can some one give me the port length for a sub box that measures 34*11*11*14 inches and size tube to use...
Replies (17)
Ash on 06/25/2006 10:37:01
In order to give a proper port size & length, more parameters will be needed. We wil need the subs parameters and the desired cutoff frequency (F3 hz).
What sub(s) are you using?
joeinpa1969 on 06/25/2006 11:29:52
audio bahn 12 inch AW1251se is the sub i am using and i have it in a box that measures 34 by 11top and bottom by 14 inches high wanted it as a sealed box but think i could get better as a ported box..what would you recomend?
Ash on 06/25/2006 12:46:27
Those series subs have a high Qts and generally are better suited for large sealed enclosures. Going ported with these will require very large boxes (compared to sealed) although it's output may become quite peaky.
What is the wood's thickness?
What problems or performance is it exhibiting now?
swez on 06/25/2006 12:50:19
Per Crutchfield specs:
http://www.crutchfield.com/S-l7LJnP0uJBO/cgi-bin/ProdView.asp?g=520&id=detailed_info&i=037aw1251s#Tab
Enclosure Compatibility:
Recommended Sealed Box Volume: Audiobahn recommends a sealed enclosure with an internal volume of 1.0 cu/ft to 2.0 cu/ft.
Recommended Ported Box Volume: For best response and sound quality, Audiobahn recommends a ported enclosure with an internal volume of 2.3 cu/ft with one 4" diameter x 9" long port, so that is the enclosure recommended by Crutchfield. If box space is lacking in the vehicle, Audiobahn suggests a "Space Saver" box can be used with an internal volume of 1.3 cu/ft with one 3" diameter x 6.75" long port. For high performance applications, Audiobahn's "Ultimate SPL" box design has an internal volume of 3.15 cu/ft with two 4" diameter x 12" long ports.
Swez
Ash on 06/25/2006 12:58:08
Thanks Swez! That really saved me some work.
One thing to be noted with using the different sizes for ported is the F3 and any peakiness associated with the different tunings.
joeinpa1969 on 06/25/2006 16:11:23
my box i have now for my audiobahn is 32 " long by 14 3/4 wide horizonal and 13" vertical ..Is that a good measurement for my subs..
swez on 06/25/2006 18:24:38
Depending on the thickness of wood used, that nets about 2.7 cf internally. (3/4" wood thickness and no extra braces)
Vb = internal (H x W x D) - sub/port displacement and internal braces = net Vb.
If you know the wood thickness, we can nail it down to tune your box more precisely. I used a wood thickness of 3/4" for this calculation. If the box is 5/8" or 1.0" thick MDF or has internal support braces, the internal cf airspace will vary.
For a Port Tuning Frequency (PTF) of ~ 36 Hz., your port needs to be 4.0" dia, and 6.75" long. This assumes a net Vb of ~2.7 cf.
NOTE: As Vb gets smaller, we go longer on the port tube length for the same PTF target.
Hope that helps,
Swez
joeinpa1969 on 06/25/2006 19:56:30
i used 1/2 inch plywood i plan on building one with 5/8 sometime i have some bracing in side ...
Ash on 06/25/2006 20:13:01
That I don't recommend. Being that it is a large type enclosure, you are better off using 3/4" mdf. It costs a bit more ($20-24 per full sheet), but is well worth it. Using thinner and less denser material will insure a not so solid box with a less than par sub performance.
joeinpa1969 on 06/26/2006 04:51:27
ok so for that sub box size and thickness what would the port be?
swez on 06/26/2006 09:30:08
Generic plywood usually makes for a poor subwoofer enclosure. It tends to have many voids in the laminated plys which often lead to rattles.
Use 3/4" MDF (Medium Density Fiberboard) when you make the new box. This is a pretty dense material, easy to cut and shape and no voids at all.
"Audiobahn recommends a ported enclosure with an internal volume of 2.3 cu/ft with one 4" diameter x 9" long port."
Make your next box to the following dimensions and it should perform very well: (external dimensions) No internal bracing should be needed with 3/4" MDF of the following dimensions.
Height = 15"
Depth = 12-1/4"
Width/length = 30"
The internal airspace will be 2.39 cf. When you subtract sub and port displacements, you'll be at 2.3 cf internal.
The PTF of this box will be about 35 Hz., if you go with a 4" round port and 9" long. Port you can use: (4.0" dia, cut to length and glue the end cap as noted)
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=268-352
Does your current amp have a Sub Sonic Filter? (SSF)
Swez
joeinpa1969 on 06/26/2006 18:21:57
yes it does...have (SSF) turn half way...1000 watts bridged and 500 watts stereo...runs 4 channel...not shure of the watss..
in 4 channel but that sony explode hits hard...
swez on 06/27/2006 08:53:18
What amp are you using here Joe? (Make and model # please)
Swez
joeinpa1969 on 06/29/2006 19:40:31
i am using a sony explod model XM-2165GTX
swez on 06/29/2006 20:50:46
That amp model # states it's a 2 channel amp. It says 165 watts RMS x 2 @ 4 Ohms per channel and 400 watts RMS when bridged MONO.
That sub is a 4+4 DVC . you cannot bridge this amp to MONO mode and expect it to last very long.
Best you can do, wire 1 coil to each channel and port the enclosure per earlier directions. It should be decent bass for now. But, this is not the optimal way to use this sub and amp combination.
Swez
joeinpa1969 on 06/30/2006 04:53:16
i have my amp run stereo mode and my low pass filter is on then im stable to 2 ohm.
swez on 06/30/2006 09:51:55
Yes, the amp is 2 ohms stable in stereo mode and will deliver about 200 watts RMS per channel at 2 ohms or 400 RMS bridged MONO @ 4 ohms.
Are you running 1 sub or 2 here Joe?
Swez
Replies (17)
Ash on 06/25/2006 10:37:01
In order to give a proper port size & length, more parameters will be needed. We wil need the subs parameters and the desired cutoff frequency (F3 hz).
What sub(s) are you using?
joeinpa1969 on 06/25/2006 11:29:52
audio bahn 12 inch AW1251se is the sub i am using and i have it in a box that measures 34 by 11top and bottom by 14 inches high wanted it as a sealed box but think i could get better as a ported box..what would you recomend?
Ash on 06/25/2006 12:46:27
Those series subs have a high Qts and generally are better suited for large sealed enclosures. Going ported with these will require very large boxes (compared to sealed) although it's output may become quite peaky.
What is the wood's thickness?
What problems or performance is it exhibiting now?
swez on 06/25/2006 12:50:19
Per Crutchfield specs:
http://www.crutchfield.com/S-l7LJnP0uJBO/cgi-bin/ProdView.asp?g=520&id=detailed_info&i=037aw1251s#Tab
Enclosure Compatibility:
Recommended Sealed Box Volume: Audiobahn recommends a sealed enclosure with an internal volume of 1.0 cu/ft to 2.0 cu/ft.
Recommended Ported Box Volume: For best response and sound quality, Audiobahn recommends a ported enclosure with an internal volume of 2.3 cu/ft with one 4" diameter x 9" long port, so that is the enclosure recommended by Crutchfield. If box space is lacking in the vehicle, Audiobahn suggests a "Space Saver" box can be used with an internal volume of 1.3 cu/ft with one 3" diameter x 6.75" long port. For high performance applications, Audiobahn's "Ultimate SPL" box design has an internal volume of 3.15 cu/ft with two 4" diameter x 12" long ports.
Swez
Ash on 06/25/2006 12:58:08
Thanks Swez! That really saved me some work.
One thing to be noted with using the different sizes for ported is the F3 and any peakiness associated with the different tunings.
joeinpa1969 on 06/25/2006 16:11:23
my box i have now for my audiobahn is 32 " long by 14 3/4 wide horizonal and 13" vertical ..Is that a good measurement for my subs..
swez on 06/25/2006 18:24:38
Depending on the thickness of wood used, that nets about 2.7 cf internally. (3/4" wood thickness and no extra braces)
Vb = internal (H x W x D) - sub/port displacement and internal braces = net Vb.
If you know the wood thickness, we can nail it down to tune your box more precisely. I used a wood thickness of 3/4" for this calculation. If the box is 5/8" or 1.0" thick MDF or has internal support braces, the internal cf airspace will vary.
For a Port Tuning Frequency (PTF) of ~ 36 Hz., your port needs to be 4.0" dia, and 6.75" long. This assumes a net Vb of ~2.7 cf.
NOTE: As Vb gets smaller, we go longer on the port tube length for the same PTF target.
Hope that helps,
Swez
joeinpa1969 on 06/25/2006 19:56:30
i used 1/2 inch plywood i plan on building one with 5/8 sometime i have some bracing in side ...
Ash on 06/25/2006 20:13:01
That I don't recommend. Being that it is a large type enclosure, you are better off using 3/4" mdf. It costs a bit more ($20-24 per full sheet), but is well worth it. Using thinner and less denser material will insure a not so solid box with a less than par sub performance.
joeinpa1969 on 06/26/2006 04:51:27
ok so for that sub box size and thickness what would the port be?
swez on 06/26/2006 09:30:08
Generic plywood usually makes for a poor subwoofer enclosure. It tends to have many voids in the laminated plys which often lead to rattles.
Use 3/4" MDF (Medium Density Fiberboard) when you make the new box. This is a pretty dense material, easy to cut and shape and no voids at all.
"Audiobahn recommends a ported enclosure with an internal volume of 2.3 cu/ft with one 4" diameter x 9" long port."
Make your next box to the following dimensions and it should perform very well: (external dimensions) No internal bracing should be needed with 3/4" MDF of the following dimensions.
Height = 15"
Depth = 12-1/4"
Width/length = 30"
The internal airspace will be 2.39 cf. When you subtract sub and port displacements, you'll be at 2.3 cf internal.
The PTF of this box will be about 35 Hz., if you go with a 4" round port and 9" long. Port you can use: (4.0" dia, cut to length and glue the end cap as noted)
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=268-352
Does your current amp have a Sub Sonic Filter? (SSF)
Swez
joeinpa1969 on 06/26/2006 18:21:57
yes it does...have (SSF) turn half way...1000 watts bridged and 500 watts stereo...runs 4 channel...not shure of the watss..
in 4 channel but that sony explode hits hard...
swez on 06/27/2006 08:53:18
What amp are you using here Joe? (Make and model # please)
Swez
joeinpa1969 on 06/29/2006 19:40:31
i am using a sony explod model XM-2165GTX
swez on 06/29/2006 20:50:46
That amp model # states it's a 2 channel amp. It says 165 watts RMS x 2 @ 4 Ohms per channel and 400 watts RMS when bridged MONO.
That sub is a 4+4 DVC . you cannot bridge this amp to MONO mode and expect it to last very long.
Best you can do, wire 1 coil to each channel and port the enclosure per earlier directions. It should be decent bass for now. But, this is not the optimal way to use this sub and amp combination.
Swez
joeinpa1969 on 06/30/2006 04:53:16
i have my amp run stereo mode and my low pass filter is on then im stable to 2 ohm.
swez on 06/30/2006 09:51:55
Yes, the amp is 2 ohms stable in stereo mode and will deliver about 200 watts RMS per channel at 2 ohms or 400 RMS bridged MONO @ 4 ohms.
Are you running 1 sub or 2 here Joe?
Swez
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