As my other topic states, I am going to build a cabinet for my friends 2008 Astra 3 door, and I wanted to experiment with a dual chamber ported enclosure (eg. http://www.diysubwoofers.org/prt/dual_chamber.htm). From what I understand is that it will increase power handling a little to due to reduced excursion in this box, but it will also put out a little bit more bass. I have also heard that you lose a few dB between 100-120Hz.
Have any of you guys built a dual chamber ported box and can add some input to help my decision?
Replies (11)
ttocs on 12/20/2008 10:35:56
this box is also refered to as a band-pass box because of the way it works. IT will give added bass over a small band of frequencies(band-pass) but will also give reduced output over a large range of frequencies before and after the center freq.
Ash on 12/20/2008 10:59:31
Unless you have prior experience with intricate box building, I wouldn't suggest that you go with that design. It's very easy to get it wrong and even if it's built right it has to match the car's acoustics to have a good response. This is what has gained bandpass boxes notoriety...
I've noticed that you have posted before on your friend's ride. Do you know exactly what he wants and is willing to spend to get it? There are some add-on bass modules that will suffice and require less guesswork & possibly money like an Infinity Basslink.
http://www.sonicelectronix.com/item_372_Infinity+BassLink.html
cplkittle on 12/20/2008 14:11:20
If you want to give it a shot, I have had good luck with a 1:2 ratio sealed to ported. On a 10 or 12, try a 1.5 cu ft : 3 cu ft box. This will be big, but you have to keep a ratio with the ported side being larger. On top of that - the larger the sealed side the more the sub moves at lower frequencies.
I built 3 before I finally had something to experiment with. My 5th one made me proud. It takes a lot of time and a lot of wood, and takes up alot of space in the vehicle.
newB on 12/21/2008 00:55:45
i've dabbled GRIN
**ports moved due to cancellation
-Drew
cplkittle on 12/21/2008 01:09:48
did that ever work for you Drew?
newB on 12/21/2008 14:26:04
yeah it did- but i had a serious loss in output in the middle frequencies. I played around with it for fun but never had the time to edit/refine so it was rough. CrAzY lows and good high bass but there was just something missing where they met (improved after moving ports but still not fully satisfied)
-Drew
cplkittle on 12/21/2008 23:28:08
I miss the anticipation of listening to a box for the first time. Hours of planning, hours of building all comes down to one moment.. the moment of truth. I always chose a really slow sweep something that started at 200Hz and stopped at around 10Hz.
I was either really proud or really aggravated. Luckily I only had a few that really flopped. one 6th order and my first two transmission lines..
Victor on 12/22/2008 01:13:48
Never built one, not even for trying as i never found it worth sacrificing really important pass band for some low freq extension...
these do very well low freq re-reinforcement in home theater applications rather than car audio...
Ash on 12/23/2008 07:19:47
I've built quite a few bandpass' in my earlier experimental days. All 4th order though which is the simplest. Even still they are a highly "hit or miss" project without proper acoustics to match their output. At the same time when compared to a simple vented design there is no great advantage to one unless you are shooting for extra output & efficiency in a certain range. You almost have to have an RTA to properly build one for a specific vehicle so it will produce the sound you want. On paper it may look good, but it may turn out to be far from what was desired.
I still like to dabble every now & then, but only with small drivers so it will have an inherent advantage in size, output, and efficiency. I won't cross them off as unusable, but it's rare when one could be of real use.
hooviemoto87 on 01/2/2009 14:56:26
Getting back to this a bit late, but thanks for the input. I was on vacation in PA.
NEWB has a good point. Usually in the 80-100hz range you loose some bass with a dual ported system. Unless you do a lot of heavy bass stuff, then your audiophile ear might be hurting. You did a great job on that box though. Thanks a lot for those pics and advice.
ASH - I do have a lot of experience, so the calculations and building isn't a problem! :)...I've built some folded horns and other horn loaded equipment before...those are fun...
swez on 01/2/2009 23:40:15
Folded horn enclosures are great for large venue, big HT rooms and outdoor applications. They tend to push low bass waves deep into the listening area, but for accuracy and punch in a car, Nope! (Mid-long throw bass only)
For a daily driver sealed is well balanced and has a nice roll-off curve for most music. If Rap and Hip-Hop SPL is the target, use a larger ported design. The PTF target here might be closer to 32 Hz.
Swez
Have any of you guys built a dual chamber ported box and can add some input to help my decision?
Replies (11)
ttocs on 12/20/2008 10:35:56
this box is also refered to as a band-pass box because of the way it works. IT will give added bass over a small band of frequencies(band-pass) but will also give reduced output over a large range of frequencies before and after the center freq.
Ash on 12/20/2008 10:59:31
Unless you have prior experience with intricate box building, I wouldn't suggest that you go with that design. It's very easy to get it wrong and even if it's built right it has to match the car's acoustics to have a good response. This is what has gained bandpass boxes notoriety...
I've noticed that you have posted before on your friend's ride. Do you know exactly what he wants and is willing to spend to get it? There are some add-on bass modules that will suffice and require less guesswork & possibly money like an Infinity Basslink.
http://www.sonicelectronix.com/item_372_Infinity+BassLink.html
cplkittle on 12/20/2008 14:11:20
If you want to give it a shot, I have had good luck with a 1:2 ratio sealed to ported. On a 10 or 12, try a 1.5 cu ft : 3 cu ft box. This will be big, but you have to keep a ratio with the ported side being larger. On top of that - the larger the sealed side the more the sub moves at lower frequencies.
I built 3 before I finally had something to experiment with. My 5th one made me proud. It takes a lot of time and a lot of wood, and takes up alot of space in the vehicle.
newB on 12/21/2008 00:55:45
i've dabbled GRIN
**ports moved due to cancellation
-Drew
cplkittle on 12/21/2008 01:09:48
did that ever work for you Drew?
newB on 12/21/2008 14:26:04
yeah it did- but i had a serious loss in output in the middle frequencies. I played around with it for fun but never had the time to edit/refine so it was rough. CrAzY lows and good high bass but there was just something missing where they met (improved after moving ports but still not fully satisfied)
-Drew
cplkittle on 12/21/2008 23:28:08
I miss the anticipation of listening to a box for the first time. Hours of planning, hours of building all comes down to one moment.. the moment of truth. I always chose a really slow sweep something that started at 200Hz and stopped at around 10Hz.
I was either really proud or really aggravated. Luckily I only had a few that really flopped. one 6th order and my first two transmission lines..
Victor on 12/22/2008 01:13:48
Never built one, not even for trying as i never found it worth sacrificing really important pass band for some low freq extension...
these do very well low freq re-reinforcement in home theater applications rather than car audio...
Ash on 12/23/2008 07:19:47
I've built quite a few bandpass' in my earlier experimental days. All 4th order though which is the simplest. Even still they are a highly "hit or miss" project without proper acoustics to match their output. At the same time when compared to a simple vented design there is no great advantage to one unless you are shooting for extra output & efficiency in a certain range. You almost have to have an RTA to properly build one for a specific vehicle so it will produce the sound you want. On paper it may look good, but it may turn out to be far from what was desired.
I still like to dabble every now & then, but only with small drivers so it will have an inherent advantage in size, output, and efficiency. I won't cross them off as unusable, but it's rare when one could be of real use.
hooviemoto87 on 01/2/2009 14:56:26
Getting back to this a bit late, but thanks for the input. I was on vacation in PA.
NEWB has a good point. Usually in the 80-100hz range you loose some bass with a dual ported system. Unless you do a lot of heavy bass stuff, then your audiophile ear might be hurting. You did a great job on that box though. Thanks a lot for those pics and advice.
ASH - I do have a lot of experience, so the calculations and building isn't a problem! :)...I've built some folded horns and other horn loaded equipment before...those are fun...
swez on 01/2/2009 23:40:15
Folded horn enclosures are great for large venue, big HT rooms and outdoor applications. They tend to push low bass waves deep into the listening area, but for accuracy and punch in a car, Nope! (Mid-long throw bass only)
For a daily driver sealed is well balanced and has a nice roll-off curve for most music. If Rap and Hip-Hop SPL is the target, use a larger ported design. The PTF target here might be closer to 32 Hz.
Swez
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