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 14th August 2012, 02:46 PM   #1
Astera is offline Astera  United States
diyAudio Member
 
Join Date: Dec 2005
Location: CA
Default Passive Radiator - Enclosure Volume

I picked up a Dayton Audio SD270A-88 10" DVC Subwoofer and a couple of matching passive-radiators to play around with.

I built a small, unusual polyhedral enclosure but I calculated the volume of my enclosure is less than a cubic foot.

The Vas for the 10" DVC is 3.8 cu ft.

I'm new to subwoofer design - even more so to passive radiator systems: does this thing have even a chance to fly?

Is the Vas to be treated as the recommended enclosure size to "balance" the driver? If I'm so wildly small in volume, can this be made up for by adding additional mass to the passive radiators? What is the effect of having too small an enclosure?
  Reply With Quote
Old 14th August 2012, 05:17 PM   #2
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
no, not good.

It is basically a ported design.
So you can run the "numbers" in any of the free or shareware box simulation programs and see the results for yourself...
...the effect of a PR is not exactly the same as a port, but close enough to see what is likely to result.

You can make it work two ways:
A) set the PR [i] up in frequency [i] to near where the 10" sub is going to naturally work in a small volume
or
B) set the PR down where you want it (say 35Hz.) and live with the dip between the 10" response in the box and where the PR works - the PR will also be lower in level.

there is a (C), equalize the dip, set the PR down to the intended F3 point (maybe 30Hz would be ok, and that is lower than you think) and live with the reduced SPL and power eating of that set up... you also need a HP filter below the PR freq...

Probably better to just EQ the 10" in the small box, and stuff it fully at that point... gotta run the numbers for max SPL and excursion vs. power and extension...

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 14th August 2012, 05:34 PM   #3
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
This driver needs about 4cu.ft for a br alignment with a Fb=23Hz and F3=26Hz.

Doh... was going to post the Fb and F3 with a 1cu.ft enclosure and the program crashed... don't feel like typing all the params in again.
__________________
"If you don't like funerals don't kick sand in Ninja's face." - Ninja
  Reply With Quote
Old 16th August 2012, 04:46 PM   #4
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
aim for 32-35Hz. you will get a decent result, and maybe a not tooo large a box, reasonable max SPL and will sound very good.

_-_-bear

PS. you only need to type in the box volume, VAS, Qt, F3 and Port freq...

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 16th August 2012, 09:25 PM   #5
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi Astera,

Post #1: "...What is the effect of having too small an enclosure?"

In the extreme case you end up with a transmission line enclosure. The free volume of the enclosure becomes a coupling chamber, and the passive radiator becomes the transmission line (duct or pipe). This can be modelled in Martin J. King's MathCAD spreadsheets, or (without the stuffing) in Hornresp. bjorno is the expert on this subject, I think he calls his design's MLTL and OD-MLTL, etc. (for mass-loaded transmission line and Offset-driver mass-loaded transmission line). I would recommend you search for bjorno's posts on this subject, but be warned that it can become a little deep quickly. Just thought I point it out while you're asking.

Basically, bear has you on the right path with the vented passive radiator enclosure.

Regards,
__________________
Oliver
  Reply With Quote
Old 20th August 2012, 05:21 AM   #6
Astera is offline Astera  United States
diyAudio Member
 
Join Date: Dec 2005
Location: CA
Thanks.
  Reply With Quote
Old 21st August 2012, 02:18 PM   #7
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi Astera,

A software you might find applicable for your design is Jeff Bagby's "Woofer Box and Circuit Designer", an Excel based spreadsheet application that is especially usefull for passive radiator systems:

jbagby

Regards,
__________________
Oliver
  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
Enclosure question - active 3way (passive radiator or not?) firefart_1st Multi-Way 16 17th May 2011 11:23 PM
Passive Radiator and Sub Enclosure Vibration dwell Subwoofers 10 23rd January 2008 04:08 PM
Passive Radiator Fazorcat Subwoofers 42 10th May 2006 07:05 PM
passive radiator ??? Ahmad_tbp Multi-Way 20 29th March 2005 07:44 AM


New To Site? Need Help?

All times are GMT. The time now is 07:48 AM.


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