CARSOUND.COM Forum
Old 05-24-2001, 02:12 AM   #1
courtland
 
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Where can I find out about the more complicated box styles? One of my friends has a 7th order bandpass with 2 8's, and it sounds pretty good. He said it was seventh order. Each sub had its own box ported into a single sealed box between them. I don't think there were any ports to the outside. This sound to me like its just a sealed box. He knows pretty much, but he doesn't learn from this forum, so how much can he know? (j.k.) What are the advantages of complicated bandpass? I figure its either more efficiency, which I've heard is false. Or it is more SQ.
 
Old 05-24-2001, 03:44 AM   #2
clean&low
 
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usualy when considering a bandpass box its because of effeciency. They usualy are not built for sound quality although I have heard a few that have sounded quite good.

If you are into car audio you probably know about class D amps. They only play up to about 250-500hz as opposed to a class A/B which plays to about 25,000hz. Since the class D plays a very limited bandwidth it is much more effecient. The same is true with a bandpass. The ported box in front of the woofer acts as a highpass crossover so the box starts to roll-off much quicker than a sealed or a ported box. And thus giving the bandpass a large advantage when it comes to pure output.

You wern't totaly clear when you described your friends box but here are the breakdowns.

5th order or single reflex bandpass has a sealed chamber that fires into a ported chamber.

7th order or dual reflex bandpass has a ported chamber firing into another ported chamber.
 
Old 05-24-2001, 04:26 AM   #3
courtland
 
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the more I think about it, the more it sounds like just a weird sealed box. He had to chamber each with a sub firing into one single sealed box in between them.

[This message has been edited by courtland (edited May 24, 2001).]
 
Old 05-25-2001, 06:44 PM   #4
R-P
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Location: Netherlands
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Quote:
Originally posted by courtland:
the more I think about it, the more it sounds like just a weird sealed box. He had to chamber each with a sub firing into one single sealed box in between them.
I have a ready made 7th order bandpass with two 8"ers. ($40, and doesn't even sound that bad, plus you cannot poke into the woofers, so ideal for litteraly throwing into the car)
The subs are clam-shelled together ('isobaric') and have a ported room at the back of each speaker, so two 'enclosures' (and a third tiny one between the speakers).
I'm pretty sure that's 7th order bandpass, but I wouldn't know what speakerbuilding-programs can calculate this.

Mormal bandpass shouldn't be a problem though. Plenty of info and speakerbuilding programs on that.

Have fun,
R-P
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Old 05-25-2001, 07:19 PM   #5
courtland
 
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heres what his box looks like:

_ __________ ___
|\____/ | __| \____/ |
| | __ |
| |__ | |
| __ | |
|________|_____|_________|

notice, nothing ports to the outside, and the subs are only half in the box, like a ported or sealed. Isn't this just a sealed box?
 
Old 05-25-2001, 08:47 PM   #6
Colin
 
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Okay despite the fact that ASCII art doesn't work i get what you mean.
At high frequencies, the sub sees a small chamber, so it pays "tight" and "quick"
As the frequency played lowers it can see the middle chamber, so it sees a bigger box, giving lower extension.
You can actually port the middle chamebr as well, and then on top of that you can port the first chamber to create an ABC box, so there are a lot of configurations available. I don't think that they all have names though. I know a friend with a similar setup over here, but the middle chamber is ported. It's not really a regular bandpass, but is sort of like series tuned in a way.

Colin

------------------
Click here to visit my page on horn boxes
 
Old 05-26-2001, 12:21 AM   #7
meth23
 
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Isn't 7th order a box where there are two "boxes"/"enclosures" where one has a sub and the other doesn't. Each of these are ported to the outside and there is also a port going between the two enclosures. If so, it sounds like an ABC (Aperiodic Bi-Chamber) Box. Check out termpro with their search engine to find some good articles on these enclosures. Supposed to be loud, play about 1-1.5 octaves with good SQ.
 
Old 05-26-2001, 02:25 AM   #8
clean&low
 
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Hey Meth,
If it is two ported boxes it is a 7th. order if it is two ported boxes with a port conecting the two boxes then its an ABC
 
Old 05-26-2001, 10:26 AM   #9
Colin
 
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Why is it 7th order and not 6th order?

Colin

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Click here to visit my page on horn boxes
 
Old 05-26-2001, 01:40 PM   #10
Tuttle
 
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Seventh order systems are a sixth order units with an inductor capacitor or resistor in line. Typically a seventh order system is a (parallel ported) sixth order bandpass box with an inductor in line to it. It is possible to use a capacitor in line instead, to decouple the amplifier's damping, but since there is not much useful documentation of this technique, we always modeled it, then fiddle with the value until we got the curve we wanted.
Fifth order, predictably enough, is a fourth with an in line passive element. The benefit of this in-line inductor approach is a better cut-off of out-of-band noise, reducing the garbage that bounces out through the port. Using capacitors, 500 to 2,500 uf is the most useful range, at at least 100 volts. Motor starting capacitors do the job handsomely, and are cheap as hell.
 
 


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