Trying to simulate 4th order bandpass. Some help needed please....

[Naveenbnc]

Hi All,

I am trying to simulate 4th order bandpass for a 10" driver.

I am unclear about three parameters. (please see the attached images)
1. SYSTEM DAMPING FACTOR (DF)
2. SYSTEM TOTAL Q (Q't)
3. VENT LOSSES (QLv)

Are there any ideal values for SYSTEM DAMPING FACTOR and SYSTEM TOTAL Q? Are those variables to keep changing and trying different response graphs?

Any maximum and minimum limits for those? Do they depend on driver TS parameters? Can any one throw some light please....

Secondly, assuming the overall enclosure is perfectly sealed without any leakages, what should be the value of VENT LOSSES? (7 to 15 as far as I know)

Thanks a lot for any help...
Regards
Naveen

 

[diyaudio]

Use Unibox, its straight forward. First provide the driver parameters, then provide the box parameters in the bandpass section. It generates all the relevant curves.

 

[diyaudio]

See the overdrive at diyaudio
https://www.diyaudio.com/forums/subwoofers/325828-overdrive-10-pr-bandpass-sub.html

 

[Hari Iyer]

I have listened to two bandpass design - one from Bose and other from Lithos, both were very boomy.

 

[diyaudio]

I have listened to two bandpass design - one from Bose and other from Lithos, both were very boomy.

Will replacing with a ported or even sealed sub correct the boom in that room?

Boom is not caused by sub or its alignment, its the room modes that causes the fastness or slowness or boominess. Choosing a sub by alignment is sub optimal. A good sub setup measures same, sounds same and 'feels' same irrespective of alignment.

 

[Naveenbnc]

actually this article has all the needed formulae for 4th order bandpass.
http://audiojudgement.com/4th-order-bandpass-design/

When I applied these formulae for my driver, and I ended up with 5.4L and 6L volume for front and rear chambers.
These volumes are pretty small for a 10" driver. So I wanted to cross verify by simulating it.
There I was stuck with the 3 queries I asked in the post #1

 

[diyaudio]

This is what I get using Unibox. 4 ohm driver 100 watts RMS.

Frequency response:-

Cone Excursion at rated power :-


Vent velocity at rated power :-

Not shown is port resonance artifacts

 

[Naveenbnc]

WOW ....
Is this for my driver ??? Thanks a lot @diyaudio
I have to try this Unibox as soon as possible.

 

[diyaudio]

Yes, its using your 10" provided specs, do note that the ported chamber is about 4.35 lts and port itself occupies 1.7lts.
The sealed chamber volume determines the lower cut off. The ported chamber's volume determines the bandwidth.

 

[Naveenbnc]

I have to download and get familiar with this unibox....
But as a quick update with the given volumes, the overall enclosure is pretty compact !!!
Closed chamber is 11L and Vented chamber is 5L (excluding the driver volume, port volume, and bracing)

Please see the attached image for the model as per scale.
Port won't fit in, and the vented chamber is only 2.5" deep.

I know we can play around further to balance port length and dia etc.
But if this band pass allows to build a compact enclosure.... its really interesting!!
I can bend the port 90 degree inside if needed.

 

[Naveenbnc]

well.... this may not be the right method to go ahead ....
But I build it without much of calculations.

One gentleman by name Dr.Ajith built it with 22"x12"x12" overall enclosure size, and said the result was good ...
He used 1:1 ratio of sealed and vented volumes ....

I built it with 1.5:1 ratio for vented and sealed volumes.
And the idea is to do trail and error tuning on port length.
(testing not done yet, since i have been travelling a bit.... please see the attached pics )

the fun part I loved about this build is .... I added a cutout to see the driver excurtion and added a 12mm thick glass behind

 

[sachu888]

Looks really good. There are so many beautiful speaker builds here. It would be good if we have sub forum under DIY for speakers.

Regards
Sachin