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<blockquote data-quote="helotaxi" data-source="post: 3715021" data-attributes="member: 550915">The port works as a delay line.&nbsp; At the tuning freq, the pressure wave from the inside of the box through the port is exactly 180 deg out of phase with the motion of the driver.&nbsp; Since the port pressure is generated from the back of the sub, the net effect is that the port output is in phase with the front wave of the driver right at tuning.&nbsp; As you move away from tuning, the phase coupling becomes less exact.As far as cone control goes, the air in the port has inertia.&nbsp; As is it moves out from the port, it reduces the pressure in the box at the same time, the driver is trying to move outward as well further reducing the internal pressure of the box.&nbsp; As the air starts returning into the box from the low pressure, the driver is trying to move in, boosting the internal pressure.&nbsp; The result is that the mass of the air in the port is added to the Mms of the sub at tuning.&nbsp; Makes for much less cone movement but effectively double the cone area and thus more efficient at tuning.</blockquote>

[QUOTE="helotaxi, post: 3715021, member: 550915"] The port works as a delay line. At the tuning freq, the pressure wave from the inside of the box through the port is exactly 180 deg out of phase with the motion of the driver. Since the port pressure is generated from the back of the sub, the net effect is that the port output is in phase with the front wave of the driver right at tuning. As you move away from tuning, the phase coupling becomes less exact. As far as cone control goes, the air in the port has inertia. As is it moves out from the port, it reduces the pressure in the box at the same time, the driver is trying to move outward as well further reducing the internal pressure of the box. As the air starts returning into the box from the low pressure, the driver is trying to move in, boosting the internal pressure. The result is that the mass of the air in the port is added to the Mms of the sub at tuning. Makes for much less cone movement but effectively double the cone area and thus more efficient at tuning. [/QUOTE]

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