Det här kan man läsa på Harbeths hemsida: (stulet av paa)
I've heard mention of 'the BBC dip' or 'the Gundry dip'. What does that mean?
There is much myth, folklore and misunderstanding about the 'Gundry presence dip'.
The 'BBC dip' was a shallow shelf-down in the acoustic output of some BBC-designed speaker system of the 1960s-1980s in the 1kHz to 4kHz region. The LS3/5a does not have this effect, neither in the 15 ohm nor 11 ohm, both of which are in fact slightly lifted in that region.
According to Harbeth's founder, Dudley Harwood, who ran the BBC's design department during the time that this psychoacoustic effect was being explored, it was introduced initially to mask coloration in the vacuum formed cones available at the time. Whilst reducing speaker output in this audio band achieved this, it subjectively pushed the listener away from the speakers as the stereo-listener's sound stage subjectively receded behind the speakers, which is unobjectional for acoustic music, but takes the life out of non-classical music. An alternative strategy employed or in combination with the Gundry dip is the application of heavy glue (dope), usually by hand brushing, to the surface of the cone to ameriorate latent coloration. The Harbeth RADIAL™ cone has no coloration issues so does not need to use the BBC dip, nor cone doping, to disguise latent mechanical problems.
You can explore the sonic effect of depressing the presence band for yourselves by routing your audio signal through a graphic equaliser and applying a shelf-down in the 1kHz to 4kHz region
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Sonen till BBC-dippens skapare:
Well, of course having found this, I have to jump in. My father, Dick Gundry, who spent almost all his working life in the BBC and was for many years responsible for maintaining technical standards in BBC Radio (which have sadly gone down since his retirement in about 1971), and who was known behind his back as golden ears, would not have been pleased to have his name attached to a deliberate departure from a flat frequency response in loudspeakers. Has anyone any idea on how this term arose? It must have been much more recent than 1971.
One of my father's responsibilities back in the late 1950s and early 1960s was the development of stereo techniques in preparation for a means to broadcast it. (Some of those early experimental recordings have more recently been issued on CD by the BBC). At that time the BBC developed its own monitoring loudspeakers on the grounds that commercially available ones were generally not very good. I used to say that loudspeakers were either good or loud but not both! During early stereo experiments it became apparent that the best BBC monitoring speakers of the day did not perform well in pairs for stereo because they did not match each other closely enough, particularly in phase response, so central images tended to be diffuse. A major reason was that to accommodate variations in the drivers each and every cross-over network was adjusted for a flat amplitude response. A new range of speakers was developed, but it is possible that at least for those first ones, the uniformity was considered more important than perfect flatness, and thus the speakers may have shown the "Gundry dip". However it would not have been a design aim but a side-effect, and in any case my father would have had no input to the designs, which were developed at the BBC Research Department (Dudley Harwood, Spencer Hughes et al.)
Kenneth Gundry, San Francisco
https://hydrogenaud.io/index.php/topic,75195.0.htmlJM
Neuroscientist. Emotional Beauty is in the Ear of the Listener. "Kill your darlings" => scientific evolution.