Equalizer allows you to shape the sound of your song even after the last limiting stage. There is genuinely no other plugin that offers more flexibility.
- Match Level function
Another intelligent function matches the unprocessed track level to the processed one for effective A/B comparison. Our ears perceive frequencies differently depending on the volume of our tracks so that a louder track will sound fuller and sharper with more low and top end. Therefore this function helps us to hear if we gained any enhancements during the processing stage.
- Advanced monitoring options
- Mastering engineers need to know everything that happens to their track at every stage. You will find advanced metering options gives you 100% transparency throughout the entire process.
6. No 6 Limiter (Free Plugin)
No money, no problem! This free limiter “No 6” by Vladislav Goncharov gives you all the options you need to achieve professional master’s. This plugin processes audio in 5 stages: Compressor, Peak Limiter, HF Limiter, Clipper & Protection (Brick Wall) and is therefore pretty powerful for a free plugin.
- Mode switch
This plugin offers flexible processing that allows you to switch between Brickwall limiting, Soft mode to preserve transients, M/S mode & MultiBand compression/limiting. Multiband limiting comes in handy when you find problematic areas in the Mastering stage. One example would be a low crest factor (general low compression on the low end). Simply choose a frequency range from 0 – 100Hz and apply to limit on this range only.
- Mix Knob
This option allows you to blend the original signal in parallel with the processed signal, mainly used in compressors to add punch to your track. Go ahead and try it out when limiting; maybe you can discover some exciting and new ways to process audio.
7. T-Racks Quad Limiter
The T-Racks Quad Limiter is a flexible multi-band limiter, allowing you full control on the frequency spectrum that should be limited. A typical use case would be a perfectly balanced mix that peaks only when the snare hits. Now you can locate the mid-range band and apply a higher amount of limiting to tame the snare, avoid clipping and maintain the overall balance.
Best Hardware Limiter Examples
1. Teletronix LA-2A Optical Compressor/Limiter
The legendary Teletronix LA-2A Compressor/Limiter is probably the easiest to use with the least amount of functions. This compressor has a limiting function and two knobs that simply control the output gain as well as the threshold. Optical units work with a photocell and are known for slower reaction times. Therefore they are mainly used to color the track and tame the overall level, though true peaks can still come through.
You see, there are many additional features in every Limiter, but you’ll find most of them pretty quick on the second look. Threshold, Ceiling, Release are your best friends in limiting that gives you basically all you need.
If you are unsure about the additional functions, always check out the manual and try it again on your own mixes.
1. The Bettermaker Mastering Limiter
The Bettermaker Mastering Limiter has a helpful recall function, so you get a hardware unit with plugin features. You have complete control over adding color or having a clear signal path, as well as choosing between even and odd harmonics.
The release and attack control is adjustable and can be set to automatic if required, while the Threshold and Ceiling will be controlled via the input and output gain knobs.
- Soft/Hard clip switch
Depending on the song you are mixing, you can choose between hard/soft limiting of your tracks. Here’s a tip: Use hard clipping for ‘heavy’ genres like Rock, Punk, Metal, as well as HipHop and Trap music to add some ‘bite’ to your songs. The soft clip function is perfect for Folk, acoustic, classical & jazz genres to preserve the original character of the songs.
- Touch Screen
The touch screen is beneficial to recall previous settings and allows easy use of the Limiter.
- M/S operations possible
Allows you to process the Mid and Side signals independent from each other. This function can help to keep the low-end (in the Mid of your track) untouched while processing side elements like loud cymbals, background vocals, and more.
2. IGS Volfram Limiter
The IGS Volfram Limiter is inspired by the legendary 1176 compressor with additional functions, adding coloring distortion to your mixes. Don’t forget that increasing Release & Attack results in a slower reaction time.
- Sidechain High Pass Filter controls which frequency will trigger the limiter
- Dual Mono operations
3. Retro 176 Limiting Amplifier
The perfect tube-based hardware to reproduce the sound of the ’60s is the Retro 176 Limiting Amplifier. Set the compression ratio to 12:1, and it will act as a limiter at the end of your chain, coloring your mixes. Helpful features are two built-in bypass switches, one that allows reducing additional coloring bypassing the transformer while the hard-wired switch will bypass the whole unit for A/B testing.
Fast Attack And Release Time Vs. Slow Ones
Fast attack times will catch the transients on their peaks when entering the Limiter, while slower attack times catch rather the tail or won’t act at all. Here we go into tone shaping and control, how aggressive the Limiter will work on your track, what leads us to sound design.
Too fast attack times can choke your track and limit the life out of it; too slow attack times will make it unusable and let peaks through that can again clip or damage your audio equipment.
The release time determines how long the Limiter acts on transients.
I encourage you to make the following test:
- Add any limiter on your final Mix and play around with the attack and release time.
- Set the release time to the slowest level and push the threshold control down.
- Now observe the meter and listen to the effect.
How does it sound to you? Does your track still have the same dynamics?
Side Effects Of Heavy Limiting
Known side effects are “pumping” of your track, choking, distortion, and lack of dynamics. Another undesired effect is literally limiting the life out of your song and squash the dynamics. Effects like pumping are desired in genres like HipHop, EDM, so you have more freedom to experiment with these styles.
Undesired are the effects in genres like Jazz, clean Rock tracks, Blues, Country, and more. Distortion is simply heavily compressed audio, a side effect when cutting the transients aggressively. Therefore many limiters offer transient smoothing functions that will avoid clipping.
How To Use A Limiter In Mastering?
Add the Limiter at the end of your Mastering chain, monitor the input level, and make sure that you have at least -1 to -3 dBFS of headroom in your Mix. Set your ceiling to -0.1 dB, drag the threshold slider down, and test how much limiting can be applied before artifacts as distortion and clipping occur.
Put the threshold back to a normal level and listen closely to what is happening. Many limiters will show you the limiting amount and peaks visually; nevertheless, use your ears to avoid surprises.
Now you get a feel on how much you can squeeze out of your track and find the sweet spot.
When you hear a kind of pumping, the first step is adjusting the attack and release settings. If you desire to catch only the peaks, a fast attack and fast release setting will be your friend. When you like to add additional tone shaping, use a fast attack and slow release time.
If your Limiter should act as a safety because the Mix is already in good shape, use the fast attack and fast release time.
Optionally try out different coloring options (if available) and see if they are adding more beef and life to your track.
How To Use A Limiter In Mixing?
Limiting in Mixing can help to glue elements together, limit peaks on individual elements and get control of the dynamic range. This, in return, allows you to increase the volume of your mixes. You can control peaks from individual elements like vocals, bass, guitars, and especially drums. Add a limiter at the end of the chain and use a low threshold, fast attack and fast to middle release time.
It’s essential to keep the track alive so keep an eye on the gain reduction. One helpful tip is to use a coloring limiter on Rocking Bass guitars to bring consistent low end into the Mix.
Differences Between RMS, Clip, And True Peak Limiter
RMS represents the average volume of the waveform while the peak is the highest (loudest) point. The side effect in limiting is that the overall processing amount will differ and can therefore have undesired side effects. It’s possible that short peaks still come through when using an RMS limiter.
RMS Limiter will kick in and process the average loudness of your track, so peaks can still occur depending on your attack and release settings.
True Peak Limiter will work faster and prevent your tracks from clipping, as they work with the loudest point that occurs.
Check out this video if you want to know how the RMS value is calculated:
For more Infos, check out our article “Clipper vs. Limiter – The Differences, Purposes, and Mastering.”
Discovering Advanced Limiting Functions with PSP Xenon
While watching over 60+ hours of mastering tutorials, I saw many mastering engineers going for the PSP Xenon Limiter because of its advanced functions that make Mastering easy as cake.
Let’s check out all functions in-depth to help you understand more about the importance and complexity of the final stage in the audio engineering chain – Mastering. The 2 stage processing function is exceptional as the limiter analyses the audio and softens it before it goes into the second stage of Brick Wall limiting.
We can choose between three modes to chose the desired transient processing:
- Mode A
Hard Limiting (Clipper)
- Mode B
Medium Limiting with Look Ahead function
- Mode C
Soft Limiting with Look Ahead function
What Is The Look Ahead Function In Limiting?
The look-ahead function analyses incoming audio transients and predicts loud peaks before they arrive at the processor. It predicts how much gain reduction is needed to meet the desired output level and avoid clipping, making it the perfect option for clean “Brickwall” limiting.
We can control the envelope detector block settings with these options.
- II Order
Checks the incoming envelope and allows even lower aliasing
Limiter works in True-Peak mode
What Is Aliasing In Limiting?
Aliasing in audio are simply artifacts like distortion that can occur in the signal processor chain created during the sampling process. They mainly occur in bad conversions between sample rates, for example, downsampling from 48Khz to 44,1Khz when no dithering is engaged.
Attack, Release, And Input Gain Options
These are our good old friends to control the Attack and Release time as well as the Input Gain. Additionally, you can choose with the post meter function if the input gain knob impacts the audio before or after processing.
You have three graphs that simply show you the difference between Input gain, Gain reduction, and Output gain.
This Layout is straightforward to understand as you immediately see the effect when changing the settings.
For consistent loudness control, the meters operate in the K-System Mastering norm:
Mastering audio for broadcasting
Used for CD productions
For Movie productions
Both, RMS and peak levels, are measured, and they differ mainly between the amount of headroom and the crest factor.
Helpful for engineers worldwide to stay within the standard norms.
If you want to dig deep into Monitoring norms, check out these articles from Bob Katz.
Attenuation Section And Helpful Extras
Let’s go together through these surprising extra options:
Shows gain reduction from the Brickwall processing
Shows gain reduction applied by the leveler
Shows gain reduction from the first stage (Limiter)
Switch to a more precise metering scale
Switch between the following metering modes
Peak Limiter, K-12, K14 or K-20
Shows estimated inter-sample peaks in output meters
Pink noise generator to calibrate your speakers
Phew, this goes deep now, but that are all factors that a Mastering engineer considers.
Let’s jump into the last section to close this chapter.
Wordlength, Bypass & Link Functions
The Xenon Limiter comes with a configurable Word length reduction section. To keep the dynamic range close to the original, the Limiter applies its unique, high-quality dithering algorithm.
Turns the section on/off
Cuts dither noise in silent moments
Requantize your audio between 8, 12, 16, 20, and 24 bits
6 Additional noise shaping dithering options
We turn the limiter on/off with the Bypass knob.
The Link function allows us to use the Limiter in full stereo (100%) or Dual Mono, which means that the Left and Right channels are limited independently.
What Is The Leveler Function In The Xenon Limiter?
The Leveler allows us to compensate for possible volume changes throughout the song. This function helps us bring each part of dynamic songs as loud as possible and increase the perceived overall loudness, not the volume itself, as a psychoacoustic effect.
Keep in mind that there is a limit for the overall maximum loudness, and that is 0dBFS, so if you push the level anyway, artifacts occur, and we gain nothing at the end. The Leveler function helps us when we work with songs with an extensive dynamic range, with loud and low volume spots.
So when we set the Limiter for the quiet passages, artifacts might occur when the track comes to its full power in the chorus.
The Leveler function will save the day and slowly apply a constant gain reduction to your song before limiting is used to keep the procession consistent, allowing us to get the maximum volume out of our tracks while sounding natural.
Optionally you can turn off the function if “classical” limiting is desired.
I hope you learned something here and could discover something new for your daily workflow. We found that many limiters share the same basic functions and differ only in the workflow and name convention. With a little bit of training, you will master any limiter that crosses your way, and you know exactly how to use it.
Practice makes the master, so go out there, download the trials and discover all the differences on your own. Please share your experience and questions and feedback with us, and leave a comment below so that we all can learn from it. We will get back to you with an answer.
Adrian “Ady” Parzentny is a Musician, Mixing Engineer & Music Producer operating Hit The Road Music Studio. He is also a Music Production Teacher at Promix Academy with 17 tutorials, always looking for new ways to emphasize the core message and feel of the music. Sharing is caring and audio production is an adventurous, never-ending learning process.