simple question for 18"q

[perfecxion 0]

how much port area should use for a 6cube box with pvc ports?

is 4 4" ports enough?

[christobear 0]

12-16 sq inches of port per net cube is the rule i believe.....so you need 72-96 inches.

4 4" ports will give you ~50

i think you're gonna ned more like 6 of those

[perfecxion 0]

12-16 sq inches of port per net cube is the rule i believe.....so you need 72-96 inches.

4 4" ports will give you ~50

i think you're gonna ned more like 6 of those

i believe you are mistaken sir.

round ports are not treated the same as slot ports

Edited January 9, 2009 by perfecxion

[christobear 0]

ah, well. ill be waiting for someone to chime in too

[perfecxion 0]

this is what ive got in mind

[NB50 206]

Are these flared ports or just straight 4" ports.

[perfecxion 0]

Are these flared ports or just straight 4" ports.

just straight pvc

id add more port area if i could, but this box is really pushing my max dimensions

Edited January 9, 2009 by perfecxion

[jbob 0]

12-16 sq inches of port per net cube is the rule i believe.....so you need 72-96 inches.

4 4" ports will give you ~50

i think you're gonna ned more like 6 of those

i believe you are mistaken sir.

round ports are not treated the same as slot ports

Actually they are, you are only worrying about the area. length is how you will get your tune (and being flared, straight, or a slot will affect the necessary length)

[KU40 173]

If you make them flared it will probably be ok.

[perfecxion 0]

If you make them flared it will probably be ok.

so what i have now will not work?

flared ports are too fuggin expensive.

[NB50 206]

Do you have a router that you can use a round over bit on?

[perfecxion 0]

i might. why?

[NB50 206]

I think the ports will be fine the way they are but you could also cut the port exit hole to the inner diameter of the port and use a round over bit on it to create a cheap flare for the port then mount the ports to the back of it with a small board with a cutout of the external diameter. Kinda hard to explain but if you need more let me know.

[perfecxion 0]

i know what you mean, but if was going to do that much work, then id just do this:

http://www.subwoofer-builder.com/flares-25mm.htm

Edited January 9, 2009 by perfecxion

[NB50 206]

pfft

What the hell is stopping you then?

O and I got a new bookmark. Thanks

[Adrian_D 520]

12-16 sq inches of port per net cube is the rule i believe.....so you need 72-96 inches.

4 4" ports will give you ~50

i think you're gonna ned more like 6 of those

i believe you are mistaken sir.

round ports are not treated the same as slot ports

Surface is surface ? I know some turbulences can appear in a slot port compared to a round port, not sure if it's a very large concern in the case of a setup which plays music all day long. Shine the light please

DIY flared ports are a nice idea too.

[95Honda 486]

The flares help, but not as much as everyone makes them out too.... If you need a 4" (non-flared) port, and you decide to go with a flared port, you are better off still using a 4" flare port..

And the vent area is NOT determained by box volume. Ever.

It is determained by the displacement of the driver. The more air you displace, the more port surface area you need. If you run that 18 with roughly half the power, only 2 ports would be fine. If you ran it with roughly a quarter of the power, 1 would be fine.

The only way to answer your question is to model the driver in that box with your predicted power and look at the vent velocity, if it is low enough, you'll be fine...

And the quick answer, 4 x 4" ports are fine for almost any 18" driver under most circumstances....

[perfecxion 0]

The flares help, but not as much as everyone makes them out too.... If you need a 4" (non-flared) port, and you decide to go with a flared port, you are better off still using a 4" flare port..

And the vent area is NOT determained by box volume. Ever.

It is determained by the displacement of the driver. The more air you displace, the more port surface area you need. If you run that 18 with roughly half the power, only 2 ports would be fine. If you ran it with roughly a quarter of the power, 1 would be fine.

The only way to answer your question is to model the driver in that box with your predicted power and look at the vent velocity, if it is low enough, you'll be fine...

And the quick answer, 4 x 4" ports are fine for almost any 18" driver under most circumstances....

Thank you!