# How to calculate viscous damping properties of air in loudspeaker design

1. May 31, 2009

### thadman

In the design of a loudspeaker, one intuitively seeks a critically damped alignment. We must consider the electrical resistance of the coil, magnetic field strength, mechanical resistance, mechanical compliance, and mass (diaphragm + acoustic load) of the system.

The electrical resistance, magnetic field strength, and mass of the system are easy to calculate and verify. The mechanical resistance and compliance are more difficult.

If the design uses an acoustic suspension (ie enclosure), we must consider the compliance and resistance of the air within the enclosure.

I believe the linearity of the compliance of the air can be calculated from the derivative of PV=nRT.

However, I'm unsure how to calculate the resistance (viscous damping, correct me if I'm wrong) of the air within the enclosure.

Thanks,
Thadman

Last edited: May 31, 2009
2. Jun 2, 2009

### thadman

Is this the wrong section?

3. Feb 19, 2010

### neurosport

Simple - ignore it.

Air viscosity is zero unless you're dealign with very small apertures.

If viscosity of Air was significant it wouldn't cost thousands of dollars to treat studios with acoustical foam.

You know you can always make theory more and more complex and accurate. You can model the motion of every subatomic particle in your loudspeaker - but why ?

Listen to Geddes - there are plenty of real problems to solve before you start inventing ones to keep yourself busy.

Last edited: Feb 19, 2010
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