Building complex reverbs using ValhallaÜberMod

The original ValhallaÜberMod concept had a fairly sparse Diffusion section, which was intended to smooth out feedback echos and add some density to chorus patches. Somewhere during the development process, the diffusion block was expanded into a much more powerful DIFF section, with each input channel being processed by a dense modulated diffusion block with variable size. The DIFF section proved useful in creating dense nonlinear reverbs, as well as lush ambient reverbs and decent plate simulations. The ÜberMod controls aren’t designed around creating reverbs, so I figured that any reverbs created with ÜberMod were a cool bonus with that plugin.

Flash forward to a few days ago, where I found myself experimenting with ÜberMod, mainly as a way of procrastinating before I get back to work on my next plugin. I started running multiple instances of ValhallaÜberMod in series and parallel, and using the sends of my DAW to control the routing and levels. To my surprise, I found that I was able to create some VERY complex and subtle reverbs using ÜberMod, by allocating different instances of the plugin for different stages of the reverb decay.

EXAMPLE 1: Medium Vocal Reverb, w/early reflections

The first example uses 3 instances of ÜberMod, running on 2 different sends. The first instance is running on its own send, and will cover the early reflections stage of a reverb:

<ValhallaUberMod pluginVersion="1.0.1" presetName="RandomizedEarlyReflections" Mix="1" Depth="1" StereoWidth="0.5" Delay="0.0476999991" Feedback="0" Spread="1" Slope="0.643999994" Skew="0.175999999" Random="1" TapGain="0.5" Diffusion="0.624000013" DiffSize="0.0163265299" DiffModRate="0.0490490496" DiffModDepth="0.5" LowCut="0.0351758786" HighCut="0.232160807" SpatialXover="0.145728648" DetuneRate="0.00900900923" DetuneDepth="0.851999998" VibratoRate="0.298245579" VibratoDepth="0" OverMod="0.0313131325" DriveInGain="0.375" DriveOutGain="0.75" DriveNoiseGain="0.333333343" FeedbackRotate="0.5" SmoothingTime="0.0990990996" ColorMode="1" DelaySync="0" type="0.333333343" DiffEnable="1" Drive="0" DrivePrePost="1" Speed="0" InputPan="0.125"/>

This preset uses the 16Tap mode, in conjunction with the DIFF section, to create a dense early ambience that abruptly cuts off after about 50 to 100 millseconds. The TAP Slope parameter is used to create the perception of a room with a short to medium decay, and the DELAY slider determines the point at which this decay is truncated. Some slow LFO modulation is used in conjunction with the MOD OverMod control to randomize the reflections.

The second instance of ÜberMod is running on a separate send, and provides the input diffusion of the late reverb tail:

<ValhallaUberMod pluginVersion="1.0.1" presetName="InputDiffusion" Mix="1" Depth="0.444000006" StereoWidth="0.5" Delay="0.00999999978" Feedback="0" Spread="0.5" Slope="0.5" Skew="0.5" Random="0" TapGain="0.5" Diffusion="0.703999996" DiffSize="0.0653061196" DiffModRate="0.0130130127" DiffModDepth="0.395999998" LowCut="0" HighCut="0.387939692" SpatialXover="0.145728648" DetuneRate="0.0370370373" DetuneDepth="0.5" VibratoRate="0.298245579" VibratoDepth="0" OverMod="0" DriveInGain="0.375" DriveOutGain="0.75" DriveNoiseGain="0.333333343" FeedbackRotate="1" SmoothingTime="0.0990990996" ColorMode="0" DelaySync="0" type="0.0416666679" DiffEnable="1" Drive="0" DrivePrePost="1" Speed="0" InputPan="0.125"/>

This preset uses the 2TapChorus mode, but most of the work is being done by the DIFF section. A fairly short DIFF size is used, with the idea being to turn impulsive sounds into a “puff” of diffuse energy. This will smooth out any reverb that this preset is placed in front of.

The third instance of ÜberMod is placed in series after the second instance (i.e. on the same send), and generates a reverb tail with a medium decay:

<ValhallaUberMod pluginVersion="1.0.1" presetName="MediumLateReverb" Mix="1" Depth="0.5" StereoWidth="0.5" Delay="0.00999999978" Feedback="0.612999976" Spread="0.5" Slope="0.5" Skew="0.5" Random="0" TapGain="0.5" Diffusion="0.748000026" DiffSize="0.240816325" DiffModRate="0.0290290285" DiffModDepth="0.5" LowCut="0.0954773873" HighCut="0.288442224" SpatialXover="0.145728648" DetuneRate="0.0490490496" DetuneDepth="0.5" VibratoRate="0.298245579" VibratoDepth="0" OverMod="0" DriveInGain="0.375" DriveOutGain="0.75" DriveNoiseGain="0.333333343" FeedbackRotate="1" SmoothingTime="0.0990990996" ColorMode="0" DelaySync="0" type="0.0416666679" DiffEnable="1" Drive="0" DrivePrePost="1" Speed="0" InputPan="0.125"/>

The above late reverb preset also uses the 2TapChorus mode, with most of the work being done by the DIFF section and the FEEDBACK control. The Diffusion is set to a fairly large size. The DIFF Size, in conjunction with the feedback and filtering, determines the length of the reverb decay. The WARP fBMix control is set to 100%, to create a figure-8 (ping-pong) feedback loop, as used in reverbs by Lexicon & Alesis.

Once you have the basic routing set up, experiment with the send levels being sent to the Early Reflections (instance 1) and the Late Reverb (instances 2 and 3). I have found that it sounds best with the Early Reflections set to a somewhat higher level than the Late Reverb.

EXAMPLE 2: Randomized Hall

ValhallaÜberMod is versatile enough that you can emulate many types of reverb structures, not just the Early Reflection / Late Reverb division of the more “scientific” reverbs. For example, Lexicon’s Random Hall is known for its high echo density, and the soft attack derived from the Shape and Spread controls. To emulate this soft attack using ÜberMod, we’ll use 2 instances of ÜberMod in series. The first is used to approximate the Shape/Spread section of Random Hall:

<ValhallaUberMod pluginVersion="1.0.1" presetName="ShapeSpread" Mix="1" Depth="0.444000006" StereoWidth="0.5" Delay="0.342900008" Feedback="0" Spread="1" Slope="0" Skew="1" Random="1" TapGain="0.5" Diffusion="0.791999996" DiffSize="0.134693876" DiffModRate="0.0130130127" DiffModDepth="0.395999998" LowCut="0" HighCut="0.975879371" SpatialXover="0.145728648" DetuneRate="0.0370370373" DetuneDepth="0.5" VibratoRate="0.298245579" VibratoDepth="0" OverMod="0" DriveInGain="0.375" DriveOutGain="0.75" DriveNoiseGain="0.333333343" FeedbackRotate="1" SmoothingTime="0.0990990996" ColorMode="0" DelaySync="0" type="0.375" DiffEnable="1" Drive="0" DrivePrePost="1" Speed="0" InputPan="0.125"/>

This preset uses the 32Tap mode, with a fair amount of Diffusion, and the TAP Slope set to -100%, to create a nonlinear reverb that fades in gradually over time.  The attack time is determined by the DELAY slider.
The ShapeSpread preset is used in series with a 2nd instance of ÜberMod on the same send, that adds a huge reverb tail to the slow attack:

<ValhallaUberMod pluginVersion="1.0.1" presetName="BigLateReverb" Mix="1" Depth="0.760999978" StereoWidth="0.5" Delay="0.00999999978" Feedback="0.768000007" Spread="0.5" Slope="0.5" Skew="0.5" Random="0" TapGain="0.5" Diffusion="0.843999982" DiffSize="0.448979586" DiffModRate="0.0730730742" DiffModDepth="0.495999992" LowCut="0.0502512567" HighCut="0.340703517" SpatialXover="0.145728648" DetuneRate="0.033033032" DetuneDepth="0.5" VibratoRate="0.298245579" VibratoDepth="0" OverMod="0" DriveInGain="0.375" DriveOutGain="0.75" DriveNoiseGain="0.333333343" FeedbackRotate="1" SmoothingTime="0.0990990996" ColorMode="0" DelaySync="0" type="0.0416666679" DiffEnable="1" Drive="0" DrivePrePost="1" Speed="1" InputPan="0.125"/>

This preset is very similar to the earlier late reverb preset, but with a much greater DIFF size setting. In addition, the WARP Speed is set to 1/2, which doubles the size of the diffusors, to create a HUGE reverb decay.

ROLL YOUR OWN SOUNDS

The above examples are just 2 quick demos of the complex reverb responses that can be generated with multiple instances of ValhallaÜberMod. For example, a longer gated reverb could be used in parallel with a reverb that incorporates DRIVE in the feedback loop, to create a reverb that starts off clean, then turns nasty after a certain amount of time.

ÜberMod is also useful in extending the capabilities of other reverb plugins. For example, the InputDiffusion or ShapeSpread examples from above can be used in series with ValhallaRoom, to create a super lush reverb that has more “standardized” reverb controls. The RandomizedEarlyReflections example can be added in parallel to ValhallaShimmer, to add early reflections to the modulated Shimmer late decay. Or combine ÜberMod with any other reverb plugin, algorithmic or convolution, as you see fit.  The low CPU consumption of ÜberMod makes it easy to use it in conjunction with other plugins.

It is worth noting that the same process can be used in the construction of all sorts of complicated sonic events, not just reverbs. ValhallaÜberMod excels at choruses, ensembles, multitap delays, echos, and so forth. By combining different settings of ÜberMod in series and parallel, all sorts of weird and wonderful sounds can emerge. I encourage people to use ÜberMod as a modular building block for creating all sorts of complex effects.

ValhallaUberMod: The Preset Menu

ValhallaÜberMod has a cross-platform preset format, allowing users to use the same presets for all plugin types (RTAS/VST/AU, for both OSX and Windows). The preset format is based around XML, which allows presets to be copied and pasted into emails, forums, or any other place that can accept text.

To access the presets, simply click the name of the active preset, to the right of the PRESET: text in the lower right side of the GUI (the plugin will display “Default” when first opened):

The Preset Menu will display when the current preset name is clicked:

To select a preset, simply mouse over the given preset name, and release the mouse button. Mouse over a given preset folder name (the ones with the triangle to the right) to view and select presets within that folder.

To save a preset, simply select “Save as…” from the menu. This will allow you to name your preset, and choose the folder to save the preset to, or to create a new folder for your preset.

If you wish to copy a preset from a forum or blog post, simply select the text with your mouse (including the < and > closing tags), and copy the text (Command+C on OSX, CTRL+C on Windows). Then, select the “Paste from Clipboard” option from the preset menu.

If you want to share a preset with someone, select the “Copy To Clipboard” option, then simply paste the text (Command+V on OSX, CTRL+V on Windows) into the document/email/forum where you want the preset to be.

Special thanks to Randy Jones of Madrona Labs for developing the original text-based preset code that I ported over to ValhallaRoom and ValhallaÜberMod.

ValhallaUberMod: The High Level Controls

ValhallaÜberMod has a minimalist GUI that is closely related to the previous Valhalla DSP plugin, ValhallaRoom. The basic concept is that the GUI reflects the hierarchy of the underlying algorithms:

• The larger vertical sliders are used for the high level parameters. These are the controls that have the widest, most immediate impact on the sound of the effect.
• The smaller knobs are contained within a window, with the particular knobs to be viewed selected by various “buttons” (rounded rectangles, to be precise) above the window. This is similar to the tabs concept in web browsers. Each button or tab selects a group of related controls, which tend to control the “tweakier” low level parameters.
• The GUI has been organized around the idea that the user will dial in a specific sound via a combination of high level sliders and lower level knobs, with the high level sliders being used for broad overall changes to the sound, and the lower level knobs for fine tuning the sound.

High level controls, and the buttons used to select what knobs are visible in the “tweak” window, are represented in upper case. For example, DEPTH will be used to refer to the high level slider, while MOD refers to the button that selects the knobs used for fine tuning the modulation parameters.

A combination of upper and lower case words refers to a specific low level parameter. So, “MOD SlowDepth” refers to the knob under the MOD tab (inside the MOD window, selected by the MOD button,  part of the MOD menu, however you want to think about it) that adjusts the depth of the slow modulation waveform.

There are 5 high level sliders in ValhallaUberMod, and 2 combo boxes associated with these controls:

The sliders:

• MIX: Controls the ratio of the dry input to the “wet” (delayed/chorused) output, displayed as a percentage. 0% corresponds to an entirely “dry” output (i.e. no effect), while 100% corresponds to an entirely “wet” output where only the delayed signals are present. In general, you will want to use a MIX setting of 100% for sends, and play around with the MIX level when ÜberMod is used as an insert.
  • MIX LOCK: The label of the MIX slider (i.e. the word “MIX” above the slider) does double duty as a mix lock. Click on the label, and the MIX slider will be grayed out. This is useful for maintaining a fixed mix level when browsing through presets.
• DEPTH: Controls the overall modulation depth of the algorithm, displayed as a percentage. This acts as a scale on the various slow and fast modulation depths that are adjusted by the MOD controls.
• WIDTH: Controls the overall width of the spatial image of the “wet” (delayed) signal, as a percentage.
  • A WIDTH setting of 0% sums the left and right delay output signals, such that the same delay mix is present in left and right channels.
  • A WIDTH setting of 100% is fully stereo: the outputs of the left delay line are sent to the left output only, and the right delay line to the right output only.
  • At settings above 100%, the high frequencies from one channel are inverted and added to the opposite channel, to create a “super-stereo” spatial image that can sound like it is coming from outside the speakers. The crossover for the high frequencies is set by the EQ SpatialEQ control.
• DELAY: Controls the delay of the longest output taps, in milliseconds. The delays of the individual taps will be dependent on the settings in the TAPS menu, but the longest tap will have a base delay that corresponds to the DELAY setting.
  • It is worth noting that there are various low level controls that have an effect on the actual delay time of ÜberMod, in addition to the DELAY slider. For example, the WARP Speed control, when set to 1/2X, results in a delay that is double the DELAY setting, while halving the output bandwidth. In addition, high amounts of modulation width can cause the delay to deviate considerably from the value displayed by DELAY, and the DIFF section adds its own delay. These will be discussed in future blog posts.
• FEEDBACK: Controls the amount of feedback around the network, as a percentage. The feedback path in ValhallaUberMod has been set up to be stable with feedback gains up to 100%, assuming that DRIVE isn’t enabled.

The combo boxes:

• MODE: Selects the particular delay/chorus mode to be used. Each mode is a separate algorithm, that makes use of a specific number of output taps (reflected in the algorithm name) and a specific modulation scheme. The different modes will be explored in the next few blog posts.
• SYNC: Selects the delay sync ratio of the longest taps. “Free” means that the delay time is specified by the DELAY slider, while the other values are specified in rhythmic groupings that are derived from the DAW tempo. A “.” indicates a dotted note of that time division, i.e. 1/8. is a dotted eighth, or 3/16ths. A “T” indicates a triplet division.

ValhallaRoom V1.0.6: Introducing Dark Room

I have just released version 1.0.6 of ValhallaRoom. You can download the demos from the usual place, and all current ValhallaRoom customers should have received a link to the updates (send me an email if you haven’t received your links yet).

In addition to a few bug fixes, version 1.0.6 introduces a new reverb mode to ValhallaRoom: Dark Room. This new reverb departs from the high fidelity path taken by the other 4 reverb modes in ValhallaRoom. It is deliberately low-fi, with noisy interpolation, no high frequencies above 11 kHz, and a late reverb that can have a low initial echo density. It also has a wide stereo image, a clear decay with lush randomized chorusing, and sits in a mix quite nicely. An added bonus is that the CPU is significantly lower than the other ValhallaRoom reverb modes.

Why add a lo-fi reverb mode to ValhallaRoom? I’m not really sure. After doing this for about 12 years, I’ve learned to follow my instincts on this stuff, even if it takes me in strange directions. Plus, I wanted to add something new to ValhallaRoom, as a way of saying thanks to all of the customers who have supported my work.

I was also inspired by some recent studies of the Lexicon 224, the EMT250, and other vintage reverbs. These early digital machines often had very noisy interpolation, sparse initial echo density (at least by modern standards), and sampling rates that seem primitive today. They also were useful for creating a “larger-than-life” sound, that is described to this day as warm and spacious. I noticed that a lot of these classic reverbs had a very limited frequency response, so I figured it would be worth adapting some of these old-school limitations to the more modern algorithm architectures found in ValhallaRoom.

Dark Room has identical controls to the other reverb modes, but produces a noticeably different initial sound. With Early Send set to 0, the Late Decay can have a marked amount of initial “flutter” or “grain,” similar to the 224 Concert Hall with the Diffusion control set low. A few usage tips:

• The Late Size control can be used to adjust the speed of the “flutter,” with larger sizes corresponding to more obvious and slower echos.
• By setting Early Send to 1.0, and adjusting the Early Size to 40 msec or later (depending on the Late Size), the flutter in the Late reverb can be totally eliminated. This is similar to how the Diffusion control works in older Lexicons, but with the advantage that the Early reverb has far less coloration than the series allpasses used for the diffusors in many “classic” reverbs. The Late Size can then be adjusted to get the desired stereo width – this can get really big.
• Setting DEPTH to 1.0 results in the most “vintage” sound, while values less than 1.0 allow the user to dial in some early reflections.
• With Early Send set to 1.0, and using larger Early Size values (>100 msec), the Late Reverb will have a slower initial attack. This is similar to how the Depth control worked on the 224 and 224X/L, as well as the Shape and Spread controls on the 480L and later reverbs.
• The Late High Mult and Late High Xover have an effect on the initial tone of the late decay, similar to the Concert Hall algorithm on the 224XL and the Small/Large Concert Hall B on the 224. By setting High Mult to 0.1X, the user can simulate the -6dB/octave filters used on these older boxes.
• Turn up the Early and Late Mod Depth when using Dark Room. The older algorithms used a LOT of pitch modulation to avoid metallic decays. The Dark Room algorithm uses a different architecture that is less prone to sounding metallic, but if you want that big, lush, spacey decay, modulation is a must.

Here’s a preset that can be used as a good starting point for the Dark Room reverb mode:

<ValhallaRoom pluginVersion="1.0.6" presetName="DarkStartingPoint" mix="0.289999992" predelay="0" decay="0.0265265256" HighCut="0.58523488" earlyLateMix="1" lateSize="0.720000029" lateCross="0.25999999" lateModRate="0.202020198" lateModDepth="0.430000007" RTBassMultiply="0.413333327" RTXover="0.0666666701" RTHighMultiply="0" RTHighXover="0.410067111" earlySize="0.0581581593" earlyCross="0" earlyModRate="0.0909090936" earlyModDepth="0.800000012" earlySend="1" diffusion="1" type="0.416666657"/>

ValhallaRoom Tips and Tricks: Cathedrals

The 1.0.4 version of ValhallaRoom added a set of Cathedral presets, that were dialed in from published acoustic measurements of various Italian cathedrals. A few hints in dialing in a cathedral sound:

• Turn DECAY up to correspond to the midrange decay rate. Gothic cathedrals can have decays up to 12 seconds long, while cathedrals from other eras tend to be smaller and have shorter decay times.
• Late Size should be set to a high setting, to reflect the high modal density of these spaces.
• The Early Size control should be used to generate a bit of a “fade-in” for the decay. Due to the large size of cathedrals, it takes a fair amount of time for the energy to build up in the space, which translates to a slow attack for the decay time. A good rule of thumb is to use an Early Size setting of 1/20th of the decay time (up to 500 msec or so for truly large cathedrals).
• In order to get the “fade-in” effect from Early Size, set Early Send to 1.0, and DEPTH to 100%.
• The Late High Mult should be set to a low value, such as 0.1x. The sheer volume of air contained in a cathedral adds a huge amount of high energy loss.
• Set the HIGH CUT and Late High Xover to get the required amount of brightness in the sound. Lower frequencies would be more realistic, but higher frequencies might be better for that “heavenly” sound.
• For a realistic sound, leave the Early Mod Depth low, but don’t be afraid to turn up the Late Mod Depth. In order to properly capture the modal density of a cathedral, a digital reverberator would have to use several minutes of delay memory, which would put the CPU and memory consumption well outside of the real-time range for any modern computer. Modulated delays are a good way of creating the impression of higher modal densities. Plus, they sound purty.

 

ValhallaRoom Tips and Tricks: Unnatural Hall Reverbs

In one of my previous posts, I described the characteristics of “real-world” concert halls, and how to emulate them with ValhallaRoom. In general, real concert halls have a fairly fast onset of reverberation, a decay time between 1.6 and 2.1 seconds, and a somewhat longer decay time at low frequencies than at mid-frequencies. A realistic emulation would use subtle amounts of modulation, in order to create the perception of a high modal density without pitch change.

This is all fine and dandy for real concert halls, but what about unrealistic concert halls? The earliest commercial reverbs, the EMT250 and the Lexicon 224, were both created in order to emulate concert halls. With the limited amount of memory available for delay lines, both of these reverbs turned to large amounts of time variation in order to avoid metallic decays. The sonic results were big, washy, chorused decays that could stretch to 70 seconds and beyond. No “real” concert hall sounds like this – but it is a great sound. In addition, hardware units like the 224, 224XL and 480L had the ability to artificially elongate the attack portion of the reverb, such that the reverb sound would “fade in” to a much greater degree than a real hall. Not realistic, but useful for creating a bit of separation between an input signal and the reverb.

Fortunately, ValhallaRoom excels at unnatural halls, in addition to emulating the “real thing.” A few tips for dialing in an unnatural, vintage digital hall sound:

• Set DECAY to whatever feels right. Many of the “Concert Hall” presets of classic digital reverbs have decay times of 6 seconds and up.
• Use the LATE Bass Mult to dial in the required clarity of the decay. Setting this <1.0X will result in a reverb that gets more trebly as it decays, which can be a nice sound.
• Turn up the modulation depth! Both Early Mod Depth and Late Mod Depth can be cranked up for that seasick decay. For less obvious detunings, use lower Mod Depth settings, but higher Mod Rates.
• The Bright Hall reverb mode can get much deeper and random modulations than the other modes.
• Set Early Send to 100%, Early Size to >100 msec, and DEPTH to 100%. The Depth control in early Lexicon reverbs, and the Shape/Spread controls in later Lexicons, allowed the user to dial in a slow attack on the reverb. By running the Early reverb into the Late reverb and using a large Early Size setting, you can create a reverb that fades in at the rate determined by the Early Size.
• The Early Diffusion control can be set to lower values, to emulate the grainy sound that many of the early reverbs had during the initial attack phase.
• Set HIGH CUT to somewhere between 5000 and 8000 Hz to simulate the dark sound of early, low-sampling rate reverbs.

The following preset implements a big digital hall sound:

<ValhallaRoom pluginVersion="1.0.5" presetName="BigDigitalHall" mix="0.425000012" predelay="0.0240000002" decay="0.0730730742" HighCut="0.44697988" earlyLateMix="1" lateSize="0.730000019" lateCross="0.709999979" lateModRate="0.155555561" lateModDepth="0.460000008" RTBassMultiply="0.166666672" RTXover="0.0787878782" RTHighMultiply="0.377777785" RTHighXover="0.474496633" earlySize="0.255655646" earlyCross="0.0299999993" earlyModRate="0.143434346" earlyModDepth="0.370000005" earlySend="1" diffusion="1" type="0.25"/>

Den (from the Gearslutz forum) posted this preset, reminiscent of the sounds of the Lexicon 224 Concert Hall algorithm:

<ValhallaRoom pluginVersion="1.0.1" presetName="BladeRunner" mix="1" predelay="0" decay="0.150750756" HighCut="0.294630885" earlyLateMix="1" lateSize="0.949999988" lateCross="0.150000006" lateModRate="0.191919193" lateModDepth="0.200000003" RTBassMultiply="0.666666687" RTXover="0.0494949482" RTHighMultiply="0.25555557" RTHighXover="0.289261758" earlySize="0.235135138" earlyCross="0.0199999996" earlyModRate="0.169696972" earlyModDepth="0.129999995" earlySend="1" diffusion="1" type="0.25"/>

A quick example of piano played through the above setting (piano played by Den):

Here’s a really big “concert hall” setting:

<ValhallaRoom pluginVersion="1.0.5" presetName="VideoIntro" mix="0.507000029" predelay="0" decay="0.300000012" HighCut="0.344966441" earlyLateMix="1" lateSize="0.579999983" lateCross="0.150000006" lateModRate="0.088888891" lateModDepth="0.280000001" RTBassMultiply="0" RTXover="0.113131315" RTHighMultiply="0" RTHighXover="0.2966443" earlySize="0.0440440439" earlyCross="0.0199999996" earlyModRate="0.169696972" earlyModDepth="0.129999995" earlySend="0" diffusion="1" type="0.25"/>

A simple electric guitar phrase (which was used on Gearslutz to test many reverb algorithms) through ValhallaRoom with the above settings:

UPDATE 1/2012: I just reread this blog post from last year (thanks to a link-back from an interesting blog post at The DIY Recordist). It is worth noting that ValhallaRoom has several new reverb modes that are well suited for emulating vintage digital halls. DarkRoom, Nostromo and Narcissus are reverb modes that are designed to have the “dark” coloration of the older reverbs, as well as a more gradual onset of echo density, noisier interpolation (to emulate the reduced bit width coefficients of the older boxes), and heavy randomized modulation.

ValhallaRoom Tips and Tricks: Realistic Concert Halls

ValhallaRoom was named for its ability to get realistic room sounds. From this perspective, a concert hall is nothing more than a really big room. The physics and reverberant characteristics of concert halls have been studied extensively in the last century, starting with the work of Wallace Sabine (the acoustic consultant for the design of Boston Symphony Hall) and continuing with the work of Leo Beranek, Yoichi Ando, Manfred Schroeder, and many other acoustic researchers.

Concert halls that are highly ranked by classical music listeners tend to have the following characteristics:

• A mid-frequency decay time of 1.6 to 1.8 seconds for music from the “Classical” period (1750 to 1820), and around 1.9 to 2.1 seconds for music from the “Romantic” period.
• An initial time-delay gap at or below 25 msec. This is the time between the direct sound and the first reflection, and produces a sense of “intimacy” for shorter settings. This is why the “shoebox” shaped halls tend to be preferred by conductors and audiences – the initial lateral reflections start rather quickly, due to the relatively short distance that sound has to travel from the orchestra to the side walls to the listeners.
• “Warmth,” in that the bass tones are strong. This translates to a low-frequency decay time that is somewhat longer than the mid-frequency decay time.
• Spaciousness, in that the sound seems to come from a space wider than the instrument making the sound. This tends to be tied into phase differences in the signals hitting the left and right ears (which is often referred to as the IACC, interaural cross-correlation).
• Envelopment, in that the reverberation appears to come from all directions, rather than from limited directions. In practice, this means that an ideal hall will mix the reflections together rather quickly, and won’t have any strong discrete echos from any one location, or a part of the hall where the reverb hangs around too long (as can happen in cathedrals with high naves).

Starting with the above criteria, we can dial in a realistic concert hall preset in ValhallaRoom. A few general principles:

• Set DECAY to 1.6 to 2.1, depending on the type of music that will be played in the space.
• Set HIGH CUT to a fairly low frequency, between 4500 Hz and 7000 Hz, to simulate the air absorption in the space.
• PREDELAY should be set to match the initial time delay gap of the hall being modeled, with 25 to 35 milliseconds being a more “realistic” setting, and shorter settings useful in generating intimacy.
• The Early Size parameter should be between 20 and 50 msec, with Early Send turned up full and Early Diffusion at max, in order to product a diffuse onset of reverberation.
• The Late Size should be set greater than 0.5. The largest settings of Late Size may produce audible reflections, depending on the mode used, so tune this by ear.
• The Late High Xover should be set low enough to cause a bit of rolloff in the decay (around 2 to 4 KHz), and the Late High Mult should be set to values significantly lower than 1.0X.
• Late Cross should be set higher than 0.0, in order to simulate the envelopment of real halls. Late Cross values less than 1.0 will help retain the spatialization of stereo inputs, so this should be tweaked according to taste – start at 0.5 and work your way up or down.
• The Early Mod Depth should be set to 0 for realism – higher values result in an unnatural panning of the early decay. The Late Mod Depth can be set higher than 0, and a little bit of modulation helps enhance the realism, but keep the Late Mod Rate in the 0.25-1.0 Hz range to avoid obvious pitch changes.

As a quick example, here’s a preset based on the measurements of Boston’s Symphony Hall, as described in Leo Beranek’s “Concert Halls and Opera Houses”:

<ValhallaRoom pluginVersion="1.0.5" presetName="SymphonyHall" mix="0.333000004" predelay="0.0671999976" decay="0.0180180185" HighCut="0.408053696" earlyLateMix="0.699999988" lateSize="0.74000001" lateCross="0.730000019" lateModRate="0.111111112" lateModDepth="0.720000029" RTBassMultiply="0.400000006" RTXover="0.0313131325" RTHighMultiply="0.533333361" RTHighXover="0.216778517" earlySize="0.0394394398" earlyCross="0.0299999993" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="1" diffusion="1" type="0"/>

A quick tweak of the above, with a change of the Reverb Mode from Large Room to Large Chamber (just to shake things up), and we have a model of Vienna’s Grosser Musikvereinssaal:

<ValhallaRoom pluginVersion="1.0.5" presetName="GrosserMusikvereinssaal" mix="0.425000012" predelay="0.0240000002" decay="0.0194194186" HighCut="0.371140927" earlyLateMix="1" lateSize="1" lateCross="0.709999979" lateModRate="0.103030302" lateModDepth="0.720000029" RTBassMultiply="0.433333337" RTXover="0.0909090936" RTHighMultiply="0.5" RTHighXover="0.258389264" earlySize="0.0441441424" earlyCross="0.0299999993" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="1" diffusion="1" type="0.333333343"/>

It is worth noting that I haven’t been to either of the above halls in person, so take the above presets as a rough starting point for creating your own concert hall presets.

ValhallaRoom Tips and Tricks: Short Drum Rooms

ValhallaRoom can be used to generate a room sound that works well with acoustic drums. Some recommending starting points:

• Use the Large Room or Large Chamber Reverb Mode. These provide an earlier onset of echo density.
• Dial in the initial “size” of the room with PREDELAY. A standard trick is to use 15 to 30 milliseconds of predelay for the ambience mikes in a “live” drum room.
• DECAY should be set anywhere from 0.3 seconds to just over 1 second.
• HIGH CUT can be used to tame the high frequencies of the decay. A real room is often much darker than one would think, so don’t hesitate to set this as far down as 5000 Hz. A brighter room can be set between 6 and 9 kHz.
• The DEPTH control is used to dial in the ratio of early to late energy. A setting of 50% is a good starting point.
• The Early Size setting can be used to add a short amount of early reflection energy to the attack when set to the 10-30 msec range. A setting of 50 to 100 msec is useful in obtaining a slight amount of “gated” sound, or for simulating the flattening of the decay envelope produced by heavy limiting/compression or tape saturation. Note that the overall decay time will be extended by the Early Size setting.
• The Early Send control is critical in shaping the early attack of short room sounds. By setting Early Send to 0.0, the initial attack can be varied between flattened and an exponential decay, by adjusting the DEPTH control to crossfade between the Early and Late reverbs. With Early Send set closer to 1.0, the Early Size setting will dominate the decay of both the Early and Late reverbs, producing a flattening of the initial decay.
• The Late Size should be set to 0.5 or less, to produce the highest initial echo density.
• The Late Bass should be set to 1.0X or less. Lower values add clarity to the decay.
• In general, a more realistic room sound is obtained by keeping the Early and Late Mod Depth set to 0.0. However, if you are wanting to emulate the super chorused “room” of the EMT250, by all means feel free to crank the Mod Depth up!

A few example presets (copy to your clipboard, and select “Paste from clipboard” in the Preset menu to hear the sound), starting with a realistic small room:

<ValhallaRoom pluginVersion="1.0.5" presetName="SmallishDrumRoom" mix="0.300000012" predelay="0.0299999993" decay="0.00300300308" HighCut="0.530201316" earlyLateMix="0.5" lateSize="0.330000013" lateCross="1" lateModRate="0.0909090936" lateModDepth="0" RTBassMultiply="0.153333336" RTXover="0.0909090936" RTHighMultiply="0.444444478" RTHighXover="0.530201316" earlySize="0.0193193201" earlyCross="0.100000001" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="0" diffusion="1" type="0"/>

The next preset generates more of a compressed/gated early attack:

<ValhallaRoom pluginVersion="1.0.5" presetName="SmashedDrumRoom" mix="0.300000012" predelay="0.0299999993" decay="0.00300300308" HighCut="0.463087261" earlyLateMix="0.5" lateSize="0.49000001" lateCross="1" lateModRate="0.0909090936" lateModDepth="0" RTBassMultiply="0.153333336" RTXover="0.0909090936" RTHighMultiply="0.444444478" RTHighXover="0.530201316" earlySize="0.067467466" earlyCross="0.100000001" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="0" diffusion="1" type="0.333333343"/>

By setting the Early Send parameter of the previous preset to 1.0, the early attack is extended, to produce a bit of a slapback echo effect.

<ValhallaRoom pluginVersion="1.0.5" presetName="SlapbackDrumRoom" mix="0.300000012" predelay="0.0299999993" decay="0.00300300308" HighCut="0.463087261" earlyLateMix="0.5" lateSize="0.49000001" lateCross="1" lateModRate="0.0909090936" lateModDepth="0" RTBassMultiply="0.153333336" RTXover="0.0909090936" RTHighMultiply="0.444444478" RTHighXover="0.530201316" earlySize="0.067467466" earlyCross="0.100000001" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="1" diffusion="1" type="0.333333343"/>

ValhallaRoom Tips and Tricks: Gated Reverbs

Generating a gated reverb sound with ValhallaRoom is easy:

• Set the DEPTH control to 0%, so that only the Early reverb is heard.
• Set PREDELAY to 0.0 msec, so that the gated sound is generated by the Early energy only (the PREDELAY can be set higher for gated echos).
• Set Early Diffusion to 100%, for maximum echo density.
• Use Early Size to dial in the desired gate length in milliseconds.
• Adjust High Cut for desired brightness
• Use Early Mod Rate and Early Mod Depth to add chorusing to the gated reverb sound

Here’s a preset for a 150 msec gate. Copy the entire text, including the < and > tags at the beginning and end, and use the “Paste from clipboard” option in the Presets menu to bring the preset into ValhallaRoom.

<ValhallaRoom pluginVersion="1.0.5" presetName="Gate150msec" mix="1" predelay="0" decay="0.0190190189" HighCut="1" earlyLateMix="0" lateSize="0.5" lateCross="1" lateModRate="0.0909090936" lateModDepth="0.5" RTBassMultiply="0.333333343" RTXover="0.0909090936" RTHighMultiply="0.444444478" RTHighXover="0.530201316" earlySize="0.14914915" earlyCross="0.119999997" earlyModRate="0.0909090936" earlyModDepth="0" earlySend="0" diffusion="1" type="0"/>

ValhallaRoom: The Late controls

The Late reverberation controls in ValhallaRoom can be accessed by clicking the Late button under the VALHALLAROOM title at the top of the plugin. The Late button will turn red when the Late editor is active.

An overview of the Late reverb controls:

• Late Size: adjusts the relative size of the late “room.” Larger values correspond to larger spaces, and will result in a more expansive sound. For some of the Reverb Modes, high settings of Late Size will result in audible early echos, so adjust this by ear for each reverb mode.
• Late Cross: controls the amount of coupling between the reverberators for the left and right channels. A Late Cross setting of 0.0 corresponds to separate reverbs for the left and right channels, where a signal injected into a single channel will decay in that channel only. Increasing the Late Cross setting will cause energy to spread across the stereo image as the signal decays, at a rate determined by both the Late Cross setting and the Late Size control (with a smaller setting of Late Size corresponding to a faster spread of energy between the left and right channels). By setting Late Cross to a value less than 1.0, the input stereo image will be preserved as the sound decays away.
• Mod Rate: controls the modulation rate of the Late reverb. This is more of an “average” rate, as there is a LOT of modulation going on in the Late reverb, with up to a few dozen LFOs, all of which are randomized and have different base frequencies. Generally speaking, rates around 0.5 Hz are useful for smoothing out any artifacts in the decay, while rates above 1 Hz are useful for adding lush chorusing artifacts.
• Mod Depth: controls the depth of the modulation in the Late reverb. Note that this is also dependent on the Reverb Mode setting, with the Bright Room having more obvious random pitch warbles for a given Mod Depth settings than the other modes.
• Bass Mult: adjusts the decay time for the low frequencies, relative to the mid frequency decay time set by the DECAY slider. Examples:
  • A Bass Mult setting of 0.5X, and a DECAY setting of 2 seconds, will result in a low frequency decay time of 1 second.
  • A Bass Mult setting of 2.0X, and a DECAY setting of 2.0 seconds, will result in a low frequency decay time of 4 seconds.

  From a physical perspective, Bass Mult settings >1.0X are useful for emulating halls and other large spaces, while Bass Mult settings <1.0X can be useful in emulating smaller spaces. From a perceptual perspective, Bass Mult settings greater than 1.0X add more “warmth,” while settings less than 1.0X create “clarity.”

• Bass Xover: controls the crossover frequency, in Hertz, between the bass decay (which is controlled by Bass Mult times DECAY) and the midrange decay (which is controlled by DECAY). Generally speaking, this is most effective when set somewhere between 300 Hz and 1500 Hz, but values outside of this range are useful for special effects.
• High Mult: adjusts the decay time for the high frequencies, relative to the mid frequency decay time set by the DECAY slider. Examples:
  • With High Mult set to 0.25X, and a DECAY setting of 2 seconds, will result in a high frequency decay time of 0.5 seconds.
  • With High Mult set to 0.5X, and a DECAY setting of 2.0 seconds, will result in a high frequency decay time of 1 second.

  From a physical perspective, high frequencies tend to be absorbed by air fairly rapidly, so setting High Mult to 0.5X or less will result in a more natural decay. From a perceptual perspective, use High Mult to control the brightness or darkness of your reverb decay to your tastes.

• High Xover: controls the crossover frequency, in Hertz, between the the midrange decay (which is controlled by DECAY) and the bass decay (which is controlled by Bass Mult times DECAY). For normal settings, values between 3000 Hz and 8000 Hz are useful, but this is highly dependent on the High Mult factor, as well as the desired effects.