Level-dependend Sound Quality by certainly Bass Drivers - very bad sound at low level - diyAudio
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Old 1st April 2010, 07:31 PM   #1
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Default Level-dependend Sound Quality by certainly Bass Drivers - very bad sound at low level

Over the years I observe always very bad sound in the low level sonic aera by certaily material of the surround - mostly certainly kind of rubber material. All this loudspeakers have in most (not in all) cases a low value of mechanical quality (parameter: Qms).

If I measure the parameters, I observe also level independend so as temperature independend Thiele Small parameter variation for Fres, Qms, Qes and Vas, except in such cases, where the low QMS value caused only through aluminium shortening ring on the voice coil and copper capped pole piece.

For my subwoofer and loudspeaker projects I use therefore mostly cloth surrounds or foam surrounds. Here I haven't above mentioned unwanted effects. There are very few rubber surounds with level and temperature independend behaviour. The KEF B110A-SP1003 or the various types of PHL's B17 series are good examples. Bad examples through the selected rubber material for surround are certainly models of the Dynaudio drivers (at least that types from the Contour series, that I know).

The parameter Qms and thus Rms consists of a nonlinear (level-dependent) component and a linear (level independent and temperature independend) component.

The linear component causes through aluminium shortening ring so as copper capped pole piece - e. g. Peerless HDS182 about
http://www.d-s-t.com.au/data/Peerless/850467.pdf

And the non linear (level-dependent) component causes through the rubber material of surround or - if cloth material used - the material of impregnation and its behavior at different strains und different temperatures (by the spider only the material of impregnation and its behavior).

Which measuring methods exist today for loudspeaker chassis TSP measurement, to determine isolated these two influence factors for the parameter Qms resp. Rms?

Thank you for your comments
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Old 2nd April 2010, 04:12 AM   #2
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Do a search for mige0's comments on driver friction---I think they're in StigErik's "my open baffle with Beyma 150TLP build" thread but am not sure. Michael posted some measurements of driver static friction. In his "beautiful swingin' speaker" thread there's more discussion of linen surrounds and high Qms/high VAS/low Rms drivers.
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