AES Section Meeting Reports

Pacific Northwest - June 18, 2015

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Sean Costello of Valhalla DSP was the featured speaker at the PNW Section June 2015 meeting and election. Valhalla DSP is a developer and online source of software plugins for Mac and Windows based audio editors. Sean talked about the history of artificial reverb, some classic reverberators, and some algorithms. There were 18 AES members (sufficient for quorum) and 18 non-members in attendance, allowing election of the 2015-16 PNW officers and committee.

Sean started out experimenting with Csound at the University of Washington in the late 1990s. He was hired by Staccato Systems in 1999 and worked developing physical models for video games. Staccato Systems was acquired by Analog Devices in 2001 and he began working on audio algorithms and development tools for the SHARC and Blackfin DSPs. In 2007, he began working as a consultant, developing a wide variety of audio algorithms for a variety of clients. He started Valhalla DSP in 2009 with the release of ValhallaFreqEcho. Sean approaches algorithms from a psychoacoustic perspective and enjoys creating and selling tools directly to artists.

Although Sean's focus is digital reverb algorithms, he began the talk with a light overview of how reverb has been defined, and what reverb was before artificial reverb (concert halls, rooms, echo chambers). He also covered some characteristics of these types of reverbs. After this, he touched briefly on spring and plate reverbs, some of the defining auditory characteristics of them, and why they were such an innovation at the time.

He then dug into artificial reverbs, starting with the Schroeder algorithm, which was a published algorithm. He then focused on a few classic reverbs from the 1970s, most notably, the Lexicon 224, the EMT 250, as well as some of the characteristics of these reverbs, due in large part to the hardware limitations. We were fortunate enough to be joined by Rene Jaeger, who worked at Lexicon and shared some anecdotes.

Next, Sean spoke about reverbs from the 1980s, and some of the advancements that were made in this time. In particular, how reverbs were no longer being used for "natural" sounding treatments, and creative reverb algorithms became prevalent. Sean then discussed many popular reverbs developed during the 1980s highlighting some of the unique characteristics of each.

Sean illustrated examples of what you might expect from some of these early reverbs by way of Valhalla DSP emulations of his own design.

Finally, Sean delved into what he refers to as the, "The Reverb Grimoire" (Book of magic spells and incantations) — the fact that many digital reverbs were (and are) developed in secret and little published information exists. He discussed some information that has become available on classic reverbs and some of the early reverb "gurus".

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