SPLEX User Manual
Contents
1. filters are Linkwitz Riley filters where each crossover is a cascade of a pair of Butterworth filters which ensures complementarity The overall rolloff is controlled by the order of the Butterworth filters LR2 uses first order Butterworths for 12 dB octave rolloff LR4 uses second order Butterworths for 24 dB octave rolloff and LR8 uses fourth order Butterworths for 48 dB octave rolloff For numerical stability the fourth order Butterworth filters are themselves digitally rendered as cascaded pairs of second order filters SPLEX User Manual Document Version 1 1 1dv2 9 C MIDI CHANNEL REMOTE ASSIGNMENT B Compressor Sharpness 15 output dB relative to threshold 5 0 5 10 input dB relative to threshold Figure 7 Black compressor response for maximum sharpness Red compressor re sponse for minimum sharpness called soft knee in other devices Compressors normally do nothing have a gain of unity until the signal exceeds the threshold and then reduce the gain for everything above threshold So a plot of out put gain vs input gain looks like the black line in Figure B However especially for large amounts of compression expansion it is nice to round out the transition so that it looks like the red curve in Figure B This is what is controlled by SPLEX s sharpness knobs C MIDI Channel Remote Assignment MIDI CC Remote short name Full name 12 freq1 lo mid frequency 13 freq2 mid hi f2. SPLEX User Manual SPLEX version 1 1 1 CONTENTS 1 OVERVIEW Contents 2 2 Crossover Filters 3 Compressor Expande 4 N Contool TRITATE ees 4 aug eee rrr 6 Pr 6 4 Internal Signal Path 6 Advanced Tricks 7 1 More Bands sissi ire X OX OR Re SUR a a 7 2 Breakouts and latency compensation 8 3 Controlling excessive sidechain pumping clicking 8 A Filter Details 9 B Compressor Sharpness 10 MIDI Channel Remote Assignment 10 1 Overview SPLEX is a multiband compressor which means it separates the input audio signal into different frequency bands then applies dynamic range compression usually with differ ent settings to each band individually SPLEX in particular has three frequency bands called lo mid and hi and features compressors that can also be used as expanders to increase rather than reduce the dynamic range Multiband compressors are usually used as a mastering tool late in the signal chain as an insert in the Master section in Reason for example but can be placed anywhere you d find frequency specific compression useful SPLEX can also be used without com pression as a crossover filter where the signal is split into bands in such a way that the recombined signal is as close to the original as possible SPLEX User Manual Document Version 1 1 1dv2 2 CROSSOVER FILTERS Figure 1 Front panel Figure 1 shows t
3. ble soft transition controlled by the sharpness knob that fades in the action of compression expansion from below threshold to above it Adjustable controls are from left to right SPLEX User Manual Document Version 1 1 1dv2 4 3 1 Controls 3 COMPRESSOR EXPANDER Figure 4 Compression section for a single band Compression ratio turning the dial to left of center will give compression ratios less than one in other words expansion The action of the compression expansion is indicated with the comp gain meter with compression going down from the center and expansion going up To save your ears the expander gain is limited to a maximum of 30 dB Sidechain ignore when an audio connection is made to the sidechain section of the back panel the sidechain active lamp switches on and the sidechain audio is used to control the compressor gain instead of the band filtered audio However you can switch back to using the band filtered audio using this button in which case the sidechain input is ignored Threshold sets the level above which compression expansion is applied How ever if the sharpness parameter is low some compression expansion will be ap plied even below threshold and not fully applied until well above threshold Sharpness without this feature the compressor wouldn t affect signals below threshold and fully compress signals above threshold A low sharpness however creates a soft
4. d you use the back panel to connect jumper the breakout out directly to the breakout in This will keep the timing of each frequency band aligned 5 3 Controlling excessive sidechain pumping clicking When using the sidechain inputs if the audio being used has very large and rapid changes in loudness like a kick drum then depending on compressor settings you may hear pumping or even clicking of the compressed audio This happens because the compressor is very rapidly switching from zero to full compression and back All sidechaining compressors can do this to some extent but there are a few ways to miti gate it e Use longer attack and release times This is ultimately the most effective way to eliminate clicking pumping SPLEX User Manual Document Version 1 1 1dv2 8 A FILTER DETAILS e Turn the sharpness down This may not eliminate clicks completely but it will smear out the transition from zero to full compression e Filter or compress the sidechain audio input Since the issue is caused by rapid changes in loudness a low pass filter or some compression can reduce these changes to a more manageable level A Filter Details For a crossover it is vitally important that the filters be complementary which means that when the outputs are recombined there should be no change at any frequency to the amplitude of the input signal For realtime filters that don t introduce a delay in the output this requires so
5. he front panel At the extreme left and right are sliders for input and output gain The inset left section controls the filter stage and the rest of the device has controls and indicators for the compressor stages Each frequency band has identical controls for its compressor Audio inputs and outputs are on the back panel shown in Figure 2 For many appli cations you ll only need the main inputs and outputs located to the left But if desired separate outputs are available for each frequency band at the far right and a breakout panel with the darker background allows you to pull the signal out and return it after the filters but before the compressors To the right of the breakout panel are sidechain inputs for each compressor and to the right of those are CV outputs for the gain of each compressor Figure 2 Back panel 2 Crossover Filters SPLEX has a three band crossover section though see section b for ways to gain more bands The two crossover frequencies lo to mid mid to hi are adjustable with the large knobs on the left of the front panel These are the center frequencies of the transition Rolloff of the filters is controlled by choosing the filtertype with the four position sliders Choices are e BSL this is a special filter type constructed with combinations of complementary Bessel filters specifically designed to guarantee thatthe recombined output signal is in phase with the input signal The tradeoff is that this fi
6. lter has a very slow and rather uneven rolloff But if you re absolutely set on preserving phase at all costs this is the filter for you SPLEX User Manual Document Version 1 1 1dv2 3 3 COMPRESSOR EXPANDER e LR2 is a Linkwitz Riley filter with a rolloff of 12 dB octave Linkwitz Riley filters are widely used amplitude matched crossovers that work nicely for a variety of applications The LR2 filter inverts the lowpass signal to bring the outputs back into phase e LR4 is a Linkwitz Riley filter with a rolloff of 24 dB octave e LR8 is a Linkwitz Riley filter with a rolloff of 48 dB octave Figure 3 Frequency section No set of filters is perfect experiment and find what works best for you Linkwitz Riley filters do somewhat affect the phase of the signal near the crossover frequencies This is generally completely inaudible unless you re using the SPLEX as a send effect mixing the SPLEX output back with the unfiltered signal In that case you may notice some notching at specific frequencies due to the filter stages especially with the LR8 filter If this is undesirable consider either using the BSL filter or sending the unfiltered signal through a second SPLEX with identical filter settings but bypassed compressors 3 Compressor Expander 3 1 Controls SPLEX contains three identical compression units one for each frequency band Each compressor can be used as an expander and each also has an adjusta
7. me compromise for SPLEX and most other crossovers this compromise is to allow small adjustments to the phase These are usually inaudible but SPLEX offers several filter choices to allow the user to find the best sound The separation into three bands is done in two stages each stage involving a pair of complementary low pass amp high pass filters for each stereo channel The first stage is the higher frequency filter so the input is split into the hi band and a mid lo band Then the second stage splits the latter into the mid and lo bands This order specifi cally ensures that the hi band where the ear is most sensitive is only filtered once and that the largest phase changes are concentrated in the lo band where they are least audible The BSL crossover is actually a composite It uses digital versions Bessel filters which have the smoothest phase response but Bessel low pass amp high pass filters are not complementary So the low pass or high pass of each stage is actually a mix of the Bessel low pass high pass filter and the complement of the high pass low pass filter This is done in such a way that the overall combination is complementary The trade off is that the already low roll off of the Bessel filter is increased and the rolloff is not completely smooth But the advantage is that the output is completely in phase with the input try mixing them back together and you ll see The LR
8. nput sockets Compressor Section sidechain inputs are used for setting compression amount if connected and sidechain ignore button is off Band Output sockets mixed into a single stereo audio pair Main Out gain adjustment Main Output sockets In particular note that the Main Out gain slider is only applied to the main output audio sockets and not the individual band output audio sockets Also note that using the breakout output sockets does not prevent audio from being sent through the rest of SPLEX However using the breakout input sockets will override any signal coming from the filter section SPLEX User Manual Document Version 1 1 1dv2 6 5 ADVANCED TRICKS 5 Advanced Tricks 5 1 More bands By chaining together two SPLEX units itis possible to create a five band unit For exam ple set the first SPLEX with a lo mid frequency of 60 Hz and a mid hi frequency of 8000 Hz The lo band output of this first SPLEX will contain frequencies from 0 60 Hz and the hi band from 8000 Hz Then route the mid band output into a second SPLEX with a lo mid frequency of 300 Hz and a mid hi frequency of 1600 Hz The lo band output of the second SPLEX will then contain frequencies from 60 300 Hz the mid band from 300 1600 Hz and the hi band from 1600 8000 Hz You can route this using the individual band outputs don t compress the mid band of the first SPLEX and patch the individual band outputs into a mixer for more contr
9. ol Or you can route it using the breakouts using the mid band breakout of the first SPLEX to go to the second then bringing the main output of the second SPLEX back to the mid band breakout input of the first SPLEX See the next section for a note on using the breakouts For an example of the wiring layout inside a Combinator unit see the following fig ures or download the Combi patch from the web site Figure 5 Front panel settings for five band compressor SPLEX User Manual Document Version 1 1 1dv2 7 5 2 Breakouts and latency compensation 5 ADVANCED TRICKS 5 BAND COMP z 4 E g 2 Figure 6 Rear panel wiring for five band compressor 5 2 Breakouts and latency compensation Reason is pretty smart about coping with feedback loops in device routing and using tiny delays to avoid infinite processing loops However it can t automatically know how to deal with situations where some channels of a device are looped but others are not Thus the recommendation is that if you use SPLEX s breakouts to apply other effects before returning to the SPLEX for compression then you should route each of the three channels in a similar way For example if you want to apply some extra pre compression distortion to the bass frequencies then go ahead and route the lo band through a Scream unit before return ing to the SPLEX However even if you don t wish to have any extra processing on the other frequencies it is recommende
10. requency 14 ftype1 lo mid filter type 15 ftype2 mid hi filter type 16 comp tra lo compressor ratio 17 comp 1th lo compressor threshold 18 comp1sh lo compressor sharpness SPLEX User Manual Document Version 1 1 1dv2 10 C MIDI CHANNEL REMOTE ASSIGNMENT 19 20 21 25 26 27 28 29 30 41 42 43 44 45 46 53 54 comp lat compire comp1ga comp1by comp1sl compisi comp2ra comp2th comp2sh comp2at comp2re comp2ga comp2by comp2sl comp2si comp3ra comp3th comp3sh comp3at comp3re comp3ga comp3by comp3sl comp3si inGain outGain lo compressor attack lo compressor release lo compressor gain lo compressor bypass lo compressor solo lo compressor sidechain ignore mid compressor ratio mid compressor threshold mid compressor sharpness mid compressor attack mid compressor release mid compressor gain mid compressor bypass mid compressor solo mid compressor sidechain ignore hi compressor ratio hi compressor threshold hi compressor sharpness hi compressor attack hi compressor release hi compressor gain hi compressor bypass hi compressor solo hi compressor sidechain ignore main input gain main output gain SPLEX User Manual Document Version 1 1 1dv2 11
11. top bottom with an adjustment to light the first lamp even for small values of gain The sidechain active lamps light as a reminder whenever a cable is connected to the sidechain inputs on the rear of the device When the light is lit the sidechain audio is being used to control compressor gain unless the sidechain ignore button is also on To the right of each compressor stage is another meter which shows the output audio level within each band before being mixed back together Meters are RMS averaged over 64 samples 3 3 CV Each band has a single CV output for the compressor gain This is a unipolar output which varies from zero when the compressor expander is inactive to one when the com pressor expander is at a gain expansion reduction of 20 dB 4 Internal Signal Path The overall signal path is quite linear with the input signal splitting into three bands after the crossover filters and mixing back into a stereo audio pair after the compres sor outputs Sidechain inputs are used only to set the compression level and otherwise do not affect the audio The breakouts allow you to divert the output signal after the crossover filters but before the compressors and allow you to return the signal or any other audio into the beginning of the compressor stages The specific order of opera tions is Main Input sockets Main In gain adjustment Filter Section splits into three bands Breakout Output sockets Breakout I
12. transition where some compression is applied even when the sig nal is a bit below threshold and the full compression doesn t take effect until a bit above threshold Attack how quickly the compression gain increases due to an increased signal level Setthisto a longer time to let through more punch from drums for example Release how quickly the compression gain decreases due to a decreased signal level Setthis to a longer time to smooth out pumping of the sound Band gain this changes the output gain of each band before they are mixed back together and output from either the main audio jacks or the band output jacks on the back panel Bypass this button bypasses the compressor stage for that specific band only Useful for auditioning whether the compressor is improving the sound especially in combination with the solo button Solo main activating any of these causes only the lit channels to be recombined and sent to the main audio output sockets They do not affect the individual band output audio sockets These are convenient to use when adjusting parameters to hear what s going on with a single band SPLEX User Manual Document Version 1 1 1dv2 5 3 2 Indicators 4 INTERNAL SIGNAL PATH 3 2 Indicators To the left of each compressor stage is a meter to indicate the gain reduction increase of each compressor expander The meters are scaled to display the gain in a range from 0 dB in the center to 20 dB at the
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