6 Jan 2010

The Siegfried Challenge

David Clark

At the past few AES Conventions, Siegfried Linkwitz has presented papers claiming to have achieved near-perfect sound reproduction in an ordinary room with stereo source and speakers. In his latest paper he challenges the AES to study this illusion scientifically to determine optimum playback parameters. The AES does not directly do this kind of thing, but there might be members or their companies who would take it on.

I ran the idea past the SMWTMS hi-fi club and got enough interest to go forward. Siegfried is now on board with loaning a pair of his Orion speakers and helping with the design of the experiments. Competitive products and approaches will be included as well. Listening test sessions are planned to start late January 2010 and continue through March.

The basic concept of these experiments presumes that signal transmission, speaker distortion and frequency response can be sufficiently good that they need not be issues. The goal, rarely attained, is the creation of an Auditory Scene (AS) that is very close to that heard at the live performance. Listening room acoustics and loudspeaker’s interaction by directivity, off-axis frequency response and positioning are the variables to be studied.

The initial testing will be narrow in scope:

• Live, unamplified music and speech

• Commercial recording techniques

• Living room acoustics and speaker playback

• Two-channel stereo (upmix and multi-speaker playback may be tested)

• Listeners have recent live music experience

• Listeners have ability to evaluate using AS parameters, i.e. locations of phantom images

Two stages of testing are planned; a verification of the Existence of a plausible AS illusion and the Optimization of the illusion. The Existence test can only be sighted and will rely on auditory memory of live events in the subject’s experience. The tests will include the Linkwitz recommended speakers, positioning and acoustics. Optimization testing will involve repositioning and exchanging speakers behind an opaque screen and will be double blind. Optimization listening will be a comparison to a fixed reference in order to establish an anchor point and allow rapid comparison switching.

In conjunction with the Existence testing, we will have the opportunity to introduce alternatives to the Linkwitz Labs, Orion speakers. Also, we plan to use moderate-size box-speakers for the fixed reference in the Optimization tests.

We are looking for listeners who can spend a few hours of critical listening at David Clark’s house. We are also looking for the loan of best-quality speakers from manufacturers. These would be evaluated, behind the screen, as alternatives to the Orion speakers. Please contact me at dlc@dlcdesignaudio.com. More information is available at http://www.provide.net/~djcarlst/smwtms.htm