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View Full Version : 4th order port/chamber question



Beatin'
08-14-2013, 11:38 PM
is it possible to have the front chamber also be it's own port?

Let's take a 1.66 cube chamber with the ID of 6.5in x 15.5in x 28.5in

Let's say the port opening is 6.5x15.5 and the chamber/port is 28.5 deep. winISD shows that such a chamber will be ported to about 66.25hz.

Is this possible? Does this actually work without a dedicated port? What if you put the 6.5x15.5 opening on the side of the chamber length-wise that goes to 28.5in, will the port still work?

SounDrive
08-14-2013, 11:45 PM
Doesn't sound right. You don't want a sub to be directly in front of a port, ever.

Beatin'
08-15-2013, 10:46 AM
Doesn't sound right. You don't want a sub to be directly in front of a port, ever.

The chamber IS the port. I think it's called a "clamshell".

bbeljefe
08-15-2013, 11:42 AM
As was mentioned, it isn't useful to have a speaker load directly into a port. Likewise, it isn't useful to have a port that exceeds the piston area of your driver(s). In this case, since the drivers are also loaded into Fb, there is no danger of damage but... there will also be no appreciable benefit.

That said, it will change the tuning of the cabinet but only as much as, say, repositioning the cabinet in the cabin of the vehicle.

You should refigure Fb and use a port that's about 25% of the piston area you have. Or, ~16 sq in per cubic foot of airspace.

The exception to that rule is the wave transmission line, in which the enclosure is essentially one long port that equals the Sd of the driver(s).

SounDrive
08-15-2013, 11:55 AM
As was mentioned, it isn't useful to have a speaker load directly into a port. Likewise, it isn't useful to have a port that exceeds the piston area of your driver(s). In this case, since the drivers are also loaded into Fb, there is no danger of damage but... there will also be no appreciable benefit.

That said, it will change the tuning of the cabinet but only as much as, say, repositioning the cabinet in the cabin of the vehicle.

You should refigure Fb and use a port that's about 25% of the piston area you have. Or, ~16 sq in per cubic foot of airspace.

The exception to that rule is the wave transmission line, in which the enclosure is essentially one long port that equals the Sd of the driver(s).

I've always heard to start with around half of the cone area of the drivers for port area being used when making a 4th order, but I'm not sure how accurate of a figure that is, but I believe it's what Ranger was using and he hit some pretty impressive numbers and had pretty good response, too.

---------- Post added at 10:55 AM ---------- Previous post was at 10:55 AM ----------


As was mentioned, it isn't useful to have a speaker load directly into a port. Likewise, it isn't useful to have a port that exceeds the piston area of your driver(s). In this case, since the drivers are also loaded into Fb, there is no danger of damage but... there will also be no appreciable benefit.

That said, it will change the tuning of the cabinet but only as much as, say, repositioning the cabinet in the cabin of the vehicle.

You should refigure Fb and use a port that's about 25% of the piston area you have. Or, ~16 sq in per cubic foot of airspace.

The exception to that rule is the wave transmission line, in which the enclosure is essentially one long port that equals the Sd of the driver(s).

I've always heard to start with around half of the cone area of the drivers for port area being used when making a 4th order, but I'm not sure how accurate of a figure that is, but I believe it's what Ranger was using and he hit some pretty impressive numbers and had pretty good response, too.

Buck
08-15-2013, 11:58 AM
As was mentioned, it isn't useful to have a speaker load directly into a port. Likewise, it isn't useful to have a port that exceeds the piston area of your driver(s). In this case, since the drivers are also loaded into Fb, there is no danger of damage but... there will also be no appreciable benefit.

That said, it will change the tuning of the cabinet but only as much as, say, repositioning the cabinet in the cabin of the vehicle.

You should refigure Fb and use a port that's about 25% of the piston area you have. Or, ~16 sq in per cubic foot of airspace.

The exception to that rule is the wave transmission line, in which the enclosure is essentially one long port that equals the Sd of the driver(s).

T-line's aren't exactly Sd, they can be bigger. They have to be at least Sd so no loading/pressurization occurs. For a 4th order you don't want to exceed your piston area in most cases (not even close), more like 1/2 total Sd.

Beatin'
08-15-2013, 12:05 PM
So it's better to just port the chamber properly with a 6 inch round port for example?

Buck
08-15-2013, 12:10 PM
So it's better to just port the chamber properly with a 6 inch round port for example?

Yes. With a port like that, it's sealed. That chamber does resonate according to 1/4 wave but it would be really high where it wouldn't effect the subs, it'd have to be really deep.

For a "port", you have to have separate airspace based on what you were saying because only with the combo of the air and port does the tuning work correctly.

bbeljefe
08-15-2013, 12:28 PM
Agreed, but in the interest of brevity I didn't go into a dissertation on t-lines. But actually, some driver loading is beneficial in some instances, depending on the compliance of the driver and to keep it from exceeding xmax.

T-lines are about as varied as personalities.

bbeljefe
08-15-2013, 01:02 PM
[QUOTE=Tenacious.;8453495]I've always heard to start with around half of the cone area of the drivers for port area being used when making a 4th order, but I'm not sure how accurate of a figure that is, but I believe it's what Ranger was using and he hit some pretty impressive numbers and had pretty good response, too.[COLOR="Silver"]

---------- Post added at 10:55 AM ---------- Previous post was at 10:55 AM ----------

Depends on the power and the displacement of the driver's cone.