Harbeth - designer's notebook

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Designer's notebook

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	Chapter 7 : Loudspeaker design: achieving a smooth image transition between left and right loudspeakers Pages: [4] - Current page: [3] Date created: 14 December, 2005 10:40 Comments: As illustrated on the previous page, certain colourations that bedevil loudspeakers can be interpreted by the brain/ear as changes in sound stage perspective. If these aberrations are severe, the listeners perspective is compressed to a binocular view, not a contiguous left-right spread. To forensically evaluate loudspeaker colourations, it is not good enough to rely on the human audio memory. A break in listening of even a few seconds is enough for the 'audio-DNA' to fade. Our ability to sense the environment is at it best when presented with comparatives: two shades of colour, two perfumes, two wines, two ties, two sounds. A remote control relay changeover box is an invaluable research tool for making these instantaneous comparisons between loudspeakers. The reason for the plethora of available loudspeakers with such a wide range of performance is a reflection of the accuracy and complexity of our internal mental-models of the real sound world. Our mental models and those of our users are more sophisticated and this reflects upon the design. Goto downloadable MP3 audio examples.

Fig 7-3A Remote control A-B switchover box

The white box is a home made relay changeover unit. Inside are many high quality relays that can be remotely controlled to flick the signal path between the banana sockets on the top panel virtually instantaneously. Out of picture to the left is the long remote control lead, which is hand held by the listener and he can operate the silent changeover switch at random.

Although this box can be used to compare two complete stereo pairs of loudspeakers side-by-side, in the configuration shown above, one pair of speakers (NRG2 on stands, not shown but at the end of the thicker white cables) is under evaluation at the crossover design stage. We have developed two 'breadboard' prototype crossover designs, X1 and X2, and although when simulated by computer these have a very similar frequency responses, we anticipated that there would be subtle differences in perceived quality - especially sound stage. The switchover box allowed us to critically evaluate these alternative strategies without relying on our memory, and to select the most natural sounding crossover that gave the widest, most involving sound stage.

Harbeth Audio Ltd., 3 Enterprise Park, Lindfield, Haywards Heath, W. Sussex, RH16 2LH, UK

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