Compressors are one of the essential tools for sound engineers to control an audio signal's dynamic range. If we talk about Audio Compression, there are several types of compressors available, out of which, today, we will be talking about Optical Compressors. These compressors have become a popular choice among professionals, thanks to their several advantages. So, today we will be taking a closer look at Optical Compressors.
To begin with, an Optical Compressor is another audio compressor type that uses a light source and a photoresistor to control the gain reduction of an incoming audio signal.
When the audio signal passes through the compressor, the light source will illuminate the photoresistor, reducing the signal's gain. The technical part is that the amount of gain reduction varies based on the light it receives from the photoconductive cell.
The compressed sound is smooth and transparent, with a natural-sounding decay and release time. Apart from this, optically compressed sounds usually lack any distortion or any form of artefacts and even add a certain warmth and depth to the sound. The advantages and disadvantages of using an Optical Compressor are explained in detail in the sections below.
One of the most sought-after qualities in any musical tool is its ability to produce transparent sound, which is why Optical Compressors are so popular among technicians.
Transparent sound with no distortion and artefact makes them an ideal candidate for use with acoustic instruments like guitar, piano, and violin, as well as with vocals, where retaining the natural vibe of the performance is extremely crucial.
Another reason sound engineers prefer Optical Compressors over other types of audio compressors is its ability to glue a mix together, which is critical if you are mixing multiple elements in a track together.
If you want to make a music track sound good, one of the most important things is to ensure that it is cohesive and comes out naturally.
While controlling the dynamic range of an audio signal, most audio compressors mess up the naturality, so having a smooth compression that is gentle on transients will significantly help you maintain the natural tone of your tracks. Because Optical Compressors use sensitive photoresistors, they are effective in doing so.
In an optical compressor, the audio signal is attenuated by an optical attenuator consisting of an LED and a photoresistor. Because of these optoelectronic components, the Optical Compressor produces a relatively noise-free audio output with a low noise floor, even with low-level signals.
While there are many advantages to using an optical compressor, there are also a few disadvantages to consider:
Drawing from our personal experience, we have seen that when rookie music producers start using Optical Compressors, technicians realize that although an Optical Compressor has many benefits, they will not be able to have superior control to get the desired output. With limited control, many sound engineers do not prefer Optical Compressors because of the limited ability it gives to fine-tune the compression characteristics.
It is a known fact that Optical Compressors have a slower attack time than most types of compressors available in the market. This inability of providing a fast attack time makes them less suitable for certain applications where a fast transient response is critical to produce the desired effect.
Headroom is the amount of available gain that a piece of audio equipment has before the audio signal distorts or clips. Based on our firsthand experience, we can say that when it comes to Optical Compressors, they have a relatively limited amount of headroom compared to other types of audio compressors.
This happens because the optoelectronic component of the compressor has a limited range of gain reduction. Meanwhile, other audio compressors like the FET or VCA Compressors can achieve much higher gain reduction levels without distortion or clipping.
This is no new news that Optical Compressors are one of the most expensive equipment in a studio. While the cost of an Optical Compressor is justified because of the presence of optoelectronic components in it, which are generally expensive.
If you are serious about your work, you will have to invest in good equipment, and when that equipment is an Optical Compressor, you should consider all the factors so that you only have the best one for your needs.
As obvious as it can get, Budget is the most important factor before going ahead in the process of buying an Optical Compressor. Talking from our years of experience, we can say that Optical Compressors can range in price from a few hundred dollars to several thousand dollars.
So, decide how much of your hard-earned money you will shell out on audio compression equipment. Compressors are critical in producing professional-quality music and are a one-time buy.
If you have been working in the music industry for a while, you must have realized what your forte is. Although most of us work with anything we can handle, there is always a favorite.
This is why when choosing an Optical Compressor, consider what type of music you want to create the most, as different types of music require different types of equipment. The results can even vary significantly depending on the compressor settings.
For example, we can broadly say that Optical Compressors with slow attack time work well for smoothing out ballad dynamics but might not be the right choice for a fast-paced music genre like Rock.
Another important factor you should be clear about is where you will use your Optical Compressor, mostly because it changes everything.
For example, some Optical Compressors are great for mastering, offering precise control over gain reduction and producing transparent sound. At the same time, Optical Compressors for live sound reinforcement must have fast attack and release times.
While this does not even need a mention, considering the features an Optical Compressor has to offer is important when making the purchase. The market offers many options, and when you start going through these devices, you will understand that some Optical Compressors can offer a wide range of features, from simple controls for adjusting threshold and ratio. At the same time, Optical Compressors provide more advanced features like sidechain filtering, parallel compression, and stereo linking.
Choosing the right device will depend mainly on what feature set you will use the most in the future, and it is a very personal choice, so thoroughly think about it!
Last but not least, while many so-called professionals would say that brands do not matter, drawing from our experience, we would say otherwise. Brands spend millions of their money, time, and effort on research and development for each product they manufacture which has helped them build their reputation.
So, if your budget supports it, we would always recommend you buy a branded product for Optical Compressors, as chances are that it will be of high quality and will stay reliable for years to come.
Based on our firsthand experience, we have curated a brief list of tips and tricks for rookie technicians that will start using Optical Compressors.
The most common mistake we have seen music producers make while using Optical Compressors is that they jump straight to using the equipment without tweaking the settings according to the required output.
Settings are something you can not learn from a manual. The only thing you can do is practice, make mistakes and learn from them to achieve the desired effect.
Sidechain Filtering is a technique that can make your work easy while taking the quality of your audio signal to another level, as it allows for detecting only specific frequency ranges in the audio signal. This means that the compressor will only be triggered when the specified frequency level exceeds the set threshold and will not be affected by other frequencies in the signal.
Optical Compressors work terrifically well to emphasize certain aspects of your audio signal.
For example, suppose a music producer wants to feel the attack of a snare drum sounds nice. In that case, he can use the compressor to ascertain a certain emphasis on it by tweaking certain settings, allowing you to create a more focused and punchy sound.
Gain staging in sound engineering refers to setting levels and gain of the audio signal such that it is optimized to have a good signal-to-noise ratio and minimize the produced distortion in the audio.
When working with Optical Compressors, gain staging is important because, as we discussed earlier, Optical Compressors have limited headroom, so if the input signal to the compressor is too high, it can cause the compressor to clip and distort the signal. In contrast, if the signal is too low, it may not trigger the compressor in the first place, and the user will end up with an uncompressed audio output.
One tip we give every sound professional we meet is to mind how much compression they do on an audio signal. It is important to remember that audio compression is just one of the many tools one can use to enhance the quality of their music.
While Optical Compressors are great for doing many things, overusing them can do more harm than good to your music, as too much compression often results in a track that will sound lifeless and artificial.
After everything we have discussed today, we can conclude that Optical Compressors is a powerful tool that sound professionals can use for several purposes. Optical Compressors are popular as they produce a transparent, subtle compression that will enhance your music if used effectively.
If you don’t already own an Optical Compressor, we have also discussed all the factors you should consider before getting your first compressor.