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Old 11th June 2005, 07:33 AM   #1
idahoxj is offline idahoxj  United States
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Location: idaho
Default help with a bandpass enclosure

Hey guys, I am building a sealed rear chamber bandpass enclosure for my jeep and when I try to figure out the port size I get a rediculously long port size. I think its becuase I am using just the front chamber volume. Should I use the total volume of the entire box?
These are all the specs.

The box
vf=3.664ft^3
vr=9.626ft^3
Qpb=0.88
Fb=28.51
gain=2.39
F(l)=17
s factor= 0.6
I am planning on the box being roughly 45"x17"x32"

The speakers
Qts=.72
Vas=4.908
Fs=23.2
Qes=.84
SPL=85

Thanks in Advance.
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Old 11th June 2005, 07:45 AM   #2
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what was the diameter of the port you wanted? If you go to a smaller diameter the port will get shorter. But as the port gets narrower the air speed picks up, supposedly when this gets to high you can hear the air move. I have built speakers with a resulting air speed that should be audible, but by that time the music is so loud I can't hear it. I realize this dosen't answer your box volume question but it may come in handy if your numbers are good.
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Old 11th June 2005, 05:28 PM   #3
idahoxj is offline idahoxj  United States
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I was getting a port diameter of 9.55 inches when I crunched the numbers.
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Old 27th June 2005, 03:17 AM   #4
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mabye u could use a slot or a sqaure port so that u can have a port almost as tall as the box. u might consider a smaller port diameteer like 3-4 mabye or even multi ports
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Old 5th July 2005, 08:56 AM   #5
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You're trying to tune it way to low. Tune it around 50hz or higher ... unless you want your in-car response to "peak" at about 20Hz and not play much of anything above 30.

if the vas is in ft^3 then I should one sub looking nice in ~1.5ft^3 rear and 2.9ft^3 front tuned to 48Hz via 6"x6"x8.375" D port ... might play a little low for most people tho ... passband of ~40Hz ... 30Hz to 70Hz
in-car should be pretty mean from mid 30's to mid 50's with a gradual slope above 50 ...
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