My current project of dual 10” sealed system floor-standing speakers is complete, my curiosity hasn’t been terminated though. I’m curious about how do these speakers sound if they are ported.
Let me describe the specifications of them. They are equipped with two identical 10” woofers. Each woofer has a closed chamber with internal volume of 47 liters (1.67 cubic foot). Box tuning frequency is 36Hz.
Here are the questions for converting them from sealed to vented system.
1. Can two woofers with total internal box volume of 2 x 47 liters = 94 liters jointly use a single port, which is firing down the floor?
2. In calculation of minimum port diameter according to this online calculator:
https://www.ajdesigner.com/phpvent/subwoofer_vent_port_equation_minimum_diameter.php,
2.1. Should the effective diameter be 10” or 15” (approximation of two woofers)?
2.2. Does the Xmax have to be twice, halve, or stay the same as original?
2.3. How much should the new tuning frequency for vented system be, with 36Hz in sealed system?
Let me describe the specifications of them. They are equipped with two identical 10” woofers. Each woofer has a closed chamber with internal volume of 47 liters (1.67 cubic foot). Box tuning frequency is 36Hz.
Here are the questions for converting them from sealed to vented system.
1. Can two woofers with total internal box volume of 2 x 47 liters = 94 liters jointly use a single port, which is firing down the floor?
2. In calculation of minimum port diameter according to this online calculator:
https://www.ajdesigner.com/phpvent/subwoofer_vent_port_equation_minimum_diameter.php,
2.1. Should the effective diameter be 10” or 15” (approximation of two woofers)?
2.2. Does the Xmax have to be twice, halve, or stay the same as original?
2.3. How much should the new tuning frequency for vented system be, with 36Hz in sealed system?
Well, an effective diameter of 10" to tune that low with such a small net volume in the cabinet, means you'll have a monstrous sized port to do this. Not practical. The tuning of the system depends on the Fs of the drivers potentially and really the cabinet itself. Tuning 28hz for example will require a huge long port due to the smaller volume of the system, unless you go with a tiny vent diameter.
So the compromise to try this is to just go with a smaller port diameter. Likely something closer to 50mm / 2" or so and accept the potential for chuffing or compression. I wouldn't really worry about the woofers for this test, without re-building this totally custom. I would just take the actual volume the port will see and adjust the port to that for your desired tuning and just see what you get. It won't be ideal or perfect, it can't be, due to the volume of the cabinet.
Very best,
So the compromise to try this is to just go with a smaller port diameter. Likely something closer to 50mm / 2" or so and accept the potential for chuffing or compression. I wouldn't really worry about the woofers for this test, without re-building this totally custom. I would just take the actual volume the port will see and adjust the port to that for your desired tuning and just see what you get. It won't be ideal or perfect, it can't be, due to the volume of the cabinet.
Very best,
So, let's say you have a 1.65 ft^3 net volume per driver. And you wanted to put a port into both of them, tuned to 25hz, to lift 28hz~30hz a bit, and not run out of excursion until down under 22hz or so.
If the port is closer to a corner/wall it will have a larger end correction factor. So if we guess around end correction 1.2, we can do a 2" diameter port that is 14~15cm long and get to 25hz. About 5 inches. Being off a little is ok, it will barely change anything by much. So you would just add a 2" diameter by 5" length port to an area near the bottom wall of each chamber.
But what if end correction was closer to 1.7? Or anything else really. It won't matter, it changed the tuning by 1hz difference. Very safe.
Very best,
If the port is closer to a corner/wall it will have a larger end correction factor. So if we guess around end correction 1.2, we can do a 2" diameter port that is 14~15cm long and get to 25hz. About 5 inches. Being off a little is ok, it will barely change anything by much. So you would just add a 2" diameter by 5" length port to an area near the bottom wall of each chamber.
But what if end correction was closer to 1.7? Or anything else really. It won't matter, it changed the tuning by 1hz difference. Very safe.
Very best,
