TreeVerb Wooden Plate Reverb
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by Barry Rudolph
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A happy marriage between electromechanical technology and nature brings into existence TreeVerb™, a plate reverb that uses a single sheet of aged wood instead of a metal plate.

The brainchild of Bill Mareci of Audio Rents in L.A., TreeVerb was the result of a research and development effort based more on contemplative thought than empirical data collection.

Audio Rents' Bob Burton explains: "With the economic downturn, it was a slow day at the shop last week so both Bill and I found ourselves with nothing to do but 'plant' the seeds of TreeVerb."

When you consider that guitar-makers prize and harvest certain species of trees known as "tone woods," it makes perfect sense that a good solid piece of the right wood would make an excellent medium for sound reverberation.

The TreeVerb In Action In The R&D Lab Of Audio Rents, L.A.

From Small Acorns Grow Giant Oaks

Germinated from experiments with a NXT Transducer, TreeVerb started as a 4-foot by 8-foot wood panel sheet speaker suspended by short springs from a surrounding steel frame.

Finding this interesting, Mareci then used a doctor's stethoscope to find the "sweet spots"--where the sound vibrating through the wood seemed to build up and sound the best. At that spot and one another, contact mics were attached and connected to a conventional two-channel mic pre-amp.

"Getting a useable reverb sound out a piece of wood is no small task," says Mareci. "My research revealed ingrained problems I had overcome by using special audio processing of both the audio signal sent into the TreeVerb as well as the recovered audio coming back off the wood."

Signal Processing

A special pre-emphasis processor for the audio "send" signal was developed using the patented CCCC technology. CCCC, or Cellulose Compression Curve Compensator™, pre-conditions and expands the audio so that it propagates through the wood in the most liberated and natural way.

Furthermore, since any remaining pockets of sap left (after kiln drying) can be detrimental to the high frequency response of the reverb's decay, a special dynamic Sap Suppressor or Sappressor™ is used to counteract the capillary action of any granularly whorls.

NXT Transducer
The TreeVerb's NXT Transducer
The returned signal from the TreeVerb must be processed for two significant reasons. The restricted frequency response of the contact mics is reversed and the effects of the inherent and variable K Factor are ameliorated. K Factor, caused by the non-linear distortion of random knots in the wood, is corrected with the Knot Equalizer™. The K EQ is a discrete, phase-linear, all Class-A, transformer coupled module that is "tuned" to the specific wood type used. Generally harder woods like oak or mahogany require less K EQ while softer woods such as ash or pine may require as many as three branches of K EQ.

TreeVerb Sapling
The Early Days Of TreeVerb
TreeVerb, although still at the production prototype stage, will be available using a variety of exclusive eco-friendly tone woods. The first additional model to be released after the inaugural Sequoia model will be the Salsa Arriba constructed using only selected avocado wood. Other 'sonic veneers' in development are: The Floater model using only balsa wood for the lightest sound and for heavier Rock music, the mahogany ThunderRose model.

Finally, for user customization, Dynamic Limb Library (DLL) technology is included to store presets of parameter sets for the CCCC, Sappressor and K Equalizer.

OK So What Does A Wood Plate Reverb Sound Like?

My first test was using TreeVerb used as a drum reverb. We played different drum kit recordings in Pro Tools HD and sent them to TreeVerb. A BGW power amp drives the NXT driver and a Jensen mic pre-amp is used for the contact mics' return signal.

The sound is a short reverb with a certain coloration that's unmistakable wood-like. Boxy sounding by design, it is similar to a shorten Small Wood room preset on a high-end digital reverb. The two contact mics spaced far apart on the sheet of wood provide a stereo image effect that I've not heard before in any reverb. It's of a more noticeable phasey nature. It's a great effect that could work for all sorts of sources--vocals, electric guitars, keys, and percussion.

It's early days for TreeVerb and the future looks bright for this technology to become a truly professional piece of gear. I want to stay tuned! Mareci says: "I was thinking of offering a kit for sale for anyone interested. Essentially it would consist of everything you need and the customer would supply the sheet of wood."

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