3way with bandpass sub

[tinitus]

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

 

[sreten]

Hi,

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.

/sreten.

 

[tinitus]

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]

Hi,

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.

/sreten.

 

[tinitus]

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

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]

Tinitus,
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.
Cheers,
Dorin

 

[sreten]

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

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

Hi,

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.

/sreten.

 

[tinitus]

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

http://www.monacor.dk/produkter/hoejttalerenheder-hifi10-12/vnr/101830/

 

[tinitus]

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]

Hmmm..........

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.

/sreten.

 

[DorinD]

... is pretty much an in room boom box in my terms...

I think that is supose to be, a boom box of clean fundamentals. Armonics of these are the job of other drivers.

 

[tinitus]

Firstly driver VAS is 225 liter

Second, you got the calculations of the design wrong ... it looks like this

With a Qts=0.19 I can hardly believe it will be a boom box

The software I use tells me that the passband will be 18hz - 50hz

DorinD, I am not sure I understand the meaning of your answer ?

 

[sreten]

Firstly driver VAS is 225 liter

Second, you got the calculations of the design wrong ... it looks like this

With a Qts=0.19 I can hardly believe it will be a boom box

The software I use tells me that the passband will be 18hz - 50hz

DorinD, I am not sure I understand the meaning of your answer ?

Hi, that layout sshould not make any difference, Vas is not wrong, sreten.

 

[tinitus]

Looks different to me ... and I dont know why different software say something different

What you say is that low end rolloff is nothing different from ordinary BR ?

 

[tinitus]

If thats the case I might as well make it a closed 100liter, and loose 6-12db from 50-20hz, with active filter

Doesnt look so tempting now my midbass with higher Qts might do that better on its own, allthough it does have Fs of 18hz

 

[DorinD]

Tinitus,
my observation to Sreten comment just says that a "boom-box" character of a sub-bass is not a bad thing but the norm. A sub-bass channel perform only the lowest fundamentals, so the lack of armonics aleviate any "color" or special tone to the sound. Like an uni-tone or boom-box.

Not the same character could be expected from a closed of BR sub box. These, because of their large bandwidth, can perform a lot of armonics (to some hundreds Hz) from the musical program and their distorsions products. So, their sound is much colored and capture much of the bass instrument's tone.

 

[tinitus]

OK, still thinking

Well, we all know that midrange sounds better if the driver is relieved from bass duties
The same thing might apply to a midbass driver relieved from the lowest frequency

 

[tinitus]

New problem ... my 12" midbass woofer is too good, and goes too low ... too much overlap with sub

New, wiser, different and smaller design

Still 6th order bandpass sub, but now with 8" ... and now with a 2way top with a 6" and tweeter ... pretty ordinary, allmost ... topic smashed

drivers could be these, and they are all together cheaper than the planned sub driver

http://www.monacor.dk/produkter/hoejttalerenheder-hifi6-9/vnr/101810/

http://www.monacor.dk/produkter/hoejttalerenheder-hifi6-9/vnr/104250/

Well, I wanted BIG, so this is not gonna be ... maybe some other time


Thanks guys!

 

[tinitus]

Before final closing, I would like to ad that this Legend B102 might be nearly perfect fore the big 3way
fore some time I have been thinking of a way to use this driver, and that could even be a 2way with a ribbon like the Hivi RT8II ... and the 6th order passband sub should blend nicely ... and just a simple 2way xo ... and nice efficiency ... maybe in my dreams

http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-495

Cheers

 

[jamikl]

Sorry if I'm thick but there is one thing I don't understand in this thread. Sretens diagram shows the speaker unit coupling into the front chamber and BOTH PORTS coupling to the room. Tinitus' diagram shows the speaker coupling to the front chamber, a port coupling from the rear chamber to the front chamber and only the FRONT CHAMBER PORT coupling to the outside air. This is similar to another speaker discussed somewhere, I don't remember where. that had a variovent between the two chambers.

Is there a difference in the performance of the two speakers laid out as shown?
jamikl