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tinitus 6th August 2007 09:58 AM

3way with bandpass sub
2 Attachment(s)
Hi, just got this crazy idea

With a coupled cavity 6th order bandpass sub 20-50hz is possible, driven by its own amp

Topsystem consist of 12" and 5" and tweeter, mostly because I have the drivers

Well, I know enough to realize that this wont work, on the other hand I am tempted to try:clown:

sreten 6th August 2007 10:08 AM


You've lost me, that is not a "coupled cavity bandpass" sub.

If your actually talking about a double box reflex, I'm not convinced
about the methodology for a given total box volume at all, a better
driver choice seems more effective, but the DBR seems to allow a
very low Qts driver to work in big boxes in a fashion.


tinitus 6th August 2007 02:19 PM

It is what you seem to call a DBR .... well, I maybe should have said 4way, and you are right about the big volume, its around 130 liter for the sub alone, and the additional 12" midbass will need another 60 liter minimum, so yes its a big one

what is tempting, at least to me, is the very low cut off(drivers Fs/18hz), and narrow passband with upper limit around 50hz

Subdriver has low Qts=0.19 and Fs=18hz ... its a 92db SPL and Xmax may be a little small at around +/- 6mm (?)

How much Xmax do think is needed for this DBR sub going down to 20hz ?
How is rolloff below 20hz ... will it get "unloaded" ?

sreten 6th August 2007 05:05 PM


Nope its not a DBR. That would only have the 12".

So there is a 15" lurking inside the bottom box ?
6th order BP has 2 vents, 4th order BP the 1,
the difference being the rear being vented or sealed,
the front always being vented.

Cannot really see the point for the sub over normal sealed or vented.


tinitus 6th August 2007 07:51 PM

Ok, but there is a 12" inside the bottom box with double chambers and two ports ... drivers backside is portet into the front chamber, so it should be 6th order allright, hence the narrow passband

The advantage over normal BR ? ... 18hz with a low Qts driver :D

I reckon that impulse behaviour cant be any worse than normal portet or various TL ... actually I have heard a very cheap 4th order bandpass sub play quite nice

DorinD 7th August 2007 08:37 AM

Go for it!
I am using a 6th BP for sub-bass duty high-crossed @80Hz and it's very convenient for me because it's not muddying my subhorns (80-400Hz) which seem to radiate the full bass spectrum (sub-bass included).
The low distorsion figure and eficiency of 6th BP aligment is the main advantage, the second been the low off-band energy. But the second advantage must be complemented by good midbass channels.

sreten 7th August 2007 08:41 AM


Originally posted by tinitus

The advantage over normal BR ? ... 18hz with a low Qts driver :D

... actually I have heard a very cheap 4th order bandpass sub play quite nice


Please gives specs of said driver that works better in a 6th order ....

You are correct in that a correctly designed BP the low pass section
is equivalent to a 2nd order LP filter - fixed frequency - if this is
correct it will work well with high power handling before cut-off.


tinitus 7th August 2007 10:33 AM

Thanks fore good response, but I now see a minor problem

The 12" midbass in closed box with shallow rolloff slope may result in too much overlap on the sub ... well, I think it may cause problems, not really sure but it might be a bit tricky to get smooth response

At the moment I use double 8" in closed and it gives me plenty bass and good lowend too, sounds very nice but I still miss the lowest sub region so I am still very tempted by this

Sreten, this would be the "sub" driver ... what I like is the low Fs=18hz with only 100gr. mass, and the low Qts ought to give good controll

tinitus 7th August 2007 11:31 AM

I think I might have solved the problem with the bandpass sub integration with the midbass overlap

Ofcourse, as I said earlier the sub will need a seperate amps ... with room gain the sub will need some level attenuation, so the drivers might actually blend very nicely

sreten 7th August 2007 11:57 AM

2 Attachment(s)

shown is said driver with 17.5L sealed, 35L reflex and 90L 6th BP.

The BP is incredibly sensitive to port tuning, very large, gets nowhere
near 18Hz, and is pretty much an in room boom box in my terms.


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