An Engineer's Perspective

How to Catch a Wave

More than a decade ago, as Legacy began a tour of road shows debuting new audio and home theater products, we would have to set up in different venues each week.  Rooms varied from ballrooms to hotel conference rooms and suites, and acoustics varied considerably. The real challenge was to generate a sweet spot that would serve more than a dozen listeners at a time.

Typically, we would set up the Legacy Whispers spread quite wide with a strong toe-in, then position the Focus speakers to the inside of them in the same plane. This allowed listeners to comparatively experience the systems without relocating themselves or the speakers.

While we could dictate the seating positions and speaker locations, we certainly could not dictate the distribution (position, frequency, or amplitude) of standing waves that would develop in a given room*. Whisper with its narrower and more controlled low frequency radiation generated and propagated a more useful pattern over the length of the room and offered an extra degree of room independence.  It also benefited from the Whisper analog processor which could be set for listener proximity. So helpful was this control, that within a year the STEP One (Stereo Environment Processor) was born to assist the Focus system. This unit was factory adjusted for the typically floor to ceiling axial resonance (71 Hz) for those with 8 ft. ceiling heights.

In the decade that has passed**, Legacy has continued to pioneer the methods of treating boundaries and reflections in the listening room (the reader may elect to read further about what I refer to as the Three Rs of listening room acoustics; REINFORCEMENT, RESONANCE, and REVERBERATION***.)

By William R. Dudleston

Obviously we would like a speaker system to cover the broadest possible frequency range, have minimal response  deviations, sound clean at any reasonable listening level and not be a slave  to room placement. But how do we get there from here? We can start by examining some basic principles of loudspeaker design.

by William R. Dudleston

I recall a very interesting conversation with Dr. Belle  Julesz, Research Director of Psychoacoustics at Bell  Laboratories for 35 years. This remarkable man came to  understand more about the human hearing mechanism  and the way the brain localizes sounds than anyone on this planet.

Somehow, we got into a lengthy discussion about  how a barn owl rotates its head to triangulate the  location of mice in the dark. We then related this to  human hearing and localization of sources of sound. It  seems that we, like the barn owl, tend to turn our  heads a bit when we hear an interesting sound. Our  brain wants to “view” things at a different angle to try to assign positional coordinates to the sound.  Sometimes this rotation of our heads is obvious, most  of the time we don’t even notice. Yet, these subtle  rotations allow us to “lock-on” the apparent source of a sound.

Which pro do the record labels trust to remaster some of the greatest recordings of all time? Steve Hoffman of course. Steve chose the Legacy Whisper system as his reference at DCC Compact Classics.  “Whether it’s the velvety croon of Nat “King” Cole, for the screaming guitar of Eddie Van Halen, Whisper reveals what I call The Breath of Life; the very essence of these recordings.”

by William R. Dudleston

“My goal with Whisper® was to create the most undistorted mirror of the microphone to date. Whisper was built in prototype stages using electrostatic, ribbon, Heil and and moving coil transducers. The speaker that resulted represents our best efforts and has remained essentially unchanged over the last three years. I have resisted any and all temptations to flavor the design. In short, this speaker is selfishly designed to satisfy a very personal goal.

Being a life-long recording technique fanatic*, I literally wanted Whisper to be able to discern the differences between a Schoeps-Collette, AKG 414 or  Neumann U-47 microphone in application. 

To test Whisper for coloration in the design phase,  I would literally play a solo performance through  Whisper and re-record it as a live event using comparable  mic technique. This in turn would be played back  and re-recorded again. Such a process is brutally  revealing of any colorations and room dependencies. I  have learned more with PROJECT WHISPER than any  other project in which I have been previously involved  and feel grateful for the acceptance Whisper has  received in recording studios around the world.”

GRAMMY AWARD WINNING PRODUCER—RICK RUBIN

American Recordings producer Rick Rubin made Legacy’s FOCUS his personal choice.

Rick Rubin produced Mick Jagger’s “Wandering Spirit” and Tom Petty’s critically acclaimed “Wildflowers”. Rick also orchestrated Run DMC/Aerosmith’s “Walk This Way”, one of the most influential video performances in pop history.
In 1997 Rolling Stone’s critic’s poll voted him “Best Producer”.

“As a Mastering Engineer, I choose my tools very carefully. I rely on the Legacy Whisper, FOCUS and Studio speakers for all phases of post production in the studio. When clients ask how I make everything sound so good, I just tell them it’s magic, and that magic is Legacy!”

-Bob Pantages, Hideaway Studios

by William R. Dudleston

Through the years of qualitatively evaluating loudspeaker  designs, I have employed a simple quantitative  method for measuring a loudspeaker system's ability  to maintain signal correlation between channels in a  reverberant field. I have labeled this empirical indicator  the IMAGING INDEX. This method can also be used to  fine-tune speaker/listener relationships within a listening  room to achieve optimal stereo imaging. It requires  little more than a sound pressure level meter and pink  noise as a source.  But first some fundamentals should be acknowledged.

In The Lab, by William Dudleston 

“For many years the listening room has been regarded by speaker designers as the great unknown; a set of variables involving room geometry, absorption coefficients and decay patterns. Designers have attempted almost as many solutions to room problems as there are rooms. Dipolar, bipolar, cylindrical, omni-directional, and highly directional radiators to name a few. Electrostatic, moving coil dynamic, ionic, planar dynamic, thermo- dynamic and even plasmic transducers.

Read more: Fundamentals of the 21st Century