Soundtheory Gullfoss Standard by Diogo C
Thanks to digital technology and breakthroughs in computer power we have witnessed the arrival of audio processors that are far beyond what was possible ten years ago, and compared to the classic designs what we have in hands now would be easily described as science fiction material in the 1970s. Rising developer Soundtheory joins the high-tech ranks with Gullfoss, a plug-in that makes “intelligent” adjustments that are automatically and dynamically generated from the incoming signal — I’d describe its action as a unique form of dynamic equalization. In some ways it’s something similar in proposition to iZotope Neutron, Melda MAutoEqualizer and sonible smart:EQ plug-ins, although each of them have their own particular inner-workings and set of controls that sets one apart from the other. Gullfoss is perhaps simplest and straightforward to use of this current batch of forward-thinking EQs, it doesn’t boast a big feature list and there are only a few of parameters to play with, so it’s a rather minimalist plug-in. Let’s have a look at the available parameters:
- Recover and Tame: Perhaps the most important parameters on Gullfoss, recover and tame will deal with respectively “dominated” and “dominant” components of a signal. Recover emphasizes the dominated aspects while tame will counter dominant portions. In practice, we can verify that in general terms more energy equals dominant. For example, a monophonic synthesizer bass line can be quite a dominant element while ghost notes on a snare or other nuances can be entirely dominated on a busy mix.
- Bias: Determines the relationship between “recover” and “tame” for what Soundtheory calls “borderline cases”, situations where the plug-in has to decide which way to work. Positive values favouring more recovery. Inversely, negative values will give tame the precedence.
- Brighten: The most intuitive and self-explanatory parameter — turn it up for more high frequency content, turn it down if a “darker” sound with less top end is wanted.
- Boost: Raises low frequency whilst lowering the mid range. Alongside “brighten” it’s used for setting the frequency balance.
- Range limiters: two controls for high and low frequencies to determine the frequency range where the plug-in acts, which works in the same way as a sidechain and is highly useful as it allows the user to tackle only the desired areas.
- Gain: clean output gain with output level meter. There are also horizontal input and output level meters on the lower portion of the interface along with an action meter on the left side, so one can instantly visualize all the relevant information.
Gullfoss is an intelligent equalizer that listens to a signal and decides how to prepare the audio so that your brain can get the most information out of it. The real time analysis of Gullfoss uses Soundtheory’s computational auditory perception model to understand which audible elements are competing for your attention.The first part of the sentence above is something that I can wrap my head around as it describes the preliminary part of the process, but the second part is a bit mysterious, so let’s bring it to the real world. I’ve chosen three totally different situations to test Gullfoss:
First one was a synthesizer track with a percussive edge and lots of resonance coming out of a Moog DFAM. Gullfoss did a great job, taming the excessive high frequency content coming from the ladder filter inherently resonant character while also making the low end tighter and intelligible. Most importantly it sounds natural and not overly produced despite the busy action on the display, and I was very impressed with it. Could I solve this with my other plug-ins? Yes, I’d probably slap a dynamic EQ and get it done. Would it sound as good? Probably. Would it be so effortless? Definitely no. Gullfoss wins this one, and it’s a big victory.
Second test was a guitar bus on a death metal song. This bus consisted of two insanely distorted guitars as one expects from the genre, and Gullfoss ultimately failed to deliver any satisfactory results. It didn’t fix a resonance problem in the low end without making it sound overly bright and thin, which I countered by taking the low end out of the processing and by lowering the “brighten” parameter, but in this case my regular parametric EQ moves were more effective, and Gullfoss couldn’t do much against it. In this particular case running it prior to the EQ with subtle settings wielded the best results, but I’m also not sure if I need it in the first place, so I’ll take it as a draw.
Third and final test was on the stereo bus of a jazz project that I’m currently working on. It’s a simple project, with mixes that only have two recorded tracks for electric guitar and vocals alongside a return channel for the reverb send. I’m also the recording engineer for the project, so I’m taking extra care to capture it without thinking of “fixing it in the mixes” and so far it’s been a successful approach. There wasn’t much for Gullfoss to improve or fix here, so all it did was to make it sound “different”, not better or worse. And that’s another draw.
Out of three tries I had one excellent result and two which are somewhat inclusive, which confirmed my initial suspicion: Gullfoss can be used anywhere and just like most audio processors it doesn’t work all the time, but the major difference is that I can’t tell when to use it or if I should use it all the time. I know when to reach for a parametric EQ or multiband compressor, but I can’t really say when Gullfoss needed - or if I need it all the time! In the end we all want our tracks to sound “good”, but that’s something entirely subjective and that are based on our artistic views, so ultimately it’s up to each one to test these tools and draw their own conclusions. Nevertheless, Gullfoss is an intriguing processor and one worth exploring, it can solve problems that may be hard to deal with otherwise but right now I’m more inclined to recommend it for newcomers than for grizzled veterans.

The scores:
Sound quality: Gullfoss is mostly transparent, and depending on the settings you may not even notice that it is running, which indicates a very smooth processing that only leaves a footprint when pushed to extreme settings. It’s undeniably a good sounding plug-in that can work on certain situations, it won’t fix a bad song or make St. Anger’s snare sound good, but it can be a valuable tool for both the novice producer looking for an aid and the experienced engineer who wants to add a different approach to the age-old craft of improving sound quality. In my experience it worked best to re-balance busy tracks and crowded modern mixes where powerful elements are all competing for attention, and it was also good as a first line of treatment against weird resonant spikes and tonal imbalances, smoothing things out so they could be further processed with regular EQ and compression. The lasting impression is good, although only extended time will tell if stays or not in the chain.
Ease of use: The small number controls and clean interface makes Gullfoss quite easy to approach and also relatively easy to master. It shouldn’t take long before the user gets acquainted with the parameters but ultimately my experience with it was a bit of playing dice as it may or may not work on the program material. Having said that, I’ll look at the bright side and towards the best possible outcomes i.e. the plug-in improves the material, and when that happens the road to get there presents no obstacles, it’s really easy to use. Perhaps my only complaint is the small click area for the parameters, it’s not really a big issue but something that could be improved with a bigger font size along with a wider click area. In terms of performance Gullfoss runs relatively smoothly without overly taxing the computer, but it’s not a lightweight plug-in and adds some extra latency (1028 samples @ 48kHz), so keep that in mind when running big sessions with multiple instances of the plug-in - for what is worth my tests were all conducted on a MacBook Pro (15-inch/mid 2015) with Pro Tools 2018 and Mojave OS. Lastly, the documentation is quite concise but does a good job on explaining the core aspects and functionality of the plug-in, but I wouldn’t mind more in-depth material.
Features: Echoing the passage above, Gullfoss’ feature set may be minimal but it’s also very powerful, and each control plays a big role on determining the end results. The whole concept that drives the plug-in is very well-defined and focused, and the feature set is adequate and does its job of supporting it. It’s hard to ask for feature X or Y to be added in this context of this plug-in, it’s pretty tight and cohesive — on its own terms of course. I appreciate the bold approach of not including “vanilla” filters but on the other hand I think a dynamic parametric band would do wonder here.
Bang for buck: Gullfoss has price tag that is fair and in line with most of the EQ plug-in market, and if you find that it elevates your setup then it is totally worthy of the investment. Having said that, this is where things get a bit tricky. On one hand, I can see Gullfoss being a valuable tool to improve a certain track on a mix or a stereo bus on mixing or mastering situations. Slap it there, play with the parameters and something good may come out of it and that’s great if the end results are satisfactory. On the other hand, I can also see some shrugging it off entirely and dismissing it based on its rather unconventional approach. Those that are more attached to the rudiments and fundamental techniques of our craft may consider it too enigmatic and may find that it’s too much out of their hands. I must confess that I fall more on the second camp than on the first, thus I’m balancing my score accordingly, Nevertheless, I fully recommend reserving some time to properly evaluate it, and fortunately there’s full-working demo that last for two weeks so everyone can find out if Gullfoss works or not for them.