Can you use 2x 4th order BP boxes to imitate a 6th order BP ? - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th January 2012, 11:26 PM   #1
diyAudio Member
 
RobWells's Avatar
 
Join Date: Aug 2002
Location: UK
Default Can you use 2x 4th order BP boxes to imitate a 6th order BP ?

I'm working on a tiny sub to blend in with cabin gain in a car. The perfect option is a 6th order BP rolling off at 24dB/oct from 70Hz down (vehicle has a 20dB boost at 42Hz)

However, I'm thinking the cone will unload below 70Hz and may be a problem so was wondering if I could replicate a 6th order BP with a pair of 4th order boxes, with tiny sealed back chambers. (sealing them will prevent them from over excursion below tuning)

I've attatched a pic to show what I'm trying to achieve.

I guess the pair of 4th order subs would be wired out of phase to act like the 6th order one ?

Thanks,
Rob.
Attached Images
File Type: jpg bpq.JPG (84.6 KB, 128 views)
  Reply With Quote
Old 20th January 2012, 12:20 AM   #2
Zero D is offline Zero D  United Kingdom
diyAudio Member
 
Join Date: Aug 2009
Hi, i see what you're trying to achieve by using 2 x 4BP

Quote:
rolling off at 24dB/oct from 70Hz down
I think you mean rolling off from 70Hz up

Why do you think the cone will unload below 70Hz ?

Can you provide the driver Make/Model # & TS ?

Quote:
I guess the pair of 4th order subs would be wired out of phase to act like the 6th order one ?
Why do say they are or would be wired out of phase ?
  Reply With Quote
Old 20th January 2012, 12:31 AM   #3
diyAudio Member
 
RobWells's Avatar
 
Join Date: Aug 2002
Location: UK
Quote:
Originally Posted by Zero D View Post
Hi, i see what you're trying to achieve by using 2 x 4BP



I think you mean rolling off from 70Hz up

No - I mean rolling off from 70Hz down - take a look at the graph I posted

Why do you think the cone will unload below 70Hz ?

It's in a vented alignment - below tuning they are unloaded.

Can you provide the driver Make/Model # & TS

Elemental designs 7kv 6" subwoofer. Too late to post all the specs. tbh my question is generic and will apply to all drivers / boxes.



Why do say they are or would be wired out of phase ?

Because in a 6th order box the 2 chambers are driven out of phase to one another.
  Reply With Quote
Old 20th January 2012, 01:12 AM   #4
Zero D is offline Zero D  United Kingdom
diyAudio Member
 
Join Date: Aug 2009
Quote:
No - I mean rolling off from 70Hz down - take a look at the graph I posted
Ahh, right you want 60/70Hz - 100Hz

Ok, not much bandwith there, but sure it'll make a difference to having none

Quote:
It's in a vented alignment - below tuning they are unloaded.
If you have a HPF in place @ 60/70Hz you'll be fine

Quote:
Because in a 6th order box the 2 chambers are driven out of phase to one another.
But they will be tuned to different Frequencies, so add rather than cancel Have a look at these links for more info.

Quote:
but they are 180 degrees out of phase with each other so if you tune them to the same frequency they will almost perfectly cancel each other out. The two chambers have to be tuned to different frequencies so they sum effectively.

https://sites.google.com/site/amateu...holtz/bandpass
  Reply With Quote
Old 20th January 2012, 09:47 PM   #5
diyAudio Member
 
RobWells's Avatar
 
Join Date: Aug 2002
Location: UK
Quote:
Originally Posted by Zero D View Post
Ahh, right you want 60/70Hz - 100Hz

Ok, not much bandwith there, but sure it'll make a difference to having none


It will be flat in car from 40Hz - 150Hz. That's not a bad bandwidth



If you have a HPF in place @ 60/70Hz you'll be fine

If I use a HPF it will change the response and not blend in with the cars cabin gain Maybe that's why I'm asking the question in the first place



But they will be tuned to different Frequencies, so add rather than cancel Have a look at these links for more info.

I'm perfectly aware of how a 6th order bandpass box works thanks.
  Reply With Quote
Old 20th January 2012, 09:51 PM   #6
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Rob, can you use open and close quote strings, ( [/qu0te], [qu0te]), so we make sense of your replies without scrolling up and down please.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 20th January 2012, 10:11 PM   #7
diyAudio Member
 
RobWells's Avatar
 
Join Date: Aug 2002
Location: UK
I'll do my best Al,

Any thoughts on my actual question ?

Cheers,
Rob.
  Reply With Quote
Old 20th January 2012, 10:37 PM   #8
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by RobWells View Post
I'll do my best Al,

Any thoughts on my actual question ?

Cheers,
Rob.
Measure the t/s parameters of that eD driver before you commit to any design, particularly one that's quite sensitive to t/s parameter variations.
__________________
www.diysubwoofers.org
  Reply With Quote
Old 20th January 2012, 11:19 PM   #9
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Blog Entries: 8
I'd try them wired in phase then out of phase. One will likely sound better than the other. I would be interested to know which one it is (in or out of phase).

It is an interesting question, nothing like what I've seen before. Go for it, and if it doesn't work out, you could always use a generic sealed box (but where's the fun in that?)

Chris
  Reply With Quote
Old 20th January 2012, 11:37 PM   #10
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Quote:
Originally Posted by RobWells View Post
...Any thoughts on my actual question ?
I'm not really an authority on bandpass designs, so can't really comment, but I completely understand your worries about unloading. In my limited experience I would really recommend a high pass filter if you're running them that high. Have you thought about a three chamber fourth order bandpass? That might be easier to get working, and sound more musical than the sixth order.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
1st order to 4th order conversion Professor smith Multi-Way 22 28th November 2011 11:41 AM
4th BP experts? danielm Subwoofers 4 20th July 2009 05:47 PM
My 1st order butterworth filter better than 4th order L-R: Why? philipreji Solid State 61 1st March 2007 05:50 PM
Help in measuring response of 4th order BP box venki Subwoofers 13 14th November 2005 10:45 PM
Building my first 4th order BP box, any suggestions? theCat Subwoofers 8 23rd May 2005 05:01 PM


New To Site? Need Help?

All times are GMT. The time now is 05:59 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2