Port direction in relation to woofer direction

[[email protected]]

I am trying to design an enclosure that will fit in the back of my
vehicle, and it seems I am left with only one option that will
accomodate box volume, port length, and basket depth. The issue I am
having with this design is that the port will exit the enclosure in a
way that the front and rear sound from the subwoofer cross eachother at
90 degrees from eachother. (the port is in front of the outward facing
side of the sub, at a right angle to the sub.)

What issues, if any, will i have with phase/cancellation?

[KU40]

shouldn't have any. waves need to be at 180 degrees from each other to
cancel out, so 90 won't do it. this type of configuration works the
best in some vehicles, SPLers found out sub up, port back in those
little honda CRXs works the best.


--
KU40

[GregS]

In article >, KU40 > wrote:
>
>shouldn't have any. waves need to be at 180 degrees from each other to
>cancel out, so 90 won't do it. this type of configuration works the
>best in some vehicles, SPLers found out sub up, port back in those
>little honda CRXs works the best.

Below the freuency of the port, so to speak, most all of the sound is comming from the port.
Having the port near the back reinforces the overall bass. Above the port frequency, the actuall woofer starts
to speak. In between, thats where the woofer and port compete. In close quarters, as in a car, positions
of ports and persons, probably still will not matter much. There might be more to this??

greg

[[email protected]]

GregS wrote:
> In article >, KU40 > wrote:
> >
> >shouldn't have any. waves need to be at 180 degrees from each other to
> >cancel out, so 90 won't do it. this type of configuration works the
> >best in some vehicles, SPLers found out sub up, port back in those
> >little honda CRXs works the best.
>
> Below the freuency of the port, so to speak, most all of the sound is comming from the port.
> Having the port near the back reinforces the overall bass. Above the port frequency, the actuall woofer starts
> to speak. In between, thats where the woofer and port compete. In close quarters, as in a car, positions
> of ports and persons, probably still will not matter much. There might be more to this??
>
> greg


really my only concern is that the waves will actually end up
intersecting directly in front of the subwoofer. the port would be
facing upwards from the floor, while the sub would be facing toward the
back of the car. I've had plenty of enclosures with port/driver on
different surfaces, but never where the waves would intersect as they
would in this configuration.....

[almond]

shouldn't be a problem, alot of boxes have the ports on the sides. mine
has it on the back corner and the sub in the front. i don't have any
problems at all.


--
almond

[keith]

Well, it's been a while, but AFAIK the wave lengths are 8-12ft (please
double check that info), so it comes down to measuring from port to
intersection point (including reflective surfaces), and comparing that
to the wave lengths for the frequencies you are interested in.

I hate to link to the same article twice in a week, but this one
addresses this issue somewhat.
http://installer.com/tech/aiming.html

Hope that helps

KeithS

wrote:
> I am trying to design an enclosure that will fit in the back of my
> vehicle, and it seems I am left with only one option that will
> accomodate box volume, port length, and basket depth. The issue I am
> having with this design is that the port will exit the enclosure in a
> way that the front and rear sound from the subwoofer cross eachother at
> 90 degrees from eachother. (the port is in front of the outward facing
> side of the sub, at a right angle to the sub.)
>
> What issues, if any, will i have with phase/cancellation?
>

[MOSFET]

> shouldn't be a problem, alot of boxes have the ports on the sides. mine
> has it on the back corner and the sub in the front. i don't have any
> problems at all.
>
>
> --
> almond

I agree. I once built a sub with the woofer facing the back and the port
facing up (at 90 degrees) so the bass would come up through holes in the
rear deck. This worked GREAT!! I was not aware of any cancellation issues
at all.

MOSFET

[[email protected]]

MOSFET wrote:
> > shouldn't be a problem, alot of boxes have the ports on the sides. mine
> > has it on the back corner and the sub in the front. i don't have any
> > problems at all.
> >
> >
> > --
> > almond
>
> I agree. I once built a sub with the woofer facing the back and the port
> facing up (at 90 degrees) so the bass would come up through holes in the
> rear deck. This worked GREAT!! I was not aware of any cancellation issues
> at all.
>
> MOSFET

just want to make sure you realize what i mean..... imagine a box in a
trunk, sub facing backwards, with about 12 inches between the sub and
the trunk lid. now imagine the port coming OUT OF THE FLOOR between the
box and the trunk lid. this is basically the concept of the enclosure i
am thinking of building.. the sound waves cross almost IMMEDIATELY
after exiting the enclosure..

[KU40]

so the opening of the port is on the top side of the box, right? that's
fine.


--
KU40

[[email protected]]

KU40 wrote:
> so the opening of the port is on the top side of the box, right? that's
> fine.
>
>
> --
> KU40

the port is on the bottom, firing upward. I guess the best way do
describe it would be saying the box is "L" shaped, with the sub on the
vertical portion of the "L" and the port on the horizontal portion of
the "L" and in a way that they are both firing out of the "inside part"
of the "L" so their paths cross. I'm not sure if I am explaining this
correctly. I really don't think the setup will cause problems, but I'm
having trouble getting a definitive answer from ANYONE whether there
would be any issues. Even the tech center for the subwoofer
manufacturer was stumped. They said they've never tried that type of
setup before and couldn't even predict the outcome.

[KU40]

shouldn't be a problem. it's really no different than having port and
sub on two adjacent sides in a regular rectangle box. the waves will
bounce off the wall they are firing into and eventually run into each
other in the exact same fashion as your box will, just a fraction of a
second later.


--
KU40