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Discussion Starter #1
I had a fella build me a custom subwoofer. He acquired all of the components. And made built me a little monster. What I know is it is a DD designs motor. Which is gigundis. There is a massive oversized basket that is painted blood red. I know there are 2 different types of spiders installed. And that one of them is a linear spider. I don't know the other. Soft parts are massive. This thing looks like a 12 " sub on roids. And from what I was told by the fella that built it. It is more or less the equivalent of a 12" sundown zv5. I own a truck. And I want one bad *** sub in my back seat. With one big *** amp pushing it. And of course all my other mids and highs. Other amps as well. So my question is this. should I take this beats of a sub that has a rms around the area of 3000 watts. And build a big *** Band pass box? I don't know if you put high power subs into band pass. I was always under the impression that band passes were for speakers that needed a little help getting there. Lol. The sub is currently in a 2.5 cu.ft. ported box. Only have 1200 watts to throw at it right this minute. But I am hoping to change that here sooner then later.

So what are everyones thoughts?
 

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Yes. Look at the Devastator thread on avsforum.com.
 

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Bandpass subs are quite popular in cars and trucks due to their small interiors. Assuming it's properly designed bandpass tends to trap most of the annoying harmonic distortions in the box and only allow what you want to hear out the port. In addition, they have a narrow passband so the cabinet can be tuned to heavily emphasize the midbass and allow cabin gain (due to the small interior) to take care of the lower frequencies.
 

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What do you think Front Loaded Horns and Tapped Horns are...BP4's and BP6's with flared ports.
 

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Both alignments tend to be rather large, but if you have the space to accommodate one it can provide tremendous output. Those are also tricky to design though, so they aren't for the faint of heart.
 

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Discussion Starter #7
Wow. Lots of input. So the majority says yes. So my next question is this. With no theile smalls. How exactly does one come about with a design for a bandpass? 4th order 6th order? I am a proffessiomal carpenter. So the box i can handle. I just need some specs. But im unsure how to go about this.
 

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Without TS parameters I'm not sure it's a wise idea. One of the benefits of bandpass is that the alignment tends to mask distortions, but that comes with a caveat; because nasty sounds are suppressed you can easily push it too far and cook the driver. With the parameters you can design the protection mechanisms to include the correct high pass filter.

Bandpass is probably a bit ambitious because there's a lot of design and engineering involved. You have to size the driver to the rear chamber, front chamber and the exit port/tube being used (length and diameter). That's not easy even for someone who has a lot of experience with subs. Being a carpenter you can obviously build any type of box you'll need, but maybe bandpass isn't the correct choice for your first build? I'm not saying you shouldn't, only that it will be really tough to get right.
 

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Discussion Starter #9
I do agree with you jman. After so many people mentioning it. I thought i would look into the possibility of this happening. And even more so was the question of performance. Thisbthing isba beast already. Would jt be beneficial to throw in a bandpass? I am pretty sure i can get the ts's from my dude that built it. With that said. This is not my first build. Just my first bandpass i have to figure out myself. I am 45. Been making speaker boxes since before i could drive. I am not the best box designer. But if i have specs. I can produce for sure.
 

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(snip) With no theile smalls. (snip)
...and that's the reason I said NO.

With a bandpass design, ALL of the output is through the vent. Use the wrong front volume, rear volume, or tuning, and the result could not only sound bad, it could result in damage to the woofer at higher volumes (because of distortion being masked).

Get the basic t/s parameters and an impedance curve for the driver, and those can be used to produce a good bandpass design for it. (Why the impedance curve? To calculate the semi-inductance parameters for the driver, which could come in handy to determine if the design needs to be retuned to account for the impact of those parameters on the driver's response).
 

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Discussion Starter #11
I feel like designing this box is way out of reach for me. It sounds great in the box ive already made. Just thought i could take it to a new level. But being able to build a box to spec. Is way sifferent then designing a box with lots of different parameters that quite frankly. I know nothing about. Thanks for all of your input.
 

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I did a bandpass symmetrically loaded design some years ago. I had all the T/S parameters and it matched my simulation almost exactly. What I couldn't get passed was the port chuffing noise. It never sounded natural. I then went to just a ported design. Same problem. For a sub I think there are two options: sealed or ported using a passive radiator. For me they are the only options. Most sealed enclosure designs will need some sort of EQ at the lowest frequencies to extend the low end response. These days that is relatively easy to do with the available subs and amps.
 

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Your port was too small. I try to stay below 15m/s air speed to prevent shuffling at max volume.
 

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Not really. The port was 4 inches in diameter which was the maximum size allowed for the enclosure size. Of course going with a much bigger enclosure may have been an option but I was able to stay within the enclosure size I had with a passive radiator. It's basically a Sunfire True subwoofer knockoff.


Sub-1.jpg
 

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Some drivers are just not suitable for bandpass alignments. A good sign of suitability is this: if it's difficult to design a decent vented box for the driver that has a vent that's of sufficient size and length to achieve the desired Fb without the vent suffering from chuffing at higher volumes, ir's probably going to be just as, if not more, difficult to design a decent bandpass alignment for it, for the same reasons.
 
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