We all now have to use the phrase “the award winning plugin, Eos”

I just found out that Eos won a Sonic Joy Award for 2009, from the AudioNewsRoom blog. So, Eos is now “Audio Damage’s award winning plugin, Eos,” or simply “the Award Winning Eos” for short. Take note, and please use some variant of the above in all future references.

On a related note, I am now referring to myself as “The DSP Situation,” in the 3rd person. It’s all about the algorithm abs. Again, please take note of this for all future communications.

Seriously, it feels pretty nice to be involved with the design of an award-winning plugin. I hope 2010 brings more good things like this.

Merry Christmas

To celebrate the season, here’s a few sloppy guitar tracks of mine from 2003:

Joy To The World

The First Noel

Silent Night

For those you feeling less festive, here’s some Csound work from 1998:

otis

The “score” was done with a combination of Common Music and Notepad.

Finally, here’s a few random pieces from 2003, when I was playing around with Reaktor, Ebows, Moogerfoogers and harmonicas:

there’s a little beating heart

first thing i recorded on ibook

Happy Holidays.

Eos tips and tricks: Recreating the PCM70 Tiled Room

One of the “greatest hits” of artificial reverbs is the Tiled Room preset in the V2 ROM of the Lexicon PCM70. This preset went missing from the V3 software, but you can find a listing of the parameters here.

I was playing with an impulse response of this preset, and decided to emulate it in Eos. Here’s what I came up with:

• Type: Plate 2. For maximum authenticity, you could use Plate 1, as both Plate 1 and the Rich Chamber algorithm used in the PCM70 Tiled Room preset have a mono input. However, Plate 2 works better with stereo miked material.
• Pre-Delay Time: 4 msec. This is the same as the original Tiled Room preset. If you wanted to simulate a somewhat bigger space (or the delayed room mikes used by many engineers, such as Steve Albini for The Jesus Lizard’s “Goat”), you could set this between 15 and 30 msec.
• Size: Try setting this between 10 and 20 meters. The PCM70 preset used 8 meters, but this might have been an attempt to get a more exponential decay out of the Rich Chamber algorithm, which has a fairly “flat” decay compared to most acoustic spaces. The Plate algorithms in Eos will always decay away exponentially, so Size can be used to control the apparent size of the room, as well as the desired coloration.
• Attack: Set this fairly low.
• Diffusion: I used 0.5. For drums, you may wish to increase Diffusion, while vocals might require lower settings to avoid metallic coloration. This is true with the Lexicon as well, and seems to have something to do with the pulsetrain waveform of vocals. The Plate algorithms in Eos have a fairly high initial echo density to begin with, even with lower settings of Diffusion.
• Decay: 0.62. Same as the Lexicon.
• Low Multipler: 1.258. This results in the same running decay time as the Lexicon
• Low Crossover (accessible in the automation view in some programs, and the Controls View in Logic): 3410 Hz.
• High Multipler: 0.25. The Lexicon Rich Chamber algorithm uses a one-pole lowpass filter, as opposed to the 1st order shelf in Eos, so setting the High Multiplier to 0.25 better emulates the steeper rolloff of the Lexicon
• High Crossover: 9000. This is pretty high, but it emulates the setting in the Tiled Room preset.
• High Cut: 10000 Hz. I would probably set this lower as needed. The PCM70 has a hard cutoff of 15 kHz, so you may wish to lower the High Cut setting to compensate for this.

The other settings have no corresponding settings in the PCM70, so adjust for taste:

• Low Cut should be used to eliminate any unwanted “booming” of the bass frequencies.
• Mod Rate and Mod Depth aren’t relevant to emulating the Tiled Room preset, as the Rich Chamber algorithm in the PCM70 didn’t have modulation – but if you like the sound of modulation, go for it. Smaller Size settings will result in more apparent modulation.
• The stopped reverb decay will be shorter on the PCM70 than in Eos (or in the PCM70 impulse responses), as the PCM70 has separate decay settings for stopped reverb, so adjust the Eos decay time as needed to strike a good balance between running decay and stopped decay.

DSP Hero: Robert Bristow-Johnson

Super nerdy DSP content warning.

If you program audio DSP effects, you have undoubtedly heard of Robert Bristow-Johnson. If you haven’t heard of him, get yourself a copy of his Audio-EQ Cookbook. This is a succinct little document, that provides coefficient generation formulas for pretty much any second order filter building block you would ever need: lowpass, highpass, allpass, peak EQ, notch, shelving filters, etc. Today, I am implementing these formulas for my own code, but I know I’ve implemented them in at least 3 prior DSP environments. Really good stuff.

A quick Google search doesn’t turn up a ton on Robert Bristow-Johnson (or RBJ, as he is often abbreviated). He worked at Eventide, Fostex, Young Chang (Kurzweil), and Wave Mechanics. RBJ has a few AES papers as well, all of which are worth reading, covering topics ranging from PSOLA pitch shifting (made famous by AutoTune) to filter design to interpolation for oversampling.

If anyone out there knows RBJ, send him my thanks!

A reverb paper of mine just got published online

I wrote a paper with my old coworker and friend Joseph Anderson on reverb architectures for Ambisonics. You can download the paper here.

It was a lot of  fun writing a paper with Dr. Anderson, who is also a master of writing compositions that use Ambisonics to nice effect. Joe (ok, I call him Joe) manages to make Ambisonics work beautifully. One of his compositions uses a salad bowl spinning around a SoundField microphone, which is a very expensive way of getting a simple effect, but the results are stunning when heard in an Ambisonics environment.

ValhallaFreqEcho AU updated. Less crashy!

I just posted an update of the ValhallaFreqEcho Audio Unit, that should fix some bugs people were encountering with Logic. The plugin assumes stereo-input, stereo-output, but the older version of the AU wasn’t enforcing this. I changed the code so that it can only be instantiated on stereo tracks. I will work on having it run with mono tracks in a future release.

Download the new version of the code here.

Musical example of ValhallaFreqEcho feeding upon itself

Barry Stramp just posted a quick soundfile made with ValhallaFreqEcho to Gearslutz:

avoidance

I really like this piece. It sounds similar to some of the things that I have running late at night using ValhallaFreqEcho, but with far more compositional chops going on.

ValhallaFreqEcho updated: new controls, VST+AU

I just posted some updates to ValhallaFreqEcho, my free frequency shifter + analog echo plugin. You can download the plugin here. The new stuff:

• New parameters: Low Cut and High Cut. These control the gain of shelving filters in the feedback path of the echo (the direct and initial echo signal are not filtered). These controls are very useful in getting different type of analog sounding echos, as well as harsher or flubbier echos, plus a variety of strange chaotic oscillations.
• An Audio Unit version of the plugin is available, in addition to the VST plugins for Windows and OSX.

I’ll be posting some usage tips soon. I have spent a lot of time setting up runaway oscillations with the plugin, using no input (it self-oscillates like the old analog echos). Some very trance-y sounds can be coaxed out of this thing – not the dance music type of trance, but the “staring into space and drooling for awhile” type of trance.

Eos review in Computer Music: 9/10

The first magazine reviews are rolling in for Eos. Computer Music gave it a 9/10. Interestingly enough, they liked the Plate algorithms more than Superhall.

Full review here.

Their verdict: “A stunning vintage-style digital reverb at a price that makes it an essential purchase.”

More general reverb tips

As a followup to my Eos tips and tricks post, I thought I’d share some more reverb tips. All of these have been tested with Eos, but should also work with a wide variety of hardware and software reverbs.

• Set the high cut filters to a fairly low frequency. Older hardware reverbs, such as the EMT250 and Lexicon 224, had a hard cutoff at 8 KHz to 10 KHz, due to the low sampling rate of the machines. The high cut filters in many reverbs have a much more gentle slope than the high order filters used at the inputs of these old boxes. To emulate these old boxes, try setting your high cut filters to a fairly low frequency, such as 2 to 4 KHz. This also corresponds more closely to the absorbtion of high frequencies by air in a large space, such as a concert hall.
• Use the low cut controls to make the reverb sound less “tubby.” Many concert halls actually have a much longer decay for low frequencies than mid range frequencies. This is useful for classical music, but for most popular music forms, the amount of bass energy that is present will sound flubby when reverberated. Set the low cut controls at 200 to 400 Hz, or even higher, for a clearer reverb sound.
• If you don’t have low or high cut controls, put the reverb in a send bus, and put the EQ of your choice before or after the reverb.
• Try compressing the input or output of the reverb, for some neat sounds. A limiter before the reverb will keep spikey transients from dominating the response, and will better emulate the transformer-coupled inputs of the old high-end hardware units. Compressing the output of the reverb will change the exponential decay response to something much weirder, depending on your settings.
• Plate reverbs have a lot of high frequencies in the decay, so make sure that the high frequency decay multiplier (or the high frequency decay filter cutoff) is set fairly high. These controls are usually separate from the high cut controls, that shape the sound at the input (or output) of the reverb.
• Adjust your modulation depth based on the decay. For long decays, you may wish to back off on the modulation depth, as the sound will travel through the modulators many more times compared to a short decay. Each pass through the modulators causes more detuning. A modulation depth that works for short decays may sound seasick for long decays. Of course, if that’s your thing, then go for it.
• Use the Size control for the desired echo density, but be mindful of how it affects the modal density. For example, if you want a small drum room, then set Size to a smaller setting, as it will make the echos closer together. However, a smaller Size setting will sound more metallic for longer decays, as the modal density goes down as the Size decreases. Longer delay lengths = higher modal density = less metallic = lower echo density. For short decays, the low modal density may not matter.
• The Size control is often given in meters. This has nothing to do with any real physical world metrics, in most cases. A real acoustic space with a 30 meter maximum dimension will have a few orders of magnitude higher modal density than your typical digital reverb with a 30 meter Size setting. Just tune it by ear to where you like it.
• Shorter Size settings may also result in deeper modulation for the same decay setting, so be sure to retune this for your tastes.

Hope these are useful to people. If you have any more tips, feel free to add them in the comments.