Hi Chris, if you calculate 1/4 wavelegth, the actual tuning frequence will be lower than expected due to the mass of the air in the opening. Martin J. King explains this very well on his site.
For a driver with high or moderate high Qts (0.40) tuning of the cabinet can be 5-10 Hz lower than the Fs of the driver. For low Qts drivers, tuning should be set higher than driver Fs. This is a general rule of thumb, however.
Tuning of the cabinet depends on geometry. For a given length, a tapered cabinet will have a lower tuning frequency than a straight line. A mass loaded (with a vent) is doing the same thing.
For your information, see the picture enclosed of my quarter wave for the 3" Tang Band (I named it TABAQ) the mass loading is a small "vent" at the bottom. This type geometry is very easy to build, and of course, you can fold it. The opening is 0.5 Sd, by the way.
Hi from Bjorn
For a driver with high or moderate high Qts (0.40) tuning of the cabinet can be 5-10 Hz lower than the Fs of the driver. For low Qts drivers, tuning should be set higher than driver Fs. This is a general rule of thumb, however.
Tuning of the cabinet depends on geometry. For a given length, a tapered cabinet will have a lower tuning frequency than a straight line. A mass loaded (with a vent) is doing the same thing.
For your information, see the picture enclosed of my quarter wave for the 3" Tang Band (I named it TABAQ) the mass loading is a small "vent" at the bottom. This type geometry is very easy to build, and of course, you can fold it. The opening is 0.5 Sd, by the way.
Hi from Bjorn
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