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Old 31st December 2008, 08:35 PM   #1
MCPete is offline MCPete  United States
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Default lowering Qts

Dickason in his LOUDSPEAKER COOKBOOK says that Qts of a driver can be lowered by stretching porous fabric over the rear of the basket of the driver.

Does anyone know what type of fabric can be used, how to attach it to the basket of the driver and to what extent Qts can be lowered by doing this?

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Old 31st December 2008, 09:13 PM   #2
gedlee is offline gedlee  United States
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Since the vast majority of Q is electro-mechanical lower the mechanical Q does not have much effect. Maybe 15%. Many layers of open fabric would work best.
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Old 31st December 2008, 09:22 PM   #3
DcibeL is offline DcibeL  Canada
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Yes, the fabric basically acting as a mechanical brake, changing Qms, and Qts. I think this is something that would be hard to estimate, so measuring would be the only way to know exactly how to have changed the parameters.

If the driver is a dual voice coil, you can use only one voice coil, and use the other voice coil terminals as a magnetic brake, instead of a mechanical brake as with essentially smothering the back of the driver. A resistor can be installed across the terminals of the unused voice coil to adjust the Qts. However, using only one voice coil on a dual voice coil loudspeaker I would expect to cause a decrease in sensitivity (due to decreased BL) and power handling.
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Old 31st December 2008, 10:45 PM   #4
bjorno is offline bjorno  Sweden
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lowering Qts

This approach is very similar:

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Old 31st December 2008, 11:09 PM   #5
MCPete is offline MCPete  United States
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Default lowering Qts

Thanks to all for your replies, especially those from Earl Geddes and Bjorno.

I did search the site for pre-existing advice on this topic, but apparently not zealously enough.

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