Lurssen Mastering EQ from IK Multimedia

IK Multimedia just released a brand new processor, the Lurssen Mastering EQ which is modelled on a famous (and expensive) tube-based analogue EQ unit. The original hardware EQ has been used at Lurssen Mastering by Gavin Lurssen and Reuben Cohen for years (they are multi Grammy-winning mastering engineers who have many gold and platinum records to their credit). And since working with IK Multimedia to develop the IK Multimedia Lurssen Mastering EQ, they have actually been using it on their mastering projects!



What is It?
The Lurssen Mastering EQ (LMEQ from now on) is a two channel mastering EQ that runs as a module in the stand-alone T-RackS 6 mastering console as seen below, or as a Plug-in for your DAW. Like its inspiration, it is not a full-parametric, surgical, precise by-the-numbers EQ. It is a very musical, tune-by-ear EQ. It has five bands: a low-shelf, three bell-shaped and a high-shelf. These are semi-parametric types, sometimes called 'sweepable' EQ, meaning they do not have user adjustable Q (bandwidth in case Q is not familiar). The knobs on the original hardware don’t even have a dB scale.



The original hardware included hand-made transformers, three per channel, and an LRC (inductor-resistor-capacitor) tone control circuit design with three valves/tubes per channel and even hand-wound inductors! It was as much a work of art as an engineering accomplishment. And it was, and is, famous in mastering circles. And to clarify matters, the hardware used by IK to create this mastering EQ is a unique unit owned by Lurssen mastering and modified over some years to perform as they specified. It was not a "stock" unit, as if anything hand-built with hand-made transformers and inductors could be considered stock.

The original specs indicate a maximum boost or cut of 12 dB, and LMEQ exceeds that by a few dB depending on which band is used and what adjacent bands are doing! I found maximum cuts ranged from -13 dB to -16 dB and boosts from +16 dB to +19 dB. The actual range and actual shape of boosts or cuts (see below) is affected by other bands, even when the other bands themselves use no cut or boost! This may sound like a defect, but is the way actual electronic circuits can behave, and is part of the famed warm, musical character and distinctive tonal colouration of the original hardware.


Above animation shows a cut at 240 Hz and a peak at 2 kHz shown for both LMEQ and a full parametric EQ – the two animated parametric curves use different levels of Q for the 2 kHz peak in an attempt to match the LMEQ curve, but it cannot be done. The skewed curves of LMEQ, as well as the interactions between bands are, no doubt, part of its musicality. BTW, I've never seen or heard of a mastering engineer using peaking gains of 16 dB – I cranked it up this high to more clearly see how LMEQ differs from "ordinary" minimum phase EQs.

Like the original, LMEQ has five pairs of band controls for each channel, a gain knob and a frequency control with from four to six selections. Yes, frequencies are fixed, not continuously variable. These ten controls were all the original hardware had, other than a power switch and a bypass switch for each channel. The available frequencies are a low shelf @ 20, 30, 60, and 100Hz, a low-mid bell @ 60,120,240, 500, 700Hz and 1kHz, a mid range bell @ 1.5k, 2k, 3k, 4k, and 5kHz, a high-mid bell @ 6k, 8k, 10k, 12k, and 16kHz, and a high shelf @ 3k, 5k, 10k, and 20kHz. These frequencies are “nominal” values and actual measured frequencies vary as much as 25% percent from these values depending on cut or boost levels! Very analogue.

BTW, LMEQ’s gain controls, like the real hardware, lack panel markings of dB settings. However, you can see a small window at the lower right of each knob that shows a digital readout, but this readout runs from -34 to +34 and has little to do with the actual dB gain or reduction being set! This is because, as I indicated earlier, the boost and cut ranges are not fixed, but vary from band to band and from the affects of other bands! Why they used +/- 34, I don’t know. But in use it is not a reading anyone is likely to use since LMEQ is a “set it by ear” EQ. In fact, I didn’t even notice these readouts for the first few hours I used LMEQ (I didn’t have a user manual).

Preamp Colouration
The original circuitry created saturation that varied with input signal level – LMEQ can provide saturation that is both input level dependent and further controllable with the Color control in the upper left of the front panel. If the Color control is turned off LMEQ can provide “clean” output, clear of any harmonics. If it is turned on and the variable knob above the purple Color button is set to its midpoint (which Gavin and Reuben indicate is the “sweet spot”) I found THD varied from slightly under 0.1% with peak-inputs near 0 dBFS down to about 0.01% with peak-inputs 24 dB below full scale. With the Color level control set to its maximum, these same signal levels created distortion levels from about 0.5% to about 0.03%. As you can see, LMEQ creates rather low levels of distortion even with the highest Color setting.

The harmonic balance also varies with the Color control setting and signal levels, with third and fifth harmonics dominant at the low end of signal levels and setting, and second harmonic becoming the dominant factor from the mid to high settings. Again, this is subtle distortion. These levels will not make a clean guitar sound distorted!

Some More Features
If you haven’t figured by now, mastering is a refined art and a look at the factory presets with examples from Gavin and Reuben finds mild settings, never exceeding +/-1 dB, and changes for different presets sometimes changing only a tenth of a dB! To help a user make fine adjustments you can press the Shift key before clicking on a gain knob and will be able to make changes as small as 0.01 dB! Speaking of presets, there are seven presets from each of the Lurssen Mastering engineers, and you can of course save your own.



LMEQ can link controls of the left and right channel, and it can also operate in mid-side mode providing separate EQ settings and separate gain levels of the mid and side signals, and of course converting the signals back to left/right signals as they leave LMEQ. DAW automation is available for every control (except RESET, but when would anyone want to automate that?), there is redo/undo, and the A/B/C/D comparison as IK have been supplying the past few years, rather than just A/B.

How Does It Sound?
Very musical! After a few hours using LMEQ on both commercial tracks and my own productions I was impressed with how truly musical the corrections were. I tried boosting the low end of some songs 6-8 dB and more, and the results were punchy without smearing of the bass, very pleasant. High frequency boosts also stayed “smooth”, not sure how to really say it. I didn’t find any setting that produced shrill frequencies.

LMEQ acts very “analogue-hardware-like” and operates much like I expect a physical EQ circuit to behave, well, without the actual hardware to grab. If you really want the rack mount hardware that LMEQ is modelled after, I see a used one for sale as I write this, at US$12,500. Would it sound better? I doubt the Lurssen team would think so – myself, I’d save my money for something else.

Technical
Available for Windows 10 and later as 64-bit VST 3 and AAX plug-ins. Requires Intel Core i5 Processor or equivalent, 8 GB of RAM and 9 GB of hard disk space. Requires an ASIO compatible sound card and an OpenGL 2 compatible graphics adapter.

Mac plug-ins available as 64-bit Audio Units, VST 3, and AAX. Requires Apple M1 or Intel® Core i5 Processor, 8 GB of RAM, 9 GB of hard drive space, an OpenGL 2 compatible graphics adapter and macOS® 10.15 or newer.

I tested the Lurssen Mastering EQ using a PC Audio Labs Rok Box with Intel Core i7-4770K CPU @ 3.5 GHz, 16 MB RAM. Tests were run in REAPER 7.34 and CPU load was surprisingly low at 0.3% per instance and I measured latency at a low 18 samples (a delay of 375 microseconds) at my preferred DAW sample rate of 48 kHz.

Pros
An excellent recreation of a highly desirable mastering EQ that Gavin Lurssen and Reuben Cohen find sonically as real as the original, but with very useful added features.

Unlike the real hardware you can save and recall all settings, even gains to the nearest hundredth of a dB if you are super critical – the original hardware is strictly manually controlled, with unmarked gain controls.

DAW automation of all controls (except RESET which I don’t know why anyone would want to automate).

Minimum phase design delivers the kind of phase shift that produces pleasing musical colouration like you’ve heard on countless rock/pop classics from the 60’s, 70’s, and 80’s.

Extremely low latency and very low CPU load if you want to use multiple instances on buses or tracks.

Reasonable price – list price is about 1% of the current used hardware price and the intro price is even lower.

Cons
Really? If you are looking for a really characterful, full-parametric EQ, this is not the box you are looking for. It is a faithful recreation of a mastering EQ known for it’s smooth, musical results. It may not be what you need if all you want is a functional EQ for use on tracks and buses, or if you think linear-phase EQs are better than minimum-phase designs (they are not).

https://www.ikmultimedia.com/product...enmasteringeq/