High-Resolution Linear-Phase Split Compressor for VST-Compatible Audio Workstations
LP SplitComp is a creative dynamic tool with unparalleled transparency and sound purity combining the best of both the analog and digital worlds.
The split function allows dynamic processing only in the band of interest. Unlike many other split or multiband compressors the frequency crossover is made with low-noise linear-phase filters. They allow perfect band recombination after processing. The character of the PlugIn can be continuously adjusted between being more compressor or rather limiter. It provides a lot of psychoacoustically optimized features like automatic dynamic characteristics, soft knee, and parameterized soft clipper. To reduce the problem of alias frequencies being often a hidden problem in digital non-linear processors, a reference-quality oversampling has been implemented.
LP SplitComp is the second one in the new Algorithmix CHROMIUM SERIES, a set of reference mastering PlugIns. The current release is implemented as a stereo version, however it is intended to make it VST 3.0 compatible as soon as the major audio editing systems have switched to the new VST version. The compatibility to VST 3.0 will induce a multichannel version of the LP SplitComp.
Most fundamental but least understood
Dynamic processors, particularly compressors belong to the most fundamental tools in every recording, mixing or mastering studio. Despite the popularity and broadening of compressors they are probably the least understood and most misused processors in daily routine of the studio engineer. One reason might be that sonic changes of a good compressor are very subtle and hardly perceptible for an unexperienced listener. Another reason is the variety of parameters which differ from one unit to the other and even for the same parameter name exhibit a deviant behavior. The parameters are mostly interacting in some way and need a lot of experiments and understanding to learn how to use them in a purposeful manner.
A digitally implemented, well-designed mastering compressor has not necessarily less parameters, but they are precisely defined and de-coupled. In addition, due to novel, extraordinary possibilities of the digital signal processing, supported by psychoacoustic findings, digital compressors open a new quality window for mastering engineers.
Digital architecture with analog sound
The LP SplitComp arose from many years of experience of the Algorithmix audio algorithm architects, countless experiments, and critical sonic analysis of analog compressor legends. A serious, often unrecognized problem of nonlinear digital processors is a quite high amount of alias frequencies. They can ruin the best intentions spent for a good functionality. Therefore the audio path in our compressor has been equipped with a reference-quality oversampling to reduce unwanted alias frequencies.
Parallel compressing is known already for many years. It is accomplished by mixing the compressed signal with the direct signal in a mixing console. In digital technology it is extremely important to provide an exact delay alignment in the direct channel to avoid any unwanted signal cancellation because of phase differences. Therefore we implemented a properly time-aligned direct signal path. The Selective mode the LP SplitComp provides a new unique derivative of parallel compression.
Of course, the LP SplitComp can cut a good figure as a Full-Band compressor, but its true distinctiveness arises in the Split-Band mode. The signal is divided in two complementary parts: the first one is compressed and the second one is just passed through without dynamic changes. Due to the high-resolution linear-phase technology used for the implementation of the split filter, the reconstruction of the compressed and complementary band is performed completely without phase distortion contrary to some other split or multiband compressors. The concept of the LP SplitComp allow for very precise frequency-conscious dynamic processing. Especially if you need to “repair” specific spectral parts in dense mixes you will appreciate the surgical capabilities of this tool. Because of a noise-free design you can use this compressor repeatedly on the same material, each time concentrating on a particular dynamic task or problem.
Looking into the future
Because of using look-ahead delay in the signal path, the overs can be caught very precisely. Together with a respectively chosen attack time, numerous methods of transient treatment are possible. Using the Com/Lim feature you can make the processor more acting as a limiter or compressor. You can even use two instances of the LP SplitComp, the first one as a compressor and the second one as a limiter.
The side chain of the compressor includes a range of filters to make signal detection frequency dependent. The filters can be adjusted identical to the split filter bank to perfectly master frequency-selective tasks like de-essing or proximity effect removal. The static characteristic allows adjusting different grades of knee rounding (soft-knee) in order to make compression smoother, less obtrusive. A sophisticated release computer provides program-dependent reaction to any complex audio material.
A lot of helpful features
At the end of the signal path a soft clipper takes care that the output signal does not exceed the level adjusted in the Ceiling field. In addition it allows introducing some controlled distortions. To make the understanding and operation of the LP SplitComp as easy as possible we have implemented some additional features. The signal Monitoring is very comprehensive but yet intuitive. You can click on different nodes in the block diagram and thus listen to the relevant audio signals within the compressor architecture.
An additional feature, offered in a compressor only by Algorithmix, is the Differ function. It allows listening to the difference between input and output signal. So you can listen to the changes you’ve done to the signal in the PlugIn. This difference is possible solely because the whole path in the LP SplitComp is linear-phase.
You can also open a compact auxiliary Metering panel showing all level meters and indicators simultaneously and place it to any position of the screen.
You will love it
We believe, we have created a reference-quality compressor for mastering engineers that opens new ways in efficient, transparent and surgical dynamic processing. This compressor, however, is also intended as a creative tool for any other kind of computer audio processing in recording and mixing as well as in post-production, broadcast and TV studios.
Classic PEQ Blue
12-in-1. The most complete collection of classic equalizers ever in one DirectX / VST PlugIn: ten serial plus two parallel. Precise emulation of legendary analog equalizers, extended by progressive, new models: standard / vintage / modern / experimental. A sonic paradise for every recording and mixing engineer.
A few years ago we did not even think about spending our time to develop perhaps the 157th parametric equalizer on the market. Why one more? Is it possible to be noticed among all the other already established products?
It was you, our customers using our LinearPhase PEQ Red and Orange who asked Algorithmix to develop a classical recording/mixing equalizer but with its unparalleled purity and transparency. The biggest problem we had in the beginning was the equalizer style, so we closely analyzed many of them. To satisfy our customers as much as possible, we decided to implement not only one, but an entire collection of traditional (minimal-phase) equalizers. Most of them emulate analog archetypes; some are based on new ideas.
We hope you enjoy the dozen shades of Blue and find that favorite sound you previously could get only from very expensive outboard gear.
An engineer’s best friend
The equalizer is the oldest and the most popular sound processing tool. From the earliest days, its main function has been to correct or enhance sound by boosting or cutting certain frequency ranges. Engineers have developed countless equalizers for over 50 years. Some of them became legendary and were considered benchmarks--until now. The most popular version in recording and post-production studios is the parametric equalizer or PEQ. It offers maximal flexibility due to direct access to all relevant filter parameters. Properly used, the PEQ is a very powerful tool and the best friend of every sound engineer in the battle for perfect sound. If misused, it can be the greatest enemy of any recording.
The good, the bad and the ugly
In today’s era of digital audio workstations, hundreds of software parametric equalizers are available. Many of them are intended to be THE best sounding equalizer ever. The truth is that few of them are recognized and adored by the experts. You may ask why one equalizer sounds great while another does not. This question is almost as old as the equalizer itself and still is not completely answered. On the one hand there are some obvious rules which must be followed when designing a good sounding PEQ, on the other hand some esoteric claims driven by marketing departments or self-nominated audio evangelists, that never have really been proven. Especially treasured analog equalizers are considered by some people as being absolutely unique and unmatched by any ‘dirty’ digital equalizer. The truth is that with a properly designed, fully parametric analytic PEQ, every amplitude and phase characteristic of any other equalizer setup can be recreated. Of course, the contribution of distortions to the specific sound of a particular analog equalizer caused by the respective electronics has to be considered. If the distortions are ‘good’, they may make certain applications sound better. Usually, however, ‘bad’ non linear distortions and other deficiencies like limited dynamic range are surely not responsible for a ‘magic’ sound. Therefore our policy in PEQ design has always been to make the equalizer filters as precise and clean as possible. For controlled generation of distortions (if you really need any), we recommend using enhancers or any other specialized processors with proper built-in anti-aliasing technology.
The Blue Alchemy
After Algorithmix unveiled its linear-phase equalizers, the best mastering engineers certificated their unparalleled sound clarity and transparency, declaring them to be the new benchmark worldwide. At that time, our main intention was developing an equalizer for critical mastering and re-mastering tasks that could significantly boost or cut complex audio material without adding its own sound. After passing this difficult exam, our customers started asking us to develop a classic PEQ for recording and mixing, but with the world-famous Algorithmix purity and transparency. We knew that there has been no single particular PEQ style that could satisfy all the different flavors and habits in the audio community. Our intensive research and development efforts finally resulted in the Classic PEQ Blue, a parametric equalizer with 12 different faces. It contains the most complete collection of classic, vintage, modern and experimental equalizers ever included in one PlugIn. We hope that everybody will find his favorite PEQ characteristic depending on preferences and given applications. To avoid any conflict with trademark owners, we did not assign any real names to the PEQ types. Instead, we gave them rather neutral names related to their technical classification. You are invited to discover sound nuances and share with us your associations with real brands and/or products.
The most comprehensive collection of classic equalizers ever
Every PEQ type has 10 bands with five freely assignable parametric filter types including bell, low-shelf, high-shelf, low-cut, and high-cut. The most significant filters determining the equalizer name are bells. Set up to a certain Q, different bell filters change their bandwidth in a specific way depending on the boost or cut amount . To allow practical comparison between different equalizer types in the Classic PEQ Blue, the bells in all PEQs have been normalized to 6 dB boost, i.e., a separate bell looks identical for 6 dB boost and the same Q, independent of chosen PEQ type.
The Classic Symmetrical is the most popular bell shape used in many mixers and outboard equalizers. It is almost constant-Q. The three Proportional PEQs emulate bell characteristics which change their bandwidth proportionally to boost or cut. It is said that they behave more musically when used for recording and mixing; one does not need to correct Q after every amplitude correction. Furthermore, there are three other constant-Q equalizers with characteristics mostly used by some American brands. Algorithmix also offers two proprietary constant-Q characteristics. The first one, Constant-Q Ideal, is a perfect version of the Classic Symmetrical equalizer, having exactly the same bandwidth at any amplitude within Q definition range (i.e., measured 3 dB below maximum amplitude at and above + 6 dB boost). Such PEQs are impossible to implement in the analog domain. Similar curiosum is the Constant-Q New following a new interesting Q definition. It preserves exactly the same bandwidth at the half of the maximum amplitude; this for all adjustable amplitude values (including, unlike the classical Q definition, the range below 6 dB boost). Due to its amplitude/bandwidth dependency in terms of classical Q definition, this new kind of constant-Q PEQ could also be added to the proportional group.
Finally we emulated two vintage parallel equalizers. Unlike the serial parametric equalizer (almost all parametric PEQs are currently serial), parallel connected filters combine differently. They also behave differently in terms of phase. Their special problem with some interactive influences between bands is fully accepted due to compensation by a pleasant sound character. The Parallel LC emulates old parallel passive PEQ circuitry built with inductors and capacitors. The Parallel FF-FB emulates the feed-forward/feed-back structures still very popular in low-noise analog graphic equalizers. While the feed-forward path is trivial to implement, the feedback path is impossible to implement in traditional digital signal processing, because of the so-called delay-free feedback loops. In Classic PEQ Blue, we apply a very elaborate technique for true emulation of delay-free feedbacks for the first time to a commercial product. The result is a characteristic sound and perfectly complementary filters for boost and cut.
Shelf and Cut Filter Library
In Classic PEQ Blue, not only are various bell filters used but also different kinds of shelving filters. Nine of the serial equalizers use a new shelving filter generation characterized by cut-off frequency defined in the middle of the transition part. We found these filter definitions more intuitive than the classical ‘– 3 dB below maximum’. The old definition is only used in the Classic Asymmetrical type to conform to its original predecessor. All 2nd order shelving filters have a Q adjustment to emulate vintage characteristics with their specific bumps at higher slopes. Also, the parallel equalizers are equipped with respective shelving filters shapes being typical for the old parallel PEQs and interacting with other bands as did their analog predecessors.
Every complex PEQ is equipped with cut filters. In Classic PEQ Blue, each of the 12 equalizers can assign 1st and 2nd order cut filters. The 2nd order filters have a Q adjustment to create so-called resonant filters characteristics and very steep brickwall filters after cascading more of them (Butterworth, Bessel, Elliptic).
The best of the analog and digital worlds
Classic PEQ Blue is a creative equalizing tool combining the best of both the analog and digital worlds. We modeled the most legendary analog equalizers including two parallel ones and added a few experimental characteristics only possible in digital domain. To avoid bell filter asymmetry at high frequencies, typical for many digital equalizers, we have applied reference-quality upsampling techniques, automatically switchable if the sampling frequency of the input signal is 44.1 or 48 kHz. By using proprietary filter algorithms, we have achieved a huge dynamic range, as well as extremely low noise and distortion level and thus unparalleled sound purity--impossible with any analog circuitry. The whole equalizer collection works with sample rates up to 384 kHz and therefore is perfectly suitable for DSD post-processing. Several instances can be opened simultaneously. Complete setups can be easily exchanged between them. The true frequency response display is zoomable and in the DirectX version the whole PlugIn can be enlarged to the full screen.
LinearPhase PEQ Red
DirectX/VST 10-band precise linear-phase parametric equalizer featuring unique shelving filters for mastering of complex mixes without changing their sonic character
Every mastering engineer knows that equalization of final complex mixes or orchestral recordings with stereo microphones is very critical and limited.
Any correction of a single instrument or vocal part influences other instruments and can negatively change their sound characteristics. This is because all classic equalizers change the phase of the fundamentals and harmonics and the phase shift is frequency dependent.
The LinearPhase PEQ Red does not shift the phase. It only boosts or cuts the amplitude in a given frequency range. Consequently, you can apply much more boost without changing the sound character of your recording. Due our proprietary low-noise filter design in the frequency domain, the distortions (THD+N) are extremely low, ensuring crystal clear sound quality.
The LinearPhase PEQ Red DirectX/VST PlugIn is unique in the world of audio components. Almost all parametric equalizers being used are implemented with filters that accomplish phase shift, e.g.: the original signal is remixed with its phase-shifted version. Because the amount of the phase shift is frequency dependent some cancellation or amplification at certain desired frequencies takes place. It works, but with a major disadvantage--the different signal components are spread all over time, so that the time relationship between harmonics in the processed signal is heavily affected. The result is that a nice sharp bass drum becomes slurred and muddy, and vocal tracks become strident or brittle. Algorithmix is proud to offer you a true remedy against difficult equalizing tasks--the LinearPhase PEQ Red PlugIn, a linear-phase equalizer which can be handled exactly like its classic predecessors, but cannot be "heard".
Experts say that most of digital equalizers do not sound like their analog predecessors, especially when working with low sampling frequencies: 44.1 or 48kHz. Spectrum modifications in the high-frequency region sound as improperly balanced. The reason is so called frequency warping which makes the bells asymmetric and high shelving and high-cut filters much steeper as theoretically set up. To make the LinearPhase PEQ Red analog sounding, special corrections have been applied to the original digital filters making them look exactly like their analog references.
The LinearPhase PEQ Red features the Continuous Slope Filter™ technology, proprietary to Algorithmix and the only one of its kind, worldwide. Unusual flexible shelving and cut filters allow adjustment of any slope in the range from 0 to 24dB/octave.
The LinearPhase PEQ Red better preserves the time relationships of harmonics in the original waveform. This translates to smoother top end, sweeter and bigger midrange, and a clearer more distinct bottom end as compared with phase-shift EQ. The resultant sound seems less processed, more like it occurred naturally in the air in front of the microphone. The mixes become clear and transparent, the instruments more defined and "realistic". You can boost lower frequency regions by even 10dB without mud or slush and with no loss of transients at all. You can remove the sibilance from a vocal with a sharp notch without affecting the whole mix like occurs when using analog or IIR-based digital EQ.
The LinearPhase PEQ Red works in the frequency domain. It sounds a bit softer than his brother, LinearPhase PEQ Orange. It perfectly performs with up to 384kHz and allows extended frequency setup up to 80kHz. These features make it perfectly applicable for high-resolution DSD post-processing, inclusive the ultrasonic region.