Question regarding bandpass enclosure - 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 14th October 2008, 08:34 PM   #1
wrankin is offline wrankin  United States
diyAudio Member
 
Join Date: Mar 2003
Location: Durham, NC
Default Question regarding bandpass enclosure

Hey gang,

I recently picked up a set of Boston Acoustics SubSat 7's cheap on Ebay. The system consists of a pair of small 2-way satellites and a passive bandpass subwoofer. I had a quick question about the layout of the subwoofer.

Being the eternal engineer, I of course didn't even bother plugging the subwoofer in and immediately took the back of the cabinet off to check out the guts. Internally there are two decent looking 6-7 inch woofers each with their own sealed enclosure. The drivers then radiate into the third enclosure which contains the tuned port.

The one thing I did notice is that one of the woofers is installed "upside down" (ie, with the basket extending into the tuned chamber) while the other driver has its basket in the sealed portion. This was obviously an intentional part of the design, and the two drivers are wired in opposite phase.

So, why did they do this? Is it an effort to reduce distortion?

Thanks,

-bill
__________________
Bill Rankin
  Reply With Quote
Old 14th October 2008, 08:51 PM   #2
diyAudio Member
 
Join Date: Feb 2004
Location: Queensland Australia
Yes, I think you are correct in assuming it is distorion that is the factor they are trying to address. As I understand it people think that the characteristics of the cone movement are different going away from the magnet assembly compared with moving towards it and mounting any pair of woofers in the manner described will aid in cancelling some of the anomolies. But others may have a more technical/competent answer. BTW, I know how you feel. Always have a look inside before playing!!!

Jonathan
Edit; Yup, just read your post again. If the enclosures are sealed then there will be a difference on the surounds/suspension etc because the air on the inside will be in compression for movement in one direction and then be expanded in the other. There will be a mild variation in the characteristics.
__________________
"It was the Springtime of the year when aunt is calling to aunt like mastodons bellowing across primeval swamps." P.G. Wodehouse.
  Reply With Quote
Old 15th October 2008, 12:30 PM   #3
diyAudio Member
 
technofreak's Avatar
 
Join Date: Dec 2006
Send a message via MSN to technofreak
I'm using push-pull myself - cheap Visaton BG20 8" fullrangers that's midrange turned out not to be so good, too high harmonic distortion for my liking (though subjectively with music not that bad), now playing up to ~250 Hz in push-pull, for the time being providing bass to complement Eminence Alpha 6 midrange. I can run those Visatons beyond their X-max, no noticeable distortion whatsoever.

IMO push-pull is a very good and easy substitution for horn-loading if you want to reduce distortion at bass frequencies. It don't work for midrange/highs, though, because drivers must be within 1/4th of wavelenght.

As noted in prev. post, push-pull evens out the magnetic field* and suspension differences of the "+" and "-" side of cone excursion, reducing 2. harmonic distortion.

*Shorting rings do the same, but they're more effective at higher frequencies, whereas push-pull is more effective at lower frequencies.
  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
Bandpass Enclosure & Baffle Step 69stingray Multi-Way 2 12th July 2007 01:02 AM
help with a bandpass enclosure idahoxj Car Audio 4 5th July 2005 08:56 AM
bandpass enclosure. What are the pros & cons?NT Lito Subwoofers 12 17th June 2004 05:32 PM
Calculating volume - bandpass enclosure avatar307 Subwoofers 6 14th December 2003 01:59 AM
bandpass enclosure woofer selection Opie Multi-Way 1 21st September 2002 07:57 PM


New To Site? Need Help?

All times are GMT. The time now is 10:32 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