I've got ports.... need everything else.

[Sheep]

Hey,

In my recent search to upgrade my subwoofer I've found that...

1.) Canada is still expensive
2.) Not a whole lot to choose from

Considering that, I have had 2 ports from a planned subwoofer build from long ago sitting in my garage. Original subwoofer was based using the Kappa Perfect, but since those are long discontinued, I am thinking I am better off starting over.

The ports I have are made by Precision, 2 inches wide, 12 inches long. I have WinISD installed, but wouldn't know where to start looking in order to find a driver/box configuration that would play well with these ports.

If anyone could lend some help it would be greatly appreciated.

SheepStar

 

[Alex2507]

Hey,

In my recent search to upgrade my subwoofer I've found that...

1.) Canada is still expensive
2.) Not a whole lot to choose from

Considering that, I have had 2 ports from a planned subwoofer build from long ago sitting in my garage. Original subwoofer was based using the Kappa Perfect, but since those are long discontinued, I am thinking I am better off starting over.

The ports I have are made by Precision, 2 inches wide, 12 inches long. I have WinISD installed, but wouldn't know where to start looking in order to find a driver/box configuration that would play well with these ports.

If anyone could lend some help it would be greatly appreciated.

SheepStar

I think Andrew's box would work with a JL Audio sub but I bet those are super expensive up there.

 

[Swerd]

The Precision ports have wide flares, but for a subwoofer a 2" diameter port might be small, leading to audible port noise, chuffing. A wider diameter or several ports is the usual solution.

You have to go through the Thiele/Small parameter exercise (or get someone else to do it for you) and get a box volume and port dimensions for a given driver. Then estimate the speed of the air moving through the port at 1 volt, 10 volts, 100 volts, until you arrive at Xmax. As long as the air moving through the port is 5% the speed of sound, or less, you shouldn't hear port noise.

 

[Sheep]

The Precision ports have wide flares, but for a subwoofer a 2" diameter port might be small, leading to audible port noise, chuffing. A wider diameter or several ports is the usual solution.

You have to go through the Thiele/Small parameter exercise (or get someone else to do it for you) and get a box volume and port dimensions for a given driver. Then estimate the speed of the air moving through the port at 1 volt, 10 volts, 100 volts, until you arrive at Xmax. As long as the air moving through the port is 5% the speed of sound, or less, you shouldn't hear port noise.

I have 2 of these ports... so I'm hoping it's enough. But it all boils down to the driver. I built up a box using these ports for a TC Epic 12 but it's not showing me the air speed.

 

[Swerd]

I have 2 of these ports... so I'm hoping it's enough. But it all boils down to the driver. I built up a box using these ports for a TC Epic 12 but it's not showing me the air speed.

I hope someone around here knows how to estimate port airspeed at driver Xmax. The only way I've seen is with the software Martin J King made for designing various transmission line cabinets. There's an example in the 2nd post in the DIY ER18 MTM thread started by skyline_123:

At this same elevated input, the port’s air velocity should be just over 3% the speed of sound, and the system should generate about 103 dB. With a rear mounted port, there should be no audible port noise:

What was the tuning of the ports for your cabinet with the TC 12 driver?

Often people don't have a predicted port airspeed and they play it safe by using a larger diameter port. But then to get the same port tuning, you need a longer port tube.

Another way, but more expensive, uses passive drivers instead of ports.

 

[annunaki]

Your vents are too small. Dual 2" vents are slightly more than a single 4" Vent. An Epic 12" will need more than that to operate ideally in a vented application.

 

[Sheep]

Your vents are too small. Dual 2" vents are slightly more than a single 4" Vent. An Epic 12" will need more than that to operate ideally in a vented application.


Thanks

Yeah I was missing the Pe for the Theil small. Once added, it was .36 mach, far too much air speed.

Who knows. I know someone with a Kappa Perfect. I might try to buy it off him.

I also have cheap access to a MTX Thunder 9500 15 inch. Is this decent for a subwoofer or is it typical MTX garbage?

SheepStar