SAM effects

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The following was posted on the Linn Forums site by a Linn engineer, by way of an explanation as to how SAM works and contrasting it to the Linn Exakt system:


"The Devialet SAM system functions as a bass extension filter. They match a shelving filter that is equal and opposite to the natural roll-on of the speaker(*), effectively pushing the low frequency response of the speaker down in frequency. The shelving filter will produce an equal and opposite phase response to the natural roll-on of the speaker(*) thereby linearising the low frequency phase response (to some degree).


(*) based on measurement of a single loudspeaker, so not truly accurate when you consider production variance.

At very low playback levels this extension can be pushed to (conceivably) quite low frequencies without end stopping the drive unit. However, as playback level is increased, the influence of the shelving filter applied by Devialet is reduced giving progressively less bass extension as the volume is increased. To claim that the low frequency of the Ninka is extended to 15 Hz is therefore rather disingenuous.
..."

Guillaume

That's very interesting.  It makes it sound as if SAM is going to compress dynamic range in the bass region, which surely can't be right, can it?  If it works like that, is the extent of the SAM effect actually controlled by the volume setting (static) or the average "loudness" of the signal (dynamic)?