4th order bandpass box. Yes or no?

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Bug420247

CarAudio.com Newbie
So I have 2 x 12D1 Rockville Destroyers. And I was contemplating on putting them in a 4th order bandpass enclosure tuned to 30hz. I want the entire enclosure to be close to 7 ft3. I have the dimensions I want… but every time I try to use box design. Software. They never have the specific box type or the subs wired the way I do… so I cannot get an accurate tune. Does anyone have any suggestions?

So here are some of the issues:
1- Not enough T/S parameters listed on the Rockville site to plug into the software. Or the parameters listed are not what the software is asking for.
2- The software does not have an option for the way I am wiring my drivers. (Which is series-parallel)
3- Not getting port velocity feedback, x max feedback, or spl feedback on WinISD
 
I had no problem modeling those up myself. However with the ebp of those subs a vented or 6th would be a better bet imo. Since a 6th is even more involved I'd stick with ported. Op... why tune a 4th to 30hz anyways?
I do lots of 4th designs and never tune them under 40hz, usually around 45-47hz is where you want to be.
 
You can overcome the wiring thing by using a different ohm value that will spit out the correct final value.
Thank for the advice. I have to wire the way it is in order to have 1ohm at the amp. So here’s what I really after I need to know my port size will be for a rectangle port. As well as the depth of the port. On speaker box with these dimensions:
length 41.5 in.
Bottom width 17 in.
Top width 14 in.
Height 20 in.

Here are all the specs that I have for the driver. And I have two of them.
  • Cutout Diameter: 11.65” inches​
  • Mounting Depth: 8.66” inches​
  • 25mm T-Yoke + 15mm Washer​
  • Vented/Ported Enclosure Volume: 2.12-2.83 Cubic Feet​
  • Frequency response: 37 Hz - 1K kHz​
  • Sensitivity: 85.9 dB​
  • XMAX: 30 MM​
  • Re​
    1.7 Ohm​
    Electrical voice coil resistance at DC​
    Fo​
    37.649 Hz​
    Drive resonance frequency​
    Mechanical Parameters (Using Laser)
    Mms​
    244.251 g​
    Mechanical mass of drive diaphragm assembly including air load and voice coil​
    Mmd (Sd)​
    238.365g​
    Mechanical mass of voice coil and diaphragm without air load​
    Cms​
    73.163 mm/N​
    Mechanical compliance of drive suspension​
    Bl​
    14.252 N/A​
    Force factor (Bl product)​
    Loss Factors
    Qms​
    3.627​
    Mechanical Q-factor of of drive in free air considering Rms only​
    Qes​
    0.414​
    Electrical Q-factor of drive in free air considering Re only​
    Qts​
    0.357​
    Total Q-factor considering Re and Rms only​
    Other Parameters
    Vas​
    23.090​
    Equivalent air volume of suspension​
    n0​
    0.246%​
    Reference efficiency (2 pi-radiation using Re)​
    Sd​
    47.144 cm²​
    Diaphragm area​
    SPL​
    85.9dB​
    sensitivity​


    Detailed Info:

  • Gap Plate Inside Diameter: 85.5mm (3.37 inches)
  • Gap Plate Outside Diameter: 210mm (8.27 inches)
  • Gap Plate Thickness: 15mm (0.59 inch)
  • Yoke Outside Diameter:210mm (8.27 inches)Yoke Thickness: 25mm (0.98 inches)
  • Yoke Pole Diameter: 73.9mm (2.91 inches)
 
I had no problem modeling those up myself. However with the ebp of those subs a vented or 6th would be a better bet imo. Since a 6th is even more involved I'd stick with ported. Op... why tune a 4th to 30hz anyways?
I do lots of 4th designs and never tune them under 40hz, usually around 45-47hz is where you want to be.
And I was contemplating going with the four or six. If you think six would be better I can try that and the reason for the tuning is because I listen to a lot of the EDM and a lot of those frequencies are in that range
 
And I was contemplating going with the four or six. If you think six would be better I can try that and the reason for the tuning is because I listen to a lot of the EDM and a lot of those frequencies are in that range
I already have them inside of a kicker box that is ported and tuned 34 Hz, but it’s not giving me what I need
 
And I was contemplating going with the four or six. If you think six would be better I can try that and the reason for the tuning is because I listen to a lot of the EDM and a lot of those frequencies are in that range
A mid 40's tuned 4th will dig just fine and deliver what you want. It seems you misunderstand or are thinking a 4th is tuned like a ported box... its not. If you don't understand 4th tuning a 6th would be a nightmare.

A ported kicker box is usually tuned higher so building a properly designed enclosure in the low 30's would definitely be an improvement over what you got currently. I'd stick /w/ ported and grab a legit design then build it.

Something tells me that will be what you're after.
 
A mid 40's tuned 4th will dig just fine and deliver what you want. It seems you misunderstand or are thinking a 4th is tuned like a ported box... its not. If you don't understand 4th tuning a 6th would be a nightmare.

A ported kicker box is usually tuned higher so building a properly designed enclosure in the low 30's would definitely be an improvement over what you got currently. I'd stick /w/ ported and grab a legit design then build it.

Something tells me that will be what you're after.
It’s my understanding on the fourth order tuning, each section has its own tuning, and then the final tune, which is the Port tune… is that not correct?
 
It’s my understanding on the fourth order tuning, each section has its own tuning, and then the final tune, which is the Port tune… is that not correct?
A 4th order bandpass is mainly a sealed box. The sealed chamber will have a certain peak resonance based on the sub’s parameters and the size of the box. The ported section is almost always used to boost the peak Fc of sealed or to boost higher frequencies. The sealed side is your low tuned side in a 4th BP. The front ported chamber on a 4th works way differently than a regular ported box would. For example, with the sealed being the low tuned side, I’ve done a 4th tuned to 43 hz and the whole bass system peaked at 28-29 hz due to the low frequency of the rear chamber. The front chamber on a 4th is simply a booster chamber for the rear, and it’s usually tuned at Fc of sealed or higher, because putting any enclosure as a rear and having a front chamber with port will make the rear chamber tuned lower, due to the rear sound having to pass through a longer pathway to exit the box vs a regular sealed box or regular ported (vs a series 6th BP). Many people for daily with 4th’s tune the front to 45-50 hz. The main thing is to make sure your subs play low enough in sealed not to get choked out on the lows, because that can happen regardless of where the front chamber tuning is at.
 
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A well designed 4th is 1st off done with mid-low ebp drivers. Its a sealed rear section and vented front chamber. Then its a matter of sizing the port, while utilizing ratio to find that response your after.

8tGURq.jpg
 
It’s my understanding on the fourth order tuning, each section has its own tuning, and then the final tune, which is the Port tune… is that not correct?
OK, so if I did stick with just a ported box. With these dimensions:
length 41 1/2 in
bottom width 17 in
Top width 14 in
Height 20 in

What would my rectangular port size be as well as the port depth?
And still keep the 30 Hz tune?
 
A well designed 4th is 1st off done with mid-low ebp drivers. Its a sealed rear section and vented front chamber. Then its a matter of sizing the port, while utilizing ratio to find that response your after.

8tGURq.jpg
Damn! None of the research that I have done has shown anything like that. That’s for six speakers… no? And the Rockville’s are designed for SPL. Which is truly what I want. I want loud and low.
 
A 4th order bandpass is mainly a sealed box. The sealed chamber will have a certain peak resonance based on the sub’s parameters and the size of the box. The ported section is almost always used to boost the peak Fc of sealed or to boost higher frequencies. The sealed side is your low tuned side in a 4th BP. The front ported chamber on a 4th works way differently than a regular ported box would. For example, with the sealed being the low tuned side, I’ve done a 4th tuned to 43 hz and the whole bass system peaked at 28-29 hz due to the low frequency of the rear chamber. The front chamber on a 4th is simply a booster chamber for the rear, and it’s usually tuned at Fc of sealed or higher, because putting any enclosure as a rear and having a front chamber with port will make the rear chamber tuned lower, due to the rear sound having to pass through a longer pathway to exit the box vs a regular sealed box or regular ported (vs a series 6th BP). Many people for daily with 4th’s tune the front to 45-50 hz. The main thing is to make sure your subs play low enough in sealed not to get choked out on the lows, because that can happen regardless of where the front chamber tuning is at.
I actually understand that! And kind of one of the reasons I want to do fourth order because that would leave me enough room to place my amplifiers on the box itself, because I am limited in the space that I have in my Kia soul
 
I actually understand that! And kind of one of the reasons I want to do fourth order because that would leave me enough room to place my amplifiers on the box itself, because I am limited in the space that I have in my Kia soul
I hope you didn’t misInterpret my last message.. I was excited that I actually understand what you’re talking about… Lol! I will level with you. I am a handyman, I work for myself, I am not well off by any means. I actually had to splurge to get the speakers, the upgraded alternator, the upgraded battery… and I’ve researched everything I know how, and used every free application there is to try and design this box. And I come close… But I’m not getting exactly what I need. So… I am asking… No, I am begging.! is there anyway you can please help me?
 
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