GTPJAY

iTrader: (2)

I have 2 Pioneer TS-W256C (10" 800Wmax, 350W normal)

I am putting them into a 98 Grand Prix and I want a ported box.

The design I am going with is 2 seperate ported boxes with a 12" wide passthrough inbetween. Reason being the rear seats don't fold down in the Grand Prix but there is a fold down passthrough in the back seat which I am keeping. Sorta like this....
http://www.clubgp.com/mods/64/08%20c...in%20trunk.jpg

Anyways. I'm following the recomendations for the box sizes etc. that came with the sub and it suggests using a 3" round x 8" long port.

Rather then doing this, could I go with a rectangular port, 1.25"x10"x4.5" ?

I calculated the colume of both and they are the same.

The rectangular port would be on the front just below the sub sorta like this: http://www.pioneerelectronics.com/pi...76572UDW12.jpg
Would this be ok?

Dukk

Ports are not about volume - length increases when area increases.

You can replace your 3" diameter vent with a rectangular one of the same AREA as long as you keep the 8" LENGTH the same.

GTPJAY

iTrader: (2)

Ok, so.....

Surface area of the 3x8 round port = pi*D*8=75.4 sq in
Surface area of the rectangular port = 2(10*4.5)+2(1.25*4.5)=101.25 sq in

101.25-75.4=25.85 sq in increase, or 25.85/75.4=34.3% increase in surface area.

We therefore need a proportional decrease in length. 100%-34.3%=65.7% of the original length. 8" *65.7%=5.25". So based on these #s, rectangular port needs to be .75" longer...

So then it would be 1.25"x10"x5.25" ? Then the volume changes, does this matter?

BigRedGuy

iTrader: (11)

The link above didn't work, but I found it here: GP Box Design

Hmmm....my take on the math.....

Surface area of the 3" port is 9.42 sq in.

If the slot port is 10" long, it should be at least 2" wide to avoid port noise...allowing for the increased surface area and the use of the enclosure as 1 side of the vent, it will need to be approx. 16" long.

If the length of the vent is a problem, 4.7" X 2" vent 7" long built on the side of the box will get the job done.....

If the width is an issue, you could try 9.42" X 1" and keep it 7" long, but port noise may be a problem.

Depending on which design you use, you will need to adjust the enclosure size to compensate for the volume of the vent.

HTH

GTPJAY

iTrader: (2)

So I was thinking about a few things talking to people and it seems the specs that come with the subs are tuning it for 41Hz, which is crap. So now I think I'm going to start over.... link to specs: http://www.pioneerelectronics.com/pio/pe/images/portal/cit_11221/199784721TRD1247-A_US.pdf

I am using this calculator that I just found in the other thread (THANKS) http://www.accelerator-pedal.com/ported-box.asp

I enter this:
External Box width: 36
External Box Height: 16.25
Nominal Diameter: 10" round
Woofer xmax: 10.4mm
Driver Displacement: 0.889 cf
Number of woofers: 2
Net Volume 2.5 cu ft.
tuning frequency: 35hz

and this is what it's telling me:

Net Volume: 2.5 cubic feet
Tuning Frequency: 35 Hz
Port Width: 2 inches
Port Area: 29.5 Square Inches
Port Length: 21.5 inches

External Dimensions: 36 wide x 16.25 tall x 17.75 deep

If you go on the link and input what I did you can see the shape of the box.

It's not seperated in the middle would most people put in a dividing wall with a hole to act as bracing?

Is this better then using round ports?

hofulstrof

hey man when useing that calculator, once you have your drawing up copy the url and paste it here than we can all see it.
if you read the information porst in m other thread (where you found the calcualotr) you will seee i posted that this calculator is not perfect and will not draw in any braceing but for a box of this size my may not need any braceing


i would suggest a 2.0cf box tuned to 35hz with 25sq"of port

GTPJAY

iTrader: (2)

Just tried 2 cu ft. This would fit much better in my car. Still can't use the pass through, but if this means the subs will sound better then It's worth it.

Tuned at 35hz

http://www.accelerator-pedal.com/ported-box.asp?Ew=36&Eh=16.25&Dia=4&Xmax=10.4&Vd=0.889&Nu mW=2&Vb=2&Fb=35&Qts=&Vas=&Fs=&CE=0

Tuned at 30hz

http://www.accelerator-pedal.com/ported-box.asp?Ew=36&Eh=16.25&Dia=4&Xmax=10.4&Vd=0.889&Nu mW=2&Vb=2&Fb=30&Qts=&Vas=&Fs=&CE=0
so would I need to add bracing to a box like this? The angle in the corners?

hofulstrof

. i still suggest tuning to 35hz. yes it is always a good idea to add braceing.i would suggest adding one from where the port ends to the middle of the baffle (front pannel) and you dont have add any angeled pices but it never hurts to add them.

GTPJAY

iTrader: (2)

Ok, Thanks, I think I will be re-doing my box like this then.

Is there a rule of thumb for how big the hole should be in the bracing?

I noticed a box you made had a square hole in the middle.

hofulstrof

there is no rule of thumb. if the pannel was 12" by 12" i would cut out an 8"diameter circle.and if i was doing a sqare,i like to leave at least 3" on every side