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Author Topic: Port Area  (Read 623 times)

Andrew Watts

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Port Area
« on: October 28, 2022, 09:08:01 PM »

I am modifying some sub boxes to house 1x18 inch driver.
The driver is a B&C 18PXB46. The cabinet is only 140 litres, but models an acceptable response tuned to 40hz. The cabs have a single 6 inch port. At 40hz, it only needs to around 4 inches long. Do you think the port would be large enough to gangle the air movement without artifacts?
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David Morison

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Re: Port Area
« Reply #1 on: October 29, 2022, 09:54:19 AM »

I am modifying some sub boxes to house 1x18 inch driver.
The driver is a B&C 18PXB46. The cabinet is only 140 litres, but models an acceptable response tuned to 40hz. The cabs have a single 6 inch port. At 40hz, it only needs to around 4 inches long. Do you think the port would be large enough to gangle the air movement without artifacts?

Probably not, no.

First though, can I check if you meant 18PZB46 please? (Easy typo to make after all, & I've never heard of a PXB, unless it's an OEM for some other company that you're re-using?)

Assuming PZB, then in 140l tuned to 40Hz you're going to have vent airspeed about 37ms-1 when driven to XVar, so I'd expect it would be worth adding a second vent, even though that does mean more surgery to the cab and a slight reduction in net cabinet volume.

HTH,
David.
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Andrew Watts

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Re: Port Area
« Reply #2 on: October 29, 2022, 06:20:24 PM »

Probably not, no.

First though, can I check if you meant 18PZB46 please? (Easy typo to make after all, & I've never heard of a PXB, unless it's an OEM for some other company that you're re-using?)

Assuming PZB, then in 140l tuned to 40Hz you're going to have vent airspeed about 37ms-1 when driven to XVar, so I'd expect it would be worth adding a second vent, even though that does mean more surgery to the cab and a slight reduction in net cabinet volume.

HTH,
David.

Sorry David. Yes a typo. Itís very tight in the cab face, so Iím not sure how Iíll go. I just tried the driver with the single port. Seems to sound good, but I havenít driven it to Xmax
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Ivan Beaver

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Re: Port Area
« Reply #3 on: November 01, 2022, 08:15:58 AM »

Sorry David. Yes a typo. Itís very tight in the cab face, so Iím not sure how Iíll go. I just tried the driver with the single port. Seems to sound good, but I havenít driven it to Xmax
Where the port area starts to matter is at higher levels of excursion.  At lower levels a smaller diameter port can work fine.

A smaller port cannot pass the larger amount of air without "chuffing" or whistling and other sounds.

It is best not to force the air through the port, and rather "let it flow".
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Andrew Watts

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Re: Port Area
« Reply #4 on: November 05, 2022, 06:25:50 AM »

Where the port area starts to matter is at higher levels of excursion.  At lower levels a smaller diameter port can work fine.

A smaller port cannot pass the larger amount of air without "chuffing" or whistling and other sounds.

It is best not to force the air through the port, and rather "let it flow".

Thank.
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ProSoundWeb Community

Re: Port Area
¬ę Reply #4 on: November 05, 2022, 06:25:50 AM ¬Ľ


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