In this article, we will be checking out ACME Opticom XLA-3 and Brainworx bx_opto.
We will be reviewing the qualities and specifications of both plugins. Then, we will be comparing their tonal characteristic and what applications they are most suited for. We will do this by processing drums, a vocal track, and bass.
Both plugins emulate a method of compression that only optical compressors can deliver. While VCA and FET compressors have a really controlled attack and release time, optical compressors tend to have slower release times because of the nature of their built. Basically, the audio signal that goes into the compressor is transformed into light, which triggers a photosensitive cell that controls gain reduction. This photosensitive cell has a soft release curve, and it depends on how loud the signal is received. The more intense the light is, the longer the release time of the cell will be.
First, we will take a look at some of the parameters available on both plugins:
1. ACME Audio Opticom XLA-3
On a first look, we can notice that this plugin lacks a threshold dedicated knob; this is because it has an input gain into a fixed threshold.
To draw more compression, you just have to turn up this knob, the type of setup you could found in a Distressor, for example. You can turn down the input signal by -15db by double-clicking the gain knob.
The same goes for attack and release time: instead of having a dedicated knob, you get this response switch that can be set to Slow, Normal, and Fast. This switch adjusts by default both attack and release times.
From left to right, the first VU meter shows us input and output signal, letting us choose between those two with its dedicated switch. On the right side of the unit, we have the gain reduction indicator. You can notice that below these two are screws that can trim the output signal and also get a dry/wet balance of the signal.
The in-out-amp selector gives flexibility in terms of coloration. We can run the signal into the compressor, take it out of the way or use the amp mode to use the plugin only as an analog distortion stage.
There is another little screw that emulates noise floor for those seeking the device’s real feel.
2. Brainworx bx_opto
Differing from its competitor, bx_opto delivers a BIG peak reduction knob alongside an output knob to use as a make-up gain stage. Pretty standard.
Below that, we encounter the fun part of this compressor which is the speed time, the mix, and the sidechain. Tweaking these three together can result in a vast palette of sounds.
Adjusting the speed at a higher value will result in aggressive compression, squashing the signal without changing its primal tone. On the other hand, by setting its value close to zero, we get the classic, more transparent type of compression that opticals are known for. The use of this knob becomes crucial when it comes to shaping the transients of your signal.
The sidechain offers a sweepable filter from 20 Hz to 20 kHz, an Off-On-Solo switch, and a filter selector. Not only is this a good way to control the dynamics of your sound more accurately, but it also can be used as a dynamic equalizer.
The mix knob allows us to give the final touch to our sound by blending the compressed signal with the dry signal.
- Drums test
First, I tried to achieve a very smooth and transparent compression without coloring the signal. When I dropped both plugins in their respective channels and listened without tweaking any knobs (only matched the output level), I immediately heard the difference. It is clear that they have very distinctive sound qualities.
This is a sample of the drums’ dry signal.
Let’s take a look at the signal processed by ACME’s Opticom:
This is the drums signal processed with the same setup with a variation in the response switch only.
Although this plugin can deliver a lot of sonic options in spite of its limited controls, I wasn’t that keen on its softer side. You can notice that it lacks control if you are going for a neutral-sounding type of compression.
It certainly has a unique tonal characteristic that could work for a lot of applications, but it is up to you to decide if you like this color or not.
I’ve found myself enjoying the crunchy tone that is given when the response switch is set to Fast. Of course, you can make a more subtle coloration by setting it to Normal and crank up the gain knob a bit.
This is the setup I’ve used, only modifying its response control:
In spite of setting a low value of gain input, we still achieved a little bit of that saturation that it seems it’s the main characteristic of this compressor.
Now let’s take a look at how the bx_Opto dealt with this situation:
We can see that its 0% to 50% range is way softer than Opticom’s Slow to Normal. Still, at 100%, the bx_Opto could squash the signal but in a very delicate way. It remained transparent without adding a color of its own.
- This is the setup I’ve used to process the drums:
Notice that the peak reduction is set to 50%.
This plugin has a lot more control than its competitor. I got hooked with it once I’ve turned on the sidechain. Not only was I able to moderate the signal dynamics, but also I could shape its tonal characteristic like a dynamic equalizer. Although this drum track sounds great on its own, thanks to bx_opto, I could get rid of some muddy frequencies in the lower part of its spectrum without losing vital information about it.
The filter type selector allowed me to reinforce and control the sound with a level of specificity that I could not achieve with the Opticom. It kinda overwhelmed me as well, so if you get this, be prepared to get really critical on your listening. Thankfully, the plugin also provides an option where you can solo the band that you are about to process.
Blending a great compressed sound with the dry signal was super satisfying to me.
- Vocal Test
Once I’ve had an idea of how these plugins behave on drums, I’ve wanted to give it a try on vocals.
Maybe because I’m a drummer and I’m not that used to work with vocal tracks, I’ve found it harder to get a clear difference between the dry and wet signal on the bx_opto. Because of that, I’ve tried a couple of presets. When I used the “Lead Vocals Less S,” I confirmed once again the surgical characteristic of this plugin and its transparency.
- This is the setup I’ve used to compress the vocals in bx_opto:
The result was very pleasing to the ears, softly shaping the tonal characteristic of the vocals. It also gave me the opportunity to control certain frequencies that I’ve founded problematic.
On the other hand, I’ve found the Opticom compressor to be really good on vocals. In contrast to the drum processing, I encountered a warmer signal but not distorted. It achieved a full-bodied tone and still got the core characteristics of the dry signal. Still, I felt very limited in terms of options since the signature sound of the Opticom impregnates immediately on the processed signal. Again, this could be good or bad depending on your taste. Personally, I think it has a great tone to it, but don’t expect to have a wide array of options. Aggressive, yet musical.
- This is the setup I’ve used for vocals in Opticom:
Let’s check out the result of both processes:
This is a comparison between the dry vocal signal and the one processed with bx_opto.
This is a comparison between the dry vocal signal and the one processed with Opticom.
- Bass Test
I’ve used a bass take constituted by the amp tone and a DI. This combination gave me plenty of harmonics to work with.
- This is the setup I’ve used to compress the bass in Opticom:
The Opticom responded really well on this bass track, but I couldn’t find a sweet spot between transparency and aggressiveness. Its core tone is even more obvious in this kind of tracks, and by cranking up the input gain knob, you get this crunchy yet boomy feeling to it: both 100 Hz and 1000hz-1300hz areas were heavily boosted with its response set to Normal or Fast. I kinda liked the crunchiness given by the input knob, so I found a nice equilibrium when I turned the response switch to Slow. This gave me the opportunity to set a configuration where compression combined with distortion stood up.
I found this plugin to be a rock-punk-metal-oriented kind for bass since it can become uncontrollable. It could work really well on electronic basses.
Luckily, ACME provides the dry/wet mix control to get back some of the unprocessed feels to the signal.
This is the dry signal of the bass track.
This is the signal processed by Opticom. It can really squash the signal; keep in mind that it will come with heavy distortion and coloration too.
- This is the setup I’ve used to process the signal with bx_opto:
On the other hand, and as we’ve already seen, bx_opto won the battle when it comes to versatility. Although I could not reach a heavily distorted tone with it, I was able to manage the spectral information of the track with more precision. The key to making your bass track sit well in the mix is to set the sweepable filter correctly to boost/control the mid frequencies. Of course, it will depend on your material’s character, but I found it very useful, especially by bringing back some of the dry signal to define the attack.
When it comes to a bass track, I would use this plugin in a variety of genres and situations, especially in non-electronic ones, because of its sharp control. It can make a slap bass cut through the mix as well as get the right tone for the bassist who is used to play with picks.
This is the signal processed by the bx_opto.
Wich one is the best? If you are wondering that, I wouldn’t go for that question. Instead, I would ask myself, what do you need them for.
As I’ve stated before, ACME Audio Opticom is more than just an opto compressor. It delivers its own personal tone to the track you are processing, giving it crunchiness and attitude. What I found interesting about this is that it can respond very differently depending on your sound source. I absolutely loved the distortion added to the drums; it could be a must for a rock setting, for example. Also, I found it to be very effective and simple on the vocals, but I think it is a little bit limited since I couldn’t control the dynamics with the same precision I found in the bx_opto. It could be a great addition to your mix bus if you are looking for that extra analog distortion flavor.
If you are looking for a clean and precise compressor, this one is not for you. It does what it does, and don’t expect it to be a versatile one. However, I think it’s worth checking out since it can make some materials stand out and cut through the mix.
On the other hand, I found Brainworx bx_opto to be crystalline and precise. While with Opticom, you have to guess which frequencies of your sound are going to be processed, bx_opto lets you shape the tone of the output thanks to its dynamic processor. Knowing how to use the sidechain section with its sweepable filter and the mix knob properly can be a very powerful combination in terms of coloration. Also, you can apply very heavy compression to your signal and still manage to keep the main characteristics of your dry signal. This plugin is very flexible, but it can be hard to achieve good results for beginners or people who are not used to this kind of surgical compressor.
To sum up, I personally preferred Opticom’s personal character, but I’m aware that many users could not be so hooked with its tone. If you are looking for instant gratification, go for Opticom. If you want a flexible and transparent device to get the exact amount of compression you need, go for the bx_opto.
I’m a music producer, composer and drummer. I’m an Ableton Live trainer with expertise in electronic music and sound design. I’ve also studied electroacoustic music at Universidad Nacional de Quilmes.