Air Resonance

[davidross]

Could someone just briefly explain the significance of a driver's air resonance? What role does it play in a driver's performance?

[planet10]

Free air resonance?

Where a driver's mass & its compliance form a spring resonanance.

dave

[davidross]

Dave, thank you. Can you tell me what areas of a driver's performance that affects?

[Scottmoose]

I'm not Dave, but the blunt answer is just about everything, in the same way that it is equally a consequence of other driver characteristics. It's just one of many factors, and the value of focusing upon it in & of itself is somewhat limited.

[davidross]

I think I see what you mean, that air resonance alone is not a good predictor of a driver's behavior or performance. So just to finish up with this, does that mean if one driver's air resonance is 35hz, for example, and another's is 90hz, it's not possible to make inferences about how those drivers' performance differs in any area? For example, do those values suggest anything directly about frequency coverage?

[Scottmoose]

Other than the obvious fact that one nominally goes lower than the other & is therefore possibly of more use as, say, a bass driver, no. Otherwise, Fs alone tells you almost nothing about the unit.

[planet10]

Originally posted by Scottmoose
Fs alone tells you almost nothing about the unit.

Fs, Qts, and Vas together do allow you to use simple modelers to generate sealed & vented box alignments.

dave

[Scottmoose]

One down, two to go...

[davidross]

Thanks very much, guys.

[rjbond3rd]

David, speaking strictly as a newb, try this simplistic little experiment. Take a driver, not in any cab, play various frequencies through it using a little software tool (e.g. the tone generator from Marchand Electronics, or by making tones in Audacity, or via a test tone CD).

Use low volume, obviously! Note what happens when the frequency is around Fs. The cone starts to behave a little strangely. It may flop around wildly. The driver as a total system is now operating at its point of resonance in free air, and it's "resonating" and not making much music.

See if you can play any tones lower than Fs. Then you can probably see why simple cabs don't generally try to play lower than Fs (ignoring for a moment that driver + cab can lower the Fs compared to free air, because the cab can "damp" the cone by putting pressure on the cone's back which can lower Fs).

If yo uhave an impedance / frequency response plot from the manufacturer, or another source, look at what happens to impedance as it approaches, and reaches, Fs.

Now imagine how Fs would change if, for example, the magnet's strength was greater or weaker (Qts), or if the suspension was stiffer (Vas). Imagine if the cone were heavier -- what would happen to Fs? E.g., if you put a penny on the cone? You can try that. You're just trying to get a feel for the driver as a system of multiple interacting parameters.