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Elysia XFilter rack review in context of audio mastering

Elysia XFilter photo

Equalization is very important in mastering music, as such I have added another high end equalizer to the rack, extending tonal control possibilities. I present to you the Elysia XFilter rack.

Elysia is a German audio electronics and software developer most well known for their high end analogue audio designs. The XFilter is a 4 band “Class A stereo equalizer”. There are 1 set of controls for both the left and right channels, they are stereo ganged (linked) and detented so making accurate and recall-able equalization choices with this unit is easy. It is not a dual mono equalizer though of course you can run a mono signal through one channel should you wish. It’s strength is best served fairly obviously strapped across a set of stereo outputs on a sound card or wired to the insert points of an analogue mixing console or integrated within a mastering environment. Elysia employed computer testing to measure the tolerances of the pots used producing a typical match of within 0.1dB per channel. This is an excellent technical approach and has made this stereo equalizer very affordable relative to using switches that use discrete individually measured resistors. It has balanced XLR inputs and outputs.

The equalizer controls comprise 4 bands, a low shelf (20Hz to 900Hz) a low mid band (45Hz to 2.2kHz), with switchable narrow or wide Q (1.0) and (0.5) respectively, a high mid band (300Hz to 16kHz) with switchable narrow or wide Q and a high shelf (700Hz – 28kHz)

In addition the low and high shelf can be switched to act as low cut and high cut filters, an interesting touch adding flexibility. Another unique feature is that there is a single button which inserts a passive high end boost (a small resonant peak at 12kHz and an HF roll off at 17kHz as part of the slope design). Note : In the video demo I incorrectly described it as a shelf type filter button.

The equalizer has a bypass button which allows easy A/Bing of pre and post equalization which is a very important function for judging decisions.

All in all an interesting and flexible set of features for a 1u rack.

The XFilter in use:

Firstly the finely machined aluminium knobs detents are very smooth and positive. There is plenty of space between the knobs, making it very comfortable to use. The casing has vents at the side and is unusually made completely of aluminium. The unit comes in a lightweight 2kgs and has a dual voltage IEC mains electrical socket. At first I missed the absence of a 0dB setting on the band gains but you simply have to set them at 12 o’ clock and you are neutrally aligned. The “Hit it” button provides hard wire bypass a simple yet essential tool for making judgement on your sonic sculpting.

When you switch the equalizer on you are greeted with a series of very quiet relay clicks which presumably mute the outputs whilst the circuit is energized thus avoiding clicks and spikes from the audio outputs being sent onwards and ultimately to your monitoring. The equalizer is to all and intents and purposes noiseless.. no hum and no hiss.. exactly how we want a high end piece of audio equipment to be. Despite being Class A topology the unit remains nice and cool with only the slightest of warmth noticeable from the top panel.

The sound :

The equalizer acts quite predictably for an analogue unit and offers a clean and transparent pass through of audio. When testing an equalizer it is very easy to just boost. (as I did in the video)  This presents an essential set of unique characteristics and qualities from every eq but it is always worth cutting as well. Over all this equalizer is good value for hardware at its price point.. engineering quality and flexibility is great. I would say for a mastering studio it is a complementary equalizer to existing high quality choices. It would not be a good sole, first mastering eq though as it is not as flexible as one would like, especially in the low end.

When reading the following bear in mind that the sound is being judged on tonally complex  full bandwidth mix material and this is extremely challenging for any and all equalizers.

The lows:

In my own experience it is impossible for an equalizer for mastering duties to excel in every frequency band. The Manley Massive Passive gets close but still has some minor shortcomings meaning it does not work for all material all the time (and bear in mind the MP is almost 4 x the cost of the XFilter). The XFilter is no exception… in boost mode the low shelf sounds fine on acoustic material adding bass as expected. It can sound woolly in my own opinion on some thicker sounding material, rock and dance for example… not to say this could not work on some tracks.These low shelves are however going to be useful at cutting overblown bass issues from mixes. That is easily as important as boosting deficient material. The extreme lows however are very effective at adding low frequency sub bass heft and will definitely get use. It produces a very thick and yet tight sub-bass feel. I would not say this eq is a character piece.

Mid range :

The lower mids actually go down to 45Hz meaning they cover the bass range as well, here the boost situation fares much better as you can hone in more accurately with the parametric bell and having the flexibility of a more narrow Q choice if required. A very capable band for warming up the sound and reducing muddiness etc. Like any good analogue equalizer the Elysia sounds like it equalizes “in” the sound and not “on top of” like some digital eqs. This is why in professional mastering most reputable engineers use a combination of both digital and high end analogue eq.

A similar story for the high mids, sensible frequency choices will allow flexibility and common problems to be partially rectified with this eq alone. Again good overlap with the low mid band means this equalizer has been carefully thought about in terms of the jobs it will be able to handle.
The mid range bands are immediate and effective and you are likely to find fairly small boosts the order of the day for mastering full mix downs, as would be typical with an active equalizer circuit.

The high end :

The highs are useful on this equalizer, whether it is the complete absence of crossover distortion from the Class A circuits or the filter slopes themselves, smooth and detailed high end sheen can be added in 3 different ways (subject to material). You may wish to use the high mid band (bell) for sculpting the highs (8kHz- 12kHz -16kHz) with more care. Then apply the “Passive Massage” passive high boost filter button. Or you may opt for the fixed shape high shelf with 10kHz – 12kHz – 16kHz – 22kHz and 28kHz settings available. The overall sound of the top end is clean not coloured.

In addition the high and low shelves can be switch individually to low cut and high cut filters respectively (with resonant peak). They do exactly what you would expect them to in a fuss free manner. In mastering I would probably opt for an alternative choice for filtering the low end and whilst I could not immediately think of using the high cut it did sound very good so needs further experimentation on a case by case basis. I could imagine this being potentially useful with mixes that have excessive air presence.


This is a reasonable cost hardware eq, it is capable and quite flexible for the price.  It adds further tonal options and complements my existing custom equalizer and the Manley Massive Passive. I suspect as a sole unit in a mastering context it would need to be complemented by at least some digital based equalization (with respect to the relatively wide parametric bell Q’s) for tighter and more surgical tone corrections. Of note the X Filter is available in the API 500 series modular format for those who like this expandable system. It does not have the signal path euphonics of a high class tube and transformer based equalizer but it is of course significantly lower in price.

Always try to listen to any hardware before making a purchase to ensure it suits your specific needs.

By Barry Gardner