Weiss DS5 Multiband Compressor

Introduction

We've been asked to make a multiband version of the Weiss DS1-MK3 ever since its release, and it's been a challenging project, both from a CPU perspective as well as from a user perspective. The original Weiss DS1-MK3 is a deep product with nearly endless possibilities, and five of them doesn't exactly reduce the possibilities.

The key is the macro controls and presets. The presets are starting points, designed to be tweaked. It's often possible to just lower the Threshold a bit to get where you want, while other times you might need to increase the Attack or re-balance the Make-Up Gains. The point is that most of the "advanced" controls have been set in the preset, and in many cases you just need the macro controls and front page to get where you want to.

But when you want to go deep, open up the Weiss DS1 by double-clicking on a band, and there you have all the options.

Weiss DS1-MK3 x 5

The DS5 is running five line-by-line code ports of the hardware DS1-MK3 in the background, one for each band. To make it fit into a normal computer (each hardware DS1 uses five Sharc DSPs) we removed parts that aren't used, like the DS1's internal cross-over filters, per band safety limiting, and other features. We kept the compressor core just like it is, with both compression and upwards expansion ratios!

Macro Controls with Tilt Function

To make it easier to control five DS1s, there are five main macro controls on the front panel. They control all DS1s in tandem.

The Tilt All Bands functionality makes it even faster to adjust the five bands, especially in the case where you know that the high bands need a different setting from the low bands. A typical use case is Attack and Release times, where it's often possible to use longer times for bands in the lower frequency ranges and still have a transparent and clean sound. Engage Tilt, either through the Tilt All Bands button or by pressing Shift while adjusting the macro, and see how the attack times "pivot" around their average value, making it easier to set longer times for lower bands.

Another very common use case is to adjust the Threshold for all bands quickly. Music tends to have more energy on the bass side, and the lower bands typically need a higher Threshold.

Large Visualizations

The large visualization makes it easy to see and adjust Threshold, Ratio and Make-Up, as well as see the current gain change of the band. Feel free to remove bands if five is too much (it usually is).

Phase Compensated Filters with Three Modes

The cross-over filters are phase compensated 24 dB/octave filters, that can be activated in three different modes. Dynamic Phase uses a minimum phase implementation, similar to that of a dynamic equalizer. Static Phase is a phase compensated crossover structure with a phase response that's independent of the gain change, and Linear Phase uses Weiss EQ1 technology to exchange the phase response with a static latency.

The main goal for the filter design is "transparency". The filters and the compression should be as transparent as possible. You will notice that it's more transparent to "scoop out" a large chunk of audio using the DS5, than for example using spectral techniques and resonance suppressors. Even if those appear to "only" change a small portion of the audio in the frequency domain, the narrowness will lead to time-domain (ringing) issues. The DS5 filters were designed to be fast, with pre- and post-ringing artifacts reduced to a mathematical minimum.

Freely Adjustable Side Chain Filters

Each band can use a completely independent detector filter, which can also be triggered using an external side chain. There are two simple tricks that use these features. First, if you have a dense stereo mix and a separate vocal track, it might be difficult to get the vocals to "sit" right with the stereo mix. Use the external side chain to have the vocals compress a band in the stereo mix, so that only the frequency range that the vocals are using are being attenuated whenever the vocal is playing.

With the freely adjustable detector filter, it's possible to have the higher frequencies attenuated (or enhanced) by triggering the high band with a low frequency detector. If you have a problematic kick drum in a stereo mix, you can trigger the high band from the kick's frequency range and letting the high band expand when the kick hits (that will make the kick more articulate), or compress the high band when the kick hits (which will make the kick sound bigger).

Mid/Side

Each band can be configured for stereo audio, or run as mid, side, left or right. A stereo side chain can be linked (same gain reduction in both channels), unlinked or anything in between.

Low Latency

The whole algorithm has been designed for low latency use, from the Dynamic and Static Phase modes to the newly designed safety limiter. But when latency isn't an issue, switch to the Linear Phase mode for pristine clean mastering compression, or add a bunch of lookahead using the Preview slider.

User Interface

The user interface consists of three parts:

1. The "Lower Area" with the macro knobs and global controls.

2. The "Upper Area" with main compression parameters (Cross-over Frequencies, Ratio, Threshold and Make-Up) as well as gain change visualizations.

3. The "Weiss DS1" expert panel with the full Weiss DS1 interface.

Lower Area

Bypass

A click-free and latency compensated smooth bypass of the plug-in. This is the same bypass as the button in the Extended Features panel.

Side Chain Link

Sets if the gain reduction of a stereo track should be linked (same gain reduction for both channels), or unlinked (individual gain reduction per channel.)

In the "cog wheel menu" it is possible to set the amount of linking, from 0% (unlinked) to 100% (fully linked).

As a rule of thumb, if you have drastic compression with lots of gain reduction, you want left and right channels to be linked and compress equally. This is to avoid the sound stage to move around when compression hits. With a more controlled gain reduction, you can reduce the side chain linking to maintain a wider stereo image. In mix situations, you typically want linked channels, while in mastering it is common to use unlinked channels.

Safety Limiter

A safety limiter to avoid audio levels above 0 dB.

In the "cog wheel menu" it is possible to change the threshold (ceiling) of the safety limiter.

Filter Types

Weiss DS5 has three different filter types: Static, Dynamic and Linear phase.

Depending on the usage, the modes have different benefits and drawbacks. Dynamic Phase has no latency and a phase shift similar to an analog equalizer. This mode can also be called minimum phase. In some cases, the quick attenuation of a band will be slightly more audible than in Linear Phase mode because of the rapid change in phase. But for most mix work, Dynamic Phase should be the go-to mode.

The Static and Linear Phase modes have a different topology where the change in gain (through gain reduction and make-up gain) does not alter the phase of the audio. Instead, the phase shift is solely determined by the cross-over frequencies and the amount of enabled bands. These modes will be very transparent for rapid changes in gain.

Static Phase has a constant phase shift, regardless of whether the compressors are working or not, and in Linear Phase this phase shift has been compensated and exchanged for a long latency (shift in time rather than phase). If you need low latency, Static Phase and Dynamic Phase are the best methods.

Static Phase

Has a static phase shift that does not depend on the level of gain reduction or make-up gain. No latency.

Dynamic Phase

The phase will change depending on the gain reduction or make-up gain. With a flat frequency response, there will be no phase shift at all. No latency.

Linear Phase

Same topology as Static Phase, but the phase shift has been compensated for, and the plug-in has an added latency instead.

This mode uses the same type of linear phase compensation technology as in the Weiss EQ1 hardware.

Macro Controls

The five knobs in the center will by default control all bands simultaneously, unless you select a band ("Only Selected Band"). It is possible to select multiple bands by Shift-clicking on a band in the upper area.

To further facilitate the usage, the macro knobs can also tilt the settings for the bands, either by pressing Tilt All Bands to the right of the knobs, or by holding Shift while adjusting the knob. This is useful to for example quickly setup faster attack times for the higher bands, or a higher threshold for the lower bands.

When using automation, the macro controls will write the parameters that they control. So to automate the Threshold, you need to set each band's Threshold in write mode.

Threshold

Sets the Threshold on all bands. From -60 to 0 dB.

Gain Reduction LEDs are positioned above the Threshold control. A yellow LED indicates that the band is compressing, while a red LED indicates that it is expanding.

Ratio

Sets the Ratio on all bands. The ratio goes from 1000:1 (limiting) to 1:1 (bypass), all the way up to 1:5 (expanding).

Attack

Sets the Attack on all bands. From 20 microseconds to 800 ms.

Release

Sets the Release Fast, Average and Release Slow parameters on all bands. From 20 microseconds to 8 seconds.

Make-Up Gain

Sets the Make-Up Gain on all bands. From -24 to 24 dB.

Hover the mouse pointer over a macro control to see the numerical read-out per band in the upper area. Hovering the Threshold, Ratio or Make-Up Gain will highlight its respective control in the upper area which makes it easy to see the current settings.

Macro Function

Sets how the macro controls behave:

• Single Band: Only the currently selected band will be affected by the knob changes. Select a band by clicking on it in the upper area.

• Tilt Bands: The settings will be changed in a see-saw fashion for all, or all selected, bands.

• All/Selected Bands: All, or the selected, bands will be affected by the macro controls.

• Weiss DS1: Opens the Weiss DS1 user interface for the currently selected band. This can also be achieved by double-clicking the band, or clicking the "Pen" icon at the top of the band.

Mix

Sets Dry/Wet for all bands. The dry path is not completely dry, since it handles the latency of the oversampling filters, and in Static Phase it also phase compensates for the phase shift.

The total gain in this knob depends on the setting of Parallel Mode in the cog-wheel menu. By default, it's set to X-Fade, which means that when you go from wet to dry, the wet path's gain will decrease while the dry path's gain increases, like a normal cross fader.

Keyboard Shortcuts

• Shift + drag: Tilts the settings of the different bands. Only applicable for the five macro controls.

• Command (Mac) or Control (Win) + drag: Fine adjust

• Option (Mac) or Alt (Win) + click: Return to default value

Upper Area

The upper area allows you to easily set the Cross-Over Frequencies, Threshold, Ratio and Make-Up Gain per band as well as get a clear overview with the different visualizations.

• Hover over a band to see parameter read-outs and the controls at the top.
• Click a band to select it. If a band is selected, the knobs at the bottom will only control that band. Otherwise, the knobs will control all bands simultaneously.
• Double-click on a band to open the Weiss DS1 user interface.
• Cmd + click (Mac), Ctrl + click (Win) to select multiple bands.
• Shift + click to select a range of adjacent bands that will be controlled simultaneously using the macro controls or the horizontal sliders.

Horizontal Lines

Each band has the following controls:

Make-Up Gain (red line)

The make-up gain sets the output gain for each band. -24 to +24 dB

Threshold (gray line)

Sets the threshold of the compressor.

Ratio (blue line)

Sets the ratio of the compressor. Values above the 0 dB line indicates that it is expanding rather than compressing.

These settings can also be adjusted using the macro controls. If only a single band is selected (by clicking that band), only that band will be affected by the macro controls.

At the top of each band are four controls which are visible when you hover your mouse over a band.

On/Off

Enables or bypasses the band

Solo

Solos the band

Open Weiss DS1 (pen icon)

Opens the Weiss DS1 user interface for that band

Double-click the band to quickly open the Weiss DS1. Click the background (upper area) to close it.

Vertical Lines

Each vertical line represents the cross-over frequency next to the band. Click and drag to change it.

X-Over Low, X-Over Low Mid, X-Over High Mid, X-Over High

Sets the cross-over frequency between the bands

Add/Remove Band (+ and - icons)

Removes or adds a band. From two to a max of five bands.

It is possible to disconnect the detector (side chain) bands from the compressor bands from the Weiss DS1 expert panel.

Visualizations

Gain Reduction Lines

The gain reduction is visualized using the solid lines. Different colors are used depending on the channel configuration:

Red: Stereo or Right
Gray: Left
Yellow: Mid
Green: Side

Gain Reduction Area

The transparent filled red or gray area also represents the gain reduction, but calculated differently. It estimates the difference between the input and output of the Weiss DS5 and displays that total difference.

This visualization depends on the input audio and can show the actual change, but is much slower than the gain reduction lines, and will not react to fast changes in audio. It is based on input and output frequency analyzer and will have limited resolution in the low frequencies.

The "Cog Wheel" Menu

The "Cog Wheel" menu contains global settings that will affect all bands, or all visualization.

Weiss DS1 Extra Parameters

Side Chain Link Amount

Sets how linked the left and right channels are when a band is set to "Stereo". At 100 % both channels will get the same gain reduction, while at 0 % the channels are unlinked and have separate gain reduction.

Typically, an unlinked side chain leads to a wider stereo image, but can cause problems with the stereo panorama for high gain reduction.

Preview

Sets the amount of preview (lookahead) for all bands. Whenever Preview is set at a value higher than the minimum value (0.02 ms), we will add 63 ms of latency to the algorithm.

RMS

Expert parameter. Sets the time constant with which the peak detection algorithm in the release circuit is calculated. Affects mainly Release Fast.

Safety Limiter Ceiling

Sets the threshold for the safety limiter.

Parallel Mode

Sets how the Mix knobs functions. The two modes are essentially the same, but are differs in how the output volume changes.

• X-fade blends the dry and wet signal, so at 50%, both are attenuated with 6 dB. If both signals have the same level, the output level will stay the same. This is the standard type of Dry/Wet control.

• Inject maintains the gain of the dry or wet signal until you reach the 50% point, where both signals are 0 dB. This is similar to how the original DS1-MK3 handled parallel compression.

Solo Mode

Switch between Solo and Audition modes.

• Solo will solo the current band by muting the other bands. This mode is useful to set cross-over frequencies.

• Audition will output the difference, the delta, between input and output on the current band. That means that if there is no compression, the output will be silent. This mode is useful if you need to audition the actual gain change for a band.

Low Latency

Forces Filter Mode and Preview to settings that have low latency. In the Filter Mode case, it will set it to Static if it's previously in Linear Phase mode. Preview will be set to its minimum position (20 μs). Some DAWs require the transport to be stopped and restarted for the latency change to take place.

Latency

There are two main components in the Weiss DS5 that will add latency, the Linear Phase filter and the Preview ("lookahead") function of the compressor. In Low Latency mode, both of these will be switched off.

The latency in Low Latency mode, or when using Static or Dynamic Phase filters without compressor Preview is the following.

44.1 kHz	48	88.2	96	176.4	192 kHz
4.5 ms	3.3 ms	2.4 ms	2.3 ms	1.3 ms	1.3 ms

Preview adds an additional 72 ms, and Linear Phase adds an additional 372 ms.

Visualization Parameters

Block Size

Sets the block size of the frequency analyzer. Smaller block size leads to faster response times, but worse frequency resolution

Mode

Sets the response time of the frequency analyzer (Fast/Slow)

Graph Range

Sets the zoom of the Gain Reduction Lines (+/-3, 6, 12, or 18 dB)

Analyzer Tilt

Sets the tilt of the frequency analyzer (Flat, 3, 4.5 or 6 dB tilt)

Smoothing

Sets the frequency smoothing of the frequency analyzer (Off, 1/6th octave, 1 octave)

Weiss DS1

Double-clicking on a band, or clicking the "pen" icon at the top of the band, will open up the "expert panel" of the Weiss DS1. The Weiss DS1 is the line-by-line port of the original Weiss DS1-MK3, although some features have been added (cross-over frequencies), while others been removed (channel controls, band-pass filter, limiter) to accommodate the design of the DS5.

On

Turns the current band on/off. Also found as an icon at the top of each band.

Solo

Solos the current band. Also found as an icon at the top of each band.

Apply Current Settings To All Bands

Copies the DS1 settings of the current band to all other bands. Only the ten compressor parameters will get copied (Attack, Release Delay, Release Fast, Average, Release Slow, Soft Knee, Threshold, Ratio, Range and Make-Up), not the cross-over frequencies or any buttons.

Channel Mode

Sets the channel mode for the current band

• Stereo: Weiss DS1 operates in stereo.

• Left or Right: Only the left or right channel will be affected by the Weiss DS1.

• Mid or Side: Only the mid (L+R) or the side (difference, L-R) will be affected by the DS1.

Detector Side Chain

Side Chain

Sets internal or external side chain

• Int: Uses the internal side chain

• Ext: Uses the external side chain

SC/Comp Filters

Sets whether the detector filters should be the same as the compressor filters (Band), or if the detector filters are separate from the compressor filters (Free)

• Band: Normal mode, the compressor will listen for audio in the same band as it will compress the signal.

• Free: Expert mode. The compressor listens for audio in a separate frequency range, but compresses the audio within the band.

Free is useful if you need to carve out space for vocals in a dense instrumental, or if you want to expand the high frequencies every time a kick drum hits.

In Free mode, two yellow "flags" will appear in the main window, and these determine the frequency band of the detector filters.

Upper

Sets the upper frequency range of the band in Band mode, or the upper frequency range of the detector in Free mode.

Lower

Sets the lower frequency range of the band in Band mode, or the lower frequency range of the detector in Free mode.

Compressor Controls

For a more detailed explanation of the Weiss DS1 controls, please see either the manual for the Weiss DS1-MK3 plug-in, or the manual for the original Weiss DS1-MK3 hardware.

Timing Controls

Attack

Sets the attack time of the compressor. (Also controlled by the macro controls.)

Release Delay

Sets a delay time before the release phase begins. The resulting dynamic characteristic is very smooth and avoids otherwise typical "pumping" effects. The ideal setting is program dependent and experimentation may be necessary to achieve the best combination of all dynamic parameters.

The audio is monitored by two different methods, peak amplitude and RMS, and by comparing these two methods it determines whether it should apply a short (Release Fast) or a long (Release Slow) release. A short transient will trigger the fast release. The Average knob controls the transition between the fast and slow release times.

With a fast Average setting, most of the gain reduction depend on the Release Fast setting. With a slower setting, only the first part of the release will depend on Release Fast while the rest is handled by Release Slow

Release Fast

Sets the fastest release time, which will be used for transient peaks. (Also controlled by the macro controls.)

Average

Sets how long time it will take to go from the fast release time to the slow release time. With a longer Average, you need longer sustained peak level for the compressor to start using the Release Slow time. (Also controlled by the macro controls.)

Release Slow

Sets the slow release time, which will be used for consistently loud audio. (Also controlled by the macro controls.)

There is an expert parameter, RMS, in the cog-wheel menu that can be used to change the calculation of the peak amplitude detection mentioned above.

Compressor Curve Controls

Soft Knee

Sets the hardness of the knee, from 0% (hard) to 100% (soft).

Threshold

Sets the threshold of the compressor, from -60 dB to 0 dB. (Also controlled by the macro controls.)

Ratio

Sets the ratio of the compressor. Settings from 12 o'clock to max are downwards compressing, from 1:1 to 1000:1, while settings between min and 12 o'clock are upwards expanding, from 1:5 to 1:1. (Also controlled by the macro controls.)

Range

Sets the maximum allowed gain reduction, from Full range (no limit) to 0 dB (no compression allowed).

Gain

Make-Up Gain

Sets the output level of the compressor. (Also controlled by the macro controls.)

Display

The display shows the input peak level (-24 to 0 dB), the gain reduction (0 to -12 dB), the shape of the compressor knee (-60 to 0 dB) as well as the output peak level (-24 to 0 dB).

In upwards expansion mode, the gain reduction meter will turn red to indicate that it is adding gain instead of removing it.

Please note that for Left, Right, Mid, and Side modes, only one channel of the stereo meters are used.

Safety Limiter

Weiss DS5 Multiband Compressor can get loud, especially when using the expanding ratios. To prevent accidental over s and protect your ears and equipment we added a safety limiter at the very output of the plug-in, after the Mix knob.

The limiter is a low latency true peak limiter that will limit the audio to the level set by the Safety Limiter Ceiling control in the cog-wheel menu, with a default value at 0 dB (true peak).

The Safety Limiter uses oversampling in its side chain to detect true peaks and applies the calculated gain reduction to the non-oversampled signal. The side chain uses 4x oversampling at 44.1/48 kHz and 2x at 88.2/96/176.4/192 kHz. While this approach accurately detects and suppresses true peaks, high amounts of gain reduction can cause the limiter itself to generate new true peaks over the ceiling. Most true peak limiters address this with a second gain reduction smoothing stage at the cost of increased latency and processing power. To keep both to a minimum, this stage was omitted.

Presets by Bob Katz

In the words of Bob Katz:

"I've designed a few presets with different philosophies, to take advantage of the versatility of the DS5. One of them I call "tonalization," ("Presence and Spacious Parallel Comp" and "Warm and Spacious Parallel Comp.") which mixes in extreme compression in parallel with the "dry" signal. You can warm up the ambience of the signal or conversely add presence in one or more bands while retaining transients, very helpful in mastering.

Tonalization can be either quite subtle or strong in character, just by changing the wet/dry ratio. Probably, you won't have to fiddle with thresholds, ratios or time constants if you're looking to "fill in the holes" or give a sense of "spacious ambience". The only controls you might want to change are makeup gains and possibly wet/dry ratio.

The next preset is Subtle Downwards Master Comp., which can be extremely invisible, adding a light touch in mastering to help glue the sound of a slightly ragged mix. This preset is so easy to set up it's hardly necessary, but nice to have as a start-off point when you desire subtle, invisible compression. The first and perhaps the only control you may need to change is Threshold, adjust all the thresholds together up or down to get the amount of action you are looking for.

Another preset I made was Hard Rock Master, to demonstrate that the DS5 can be used to help the punch of aggressive music (e.g. hard rock). Since every piece of music is so different, you can use this as a starting point or an example and then, like all presets, do final tweaks yourself.

One preset I did not create yet is one with upward expansion, which can be very helpful to enhance a snare drum, for example. Or the liveliness, clarity, and punch of a slightly squished mix. I'll work on creating that in the near future.

Like all good presets, these are examples, starting points. I tried to make the presets so that with a lot of different music you only have to concentrate on one or two controls for the music you are working with."

Architecture

This is a simplified block diagram for 44100 and 48000 Hz sample rates. For higher sample rates, omit the up- and down-samping blocks.

Keyboard Shortcuts

When using a macro knob:

• Shift + drag: Tilts the settings of the different bands

When using any knob:

• Command (Mac) or Control (Win) + drag: Fine adjust

• Option (Mac) or Alt (Win) + click: Return to default value

Selecting bands:

• Click a band to select it. If a band is selected, the macro controls at the bottom will only control that band. Otherwise, the knobs will control all bands simultaneously.

• Double-click on a band to open the Weiss DS1 user interface.

• Command (Mac) or Control (Win) click to select multiple bands.

• Shift + click to select a range of adjacent bands that will be controlled simultaneously using the macro controls or the horizontal sliders.

Credits

Thomas Andersson - Signal processing
Cameron Clark - Signal processing, UI programming, presets
Niklas Odelholm - Filter design and product design
Patrik Holmström - Framework programming, UI programming
Arvid Rosén - Weiss DS1-MK3 signal processing
Johan Bremin - Quality assurance, testing, and presets
Todd Urban - Presets
Stefan Aronsson - Presets

...with special thanks to

Joschka and Daniel Weiss - Original product design, presets and quality assurance
Bob Katz - Original DS1-MK3 presets, presets, beta testing
Philippe Weiss (W3ISS) - Presets, beta testing
Maor Applebaum Mastering - Presets
Jonathan Wyner - Presets
Thomas "Plec" Johansson - Presets
Md3sign Studios - Presets