So I was discussing 6th order bandpass boxes with someone on another forum and the question came up, just what is the difference in performance between series tuned and parallel tuned boxes?
If you had two boxes with the same chamber volumes and tunings but one was parallel tuned and one was series tuned would they sound any different?
My understanding is that they would sound the same since once you get below the front chamber's tuning frequency the port unloads and then begins to function as part of the rear chamber's port once you get closer to the rear chamber's tuning. Or am I completely wrong and don't know what I'm talking about? That's happened before.
Any input will be greatly appreciated!!!
If you had two boxes with the same chamber volumes and tunings but one was parallel tuned and one was series tuned would they sound any different?
My understanding is that they would sound the same since once you get below the front chamber's tuning frequency the port unloads and then begins to function as part of the rear chamber's port once you get closer to the rear chamber's tuning. Or am I completely wrong and don't know what I'm talking about? That's happened before.
Any input will be greatly appreciated!!!
I'm trying to remember20 years back - seems like when I did a few sims of equivalent response curves of both types in a fixed volume that the chamber volume distribution was different (?) In a way I like series BP as just tuning the front chamber is enough to get something flat, (I have very little experience so leave the good answers to others)
Can you show some diagrams as to what you mean? I think parallel has both chambers vented to outside. I know that the XKi is quasi 6th order but not sure that is the same as series 6th order. The ideal tuning is usually front chamber half volume of rear. For XKi I make it smaller to keep aperture closer to driver for full range like operation and avoid echoing sounds. I think smaller front chamber allows higher upper bandwidth cutoff.
Series tuned effectively takes a BR box and feeds that into a ported box. One chamber feeds another. Your outer ports need to be huge to avoid chuffing.
You can stagger the tunings (lowest inside) to get a usefully wide bandwidth, or tune the ports to the same frequency to get skull-crushing bass at one frequency. Note that the cone would be held very still at that frequency, so I hope your driver has lots of thermal mass.
Having one port feeding into another means the inner port can have wind noises, which will mostly be masked by the 2nd port.
Parallel-tuned boxes have a port outlet from each side of the driver to the rest of the world, and is what I'd consider a "standard" 6th order bandpass.
Smaller ports can be used since you're not sticking all of your signal down one pipe.
Both methods mask driver distortion in favour of port noise/compression. You can, therefore, use relatively cheap drivers and still get reasonable sound, so long as the frequency response comes out okay.
Note that its important to be careful with bandpass boxes - if they start sounding bad, your driver is already history, and has been complaining for a while.
Chris
You can stagger the tunings (lowest inside) to get a usefully wide bandwidth, or tune the ports to the same frequency to get skull-crushing bass at one frequency. Note that the cone would be held very still at that frequency, so I hope your driver has lots of thermal mass.
Having one port feeding into another means the inner port can have wind noises, which will mostly be masked by the 2nd port.
Parallel-tuned boxes have a port outlet from each side of the driver to the rest of the world, and is what I'd consider a "standard" 6th order bandpass.
Smaller ports can be used since you're not sticking all of your signal down one pipe.
Both methods mask driver distortion in favour of port noise/compression. You can, therefore, use relatively cheap drivers and still get reasonable sound, so long as the frequency response comes out okay.
Note that its important to be careful with bandpass boxes - if they start sounding bad, your driver is already history, and has been complaining for a while.
Chris
Thanks for the info Chris! What you said makes a lot of sense to me. What has been throwing me off is the series tuning info I got here: The Subwoofer DIY Page - 6th Order Bandpass Systems
According to that page the rear chamber tuning is determined by a combination of the front chamber port and rear chamber port, which would make it impossible to tune both chambers to the same frequency, the rear chamber would have to be tuned lower.
What you said Chris and what I read on the page I linked both seem reasonable, but they are contradictory. What's your opinion on the info I linked above?
According to that page the rear chamber tuning is determined by a combination of the front chamber port and rear chamber port, which would make it impossible to tune both chambers to the same frequency, the rear chamber would have to be tuned lower.
What you said Chris and what I read on the page I linked both seem reasonable, but they are contradictory. What's your opinion on the info I linked above?
Hmmm...
I'm not convinced that the two ports work together to tune the rear chamber, as is suggested in that link - I see no physical reason the two ports ought to couple in that way.
That said, the guy that wrote it knows his stuff, so its entirely possible I've missed something. Perhaps someone with more experience can have a look.
Unfortunately, I can't simulate this myself as I haven't got around to learning akabak yet. When I've finished my degree, maybe.
Chris
I'm not convinced that the two ports work together to tune the rear chamber, as is suggested in that link - I see no physical reason the two ports ought to couple in that way.
That said, the guy that wrote it knows his stuff, so its entirely possible I've missed something. Perhaps someone with more experience can have a look.
Unfortunately, I can't simulate this myself as I haven't got around to learning akabak yet. When I've finished my degree, maybe.
Chris
Hi thejessman,
I don't see anything wrong w/ Brian's description, it's probably only a difference in semantics. By definition, the chambers and their tuning cannot be independent.
I found a little paper that explains the different alignment actions in general terms: Basic Operation of the Series Vented Band-Pass Sub-Woofer Enclosure with Pressure Driver Environmental Radiator, by Jeff Anderson & Jason Linse. Here is a link:
http://tara.mmto.org/speakers/theory/series_vented_bandpass.pdf
Regards,
I don't see anything wrong w/ Brian's description, it's probably only a difference in semantics. By definition, the chambers and their tuning cannot be independent.
I found a little paper that explains the different alignment actions in general terms: Basic Operation of the Series Vented Band-Pass Sub-Woofer Enclosure with Pressure Driver Environmental Radiator, by Jeff Anderson & Jason Linse. Here is a link:
http://tara.mmto.org/speakers/theory/series_vented_bandpass.pdf
Regards,
Attachments
like a DCR's inner port, below a certain point - both chamber volumes should be seen. I have a little 10" series in storage with Madisound DVC driver with 28-110Hz bandwidth - foam has to be rotted by now.
a fast alignment program like the old "SpeakEasy" would allow some good comparisons
each chamber was the same size ~1.25 cubic feet - here's an old nearport graph
in the farfield, the little BP's response had some "saddle"
a fast alignment program like the old "SpeakEasy" would allow some good comparisons
each chamber was the same size ~1.25 cubic feet - here's an old nearport graph
in the farfield, the little BP's response had some "saddle"
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I am out of my depth when it comes to series tuned bandpass. I know the tuning of the inner chamber is lowered by that of the outer chamber, so the port lengths of the inner chamber would be shorter than that of a standard box of similar tuning ported to the outside world.
I'm unfamiliar with trying to find the Helmholtz frequency of the inner box. I did try in Hornresp to model it as a ported pipe feeding into a secondary cavity with a ported pipe to the outside world.
Working out the phase difference between this and how just the front chamber behaves is where my brain turns to mush. AFAIK I haven't found a way to simulate a series tuned bandpass in Hornresp.
Parallel bandpasses are easier to me.
There is a Bose enclosure that feeds both ports of a parallel tuned bandpass into a common ported series tuned outer chamber. I can't get my head around this or even know if it sounds good.
I'm unfamiliar with trying to find the Helmholtz frequency of the inner box. I did try in Hornresp to model it as a ported pipe feeding into a secondary cavity with a ported pipe to the outside world.
Working out the phase difference between this and how just the front chamber behaves is where my brain turns to mush. AFAIK I haven't found a way to simulate a series tuned bandpass in Hornresp.
Parallel bandpasses are easier to me.
There is a Bose enclosure that feeds both ports of a parallel tuned bandpass into a common ported series tuned outer chamber. I can't get my head around this or even know if it sounds good.
The information on that page actually reflects a discussion that was held with Tom Danley about series-tuned 6th order bandpass alignments on this forum.
Thanks for posting Brian. I have found your site to be very helpful. Do you have a link to that thread? I would really love to read it!
Good Lord - that was over four years ago
. A search here should bring it up, if it's still around.
Good Lord - that was over four years ago
I searched for the thread quite a bit, but wasn't able to find it. Thanks for your help none the less!
Good Lord - that was over four years ago
That would be a very interesting read if someone can find it.
I have always found the bose design very interesting.
Apparently the drivers in there are not the best either. But the extra time spent on the box design paid off.
This is all good stuff and confirms why I am using series 6th order bandpass to provide wide bandwidth, cone motion control, and reduction in harmonic distortion of the driver for my XKi design.
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass.html
A 6th order series tuned bandpass script in akabak is very simple - it could literally be done in 8 or 10 lines of code. I will post when I get a chance.
The tuning freq overall is definitely linked together - it is a coupled system by definition.
I am seeing very low harmonic distortion over a wide range as cone motion is so small. Will post data when I get everything together.
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass.html
A 6th order series tuned bandpass script in akabak is very simple - it could literally be done in 8 or 10 lines of code. I will post when I get a chance.
The tuning freq overall is definitely linked together - it is a coupled system by definition.
I am seeing very low harmonic distortion over a wide range as cone motion is so small. Will post data when I get everything together.
Recent results in Beta 8cx XKi.
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass-13.html#post4207345
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass-13.html#post4207345
Hi Y'all,
When I type "bandpass" and "Tom Danley" into the advanced search in the subwoofer forum I get:
http://www.diyaudio.com/forums/subwoofers/114340-tapped-horn-dummies.html
Using the same search in that thread (this is a great thread, a must read) I get to Post #208: "...In a band pass filter, one can get gain by using a high pass and low pass filter, if they are under damped and placed close enough in frequency, the mid band area “fills in” with a net gain over the bandwidth. That coupled filter effect ties the BP’s gain to the bandwidth..."
I cannot find the discussion Brian referenced in Post #13.
The AkAbak main manual has a nice example of a series-tuned 6th order bandpass on P.64-71, and following a discussion of their Helmholtz dialog.
The individual elements, e.g.: the rear cavity and the cavity connecting duct are basically the same as you would see in a bass-reflex enclosure, but the loading is quite different, and this holds for just about every element in the simulation.
Regards,
P.S.: chris661 you won't have any problem getting into AkAbak, just use a Hornresp Export Akabak Script and have at it.
When I type "bandpass" and "Tom Danley" into the advanced search in the subwoofer forum I get:
http://www.diyaudio.com/forums/subwoofers/114340-tapped-horn-dummies.html
Using the same search in that thread (this is a great thread, a must read) I get to Post #208: "...In a band pass filter, one can get gain by using a high pass and low pass filter, if they are under damped and placed close enough in frequency, the mid band area “fills in” with a net gain over the bandwidth. That coupled filter effect ties the BP’s gain to the bandwidth..."
I cannot find the discussion Brian referenced in Post #13.
The AkAbak main manual has a nice example of a series-tuned 6th order bandpass on P.64-71, and following a discussion of their Helmholtz dialog.
The individual elements, e.g.: the rear cavity and the cavity connecting duct are basically the same as you would see in a bass-reflex enclosure, but the loading is quite different, and this holds for just about every element in the simulation.
Regards,
P.S.: chris661 you won't have any problem getting into AkAbak, just use a Hornresp Export Akabak Script and have at it.
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