I need a quick bit of help. Tommarow I am going to start building a ported box for a pair of Alpine 12" Type-E subwoofers. They recomend 1.25-2.0 ft^3 airspace, so, I figure that a wedge box 15H x 34W x 19 Dbottom / 15 Dtop should work. I plan on putting 4" PCV ports through the top of the box, ported through the rear deck. Heres the dillemas. First should I use a common enclosure or put in a divider? Second, tuned at approx 29-34Hz, how do I figure out port lengths?? I tried using the WinISD program, but it gave me something like 35" ports!!! Any suggestions to my ideas would be helpful!!
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Help from the audio gurus!!
- Thread starter WackyWRZ
- Start date
RE: Help from the audio gurus!!
You'll have to use ports smaller than 4" to get a shorter length.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
You'll have to use ports smaller than 4" to get a shorter length.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
RE: Help from the audio gurus!!
[div class="dcquote"][strong]Quote[/strong]
With smaller ports, I'll want more in quantity to prevent noise though, correct?
[/div]It's true that you want the largest ports you can to reduce velocity noise, but the problem is that as port area goes up so does port length required for a given resonant frequency. It's all a trade off...
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
[div class="dcquote"][strong]Quote[/strong]
With smaller ports, I'll want more in quantity to prevent noise though, correct?
[/div]It's true that you want the largest ports you can to reduce velocity noise, but the problem is that as port area goes up so does port length required for a given resonant frequency. It's all a trade off...
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
RE: Help from the audio gurus!!
Ok, I think I'm getting it now. I did some playing with numbers, and it seems that if I make a common enclosure for both, w/o divider, that I can make 2x15.xx" ports, that I can extend out of the box slightly, and that should work fine, and change to a 30HZ tuning freq.
Ok, I think I'm getting it now. I did some playing with numbers, and it seems that if I make a common enclosure for both, w/o divider, that I can make 2x15.xx" ports, that I can extend out of the box slightly, and that should work fine, and change to a 30HZ tuning freq.
RE: Help from the audio gurus!!
Let me know the internal volume you've calculated and I'll run some numbers myself. It'd especially be helpful if you have a link to the T/S parameters for the speakers, though I could still calculate the ports based on tuning frequency of the cabinet alone.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
Let me know the internal volume you've calculated and I'll run some numbers myself. It'd especially be helpful if you have a link to the T/S parameters for the speakers, though I could still calculate the ports based on tuning frequency of the cabinet alone.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
RE: Help from the audio gurus!!
http://members.cox.net/wackywrz/sub.pdf is the parameters for the sub (SWE-1241). I have came up with 4.55 cubic ft. total for the 2. If you think a bigger/smaller box would be better, just let me know, so I can modify the size. THANKS!!!
I used to just build a box that fit my space, and throw in a 4"PVC pipe I had laying around, but after spending hours building a box, and having it sound like $hit, I am trying to really make a good one here.
http://members.cox.net/wackywrz/sub.pdf is the parameters for the sub (SWE-1241). I have came up with 4.55 cubic ft. total for the 2. If you think a bigger/smaller box would be better, just let me know, so I can modify the size. THANKS!!!
I used to just build a box that fit my space, and throw in a 4"PVC pipe I had laying around, but after spending hours building a box, and having it sound like $hit, I am trying to really make a good one here.
RE: Help from the audio gurus!!
Well, at 4.55 cu.ft. internal volume and 2 speakers, I get the flatest response with those speakers by tuning the box to 25hz. Two 3" dia. ducts 9-1/2" long gives this. What dia. ports were you using for the 15.xx length? Two 4" ports 15.15" long gives me a tuned frequency of 27hz. Either way should be fine, though the 4" ducts would make for a little less vent noise, but 3" might be easier to fit. Both yield a curve with about a 3db rise around 50hz, with flat response above and below that, to about 35hz, and about -3db at 30hz. The only way to get flatter response with those speakers is with a bigger box, but it should still sound really good with what you're planning.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L
Well, at 4.55 cu.ft. internal volume and 2 speakers, I get the flatest response with those speakers by tuning the box to 25hz. Two 3" dia. ducts 9-1/2" long gives this. What dia. ports were you using for the 15.xx length? Two 4" ports 15.15" long gives me a tuned frequency of 27hz. Either way should be fine, though the 4" ducts would make for a little less vent noise, but 3" might be easier to fit. Both yield a curve with about a 3db rise around 50hz, with flat response above and below that, to about 35hz, and about -3db at 30hz. The only way to get flatter response with those speakers is with a bigger box, but it should still sound really good with what you're planning.
John
[link:www.goldengatemark8.com|Golden Gate Mark VIII Website]
http://mark8.org/users/johnaec/Mark_VIII_s.jpg
'97 Mark VIII LSC
'96 T-Bird 4.6L