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Old 26th November 2004, 08:36 AM   #1
andy2 is offline andy2  United States
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Default What is "compliance" a driver or cabinet?

Could someone explain what "compliance" means physically?

What does it mean by "choosing a cabinet size having the same compliance as the driver"?
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Old 26th November 2004, 09:04 AM   #2
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In a nutshell, compliance is the stiffness. If a speaker has a compliance of 100 litres, then 100 litres of air will have the same stiffness when it is tried to be compressed.

You do not need to make the box size the same size as the driver compliance, that's ancient speaker design before they properly knew what they were doing.
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Old 26th November 2004, 09:30 AM   #3
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If you think of a bicycle pump. Put your finger over the mouthpiece and try to press the pump toghether. There it is. Complience.

If the enclused volume would have been larger - what would have happened? Well, it would have been easier to press it toghether. Less stiff.

Same for speakers. A speaker with lage Vas is the same as a bicycle pump with large volume. Not very stiff.

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Old 26th November 2004, 03:37 PM   #4
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Compliance is a technical term, still in use for technical papers.

You might see the compliance of the driver still listed in some places, with numbers like"1145MN-1" The minus 1 is in superscript. .

However, that is super technical talk. To bring it down to more useful terminology, "compliance" of a loudspeaker driver, while still listed in some places, has been replaced by the term "Vas". That is what you use for useful calculations.

Compliance of the box had been replaced by the term "Vb", or box volume. Their ratio, which you will see often, is given as "Vas/Vb".
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Old 26th November 2004, 04:40 PM   #5
Ron E is offline Ron E  United States
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Compliance is the inverse of stiffness. Compliance is in units of distance / force and stiffness is in units of force / distance.

If you have a volume of air that is being compressed by a piston it acts somewhat like a spring and teh force required to move it a certain distance is the stiffness of that volume of air, and the inverse of that number is the compliance.....

Vas is the volume of air that when compressed by a piston of the same diameter as the cone, would offer the same resistance as the cone does in free air.
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