The reason why open baffle have a bass roll-off - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

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 6th November 2012, 09:23 PM   #1
aarvin2 is offline aarvin2  Mauritius
diyAudio Member
 
Join Date: Sep 2012
Default The reason why open baffle have a bass roll-off

Hi guys this is indeed a very noob question, but I have read stuff all over the net and on this forum but haven't found any simple explanation of why an open baffle has a low frequency roll off ?

Could someone please explain this phenomenon ?? Graphically please ??

Is it just because the waves from the back of the speaker collide with those of the front of the speaker and cancel out due to their difference in phase ??

Why doesn't it happen with wide baffles ??

Why don't front ported or bass/reflex have this problem?? as they are adding the waves from the front to the waves coming from the back of the speaker via the port


Do open baffle with narrow panels(obviously small speakers 3"-5") or zero-baffle constructions(again using 3" to 5" speakers) which have extended bass exist or it's physically impossible to have bass from them WITHOUT adding an EQ ?


Is the bass from an open baffle speaker sound like a sealed box ?? or is it really something else ?? describe please


Thanks again for your time guys!!
  Reply With Quote
Old 6th November 2012, 09:49 PM   #2
diyAudio Member
 
Richard Ellis's Avatar
 
Join Date: Sep 2006
Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Yes you do have it right...The two waves meet at the the baffle edge out of phase & cancel out....the phenomenon was called Doublet operation or an Acoustic short circuit. The wider the baffle the lower the frequencies of 'cancellation' soon however the width of the baffle becomes entirely too big.
Assuming you want to get it down to 80Hz & have a sub-woofer take over from there......do the calculations & prepare. Often times, Super-sized loudspeakers don't go over too well with our Wives/GFs!!!
Ported enclosures are a whole nother' ball O' wax.

__________________________________________________ ______Rick.......

Last edited by Richard Ellis; 6th November 2012 at 10:08 PM. Reason: typo
  Reply With Quote
Old 6th November 2012, 09:59 PM   #3
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

The waves from the front and back combine and cancel. The bass
rolls off at 6dB/octave, and note that driver excursion doesn't.

(its the most important thing to understand, baffle loss throws
away driver excursion, reducing the drivers SPL capability a lot.)

It happens with wide baffles as well, except the frequencies it occurs
are lower, the transition frequency is lower, so wider baffles have
less baffle loss at a given low frequency than narrower baffles.

Vented boxes do have this problem below the port tuning. Above
tuning the output of the port is in phase with the driver output.
(Consider playing with a toy that is weight on the end of a spring,
moving it up or down slowly it will follow your movements, but at
the clearly obvious resonance, your hand and the weight move in
opposite directions, and if you wiggle it fast, nothing much happens.)

For narrow panels even with EQ extended bass is not possible due to
the ludicrous driver excursion requirements to overcome baffle loss.

Bass from a sealed box is not like an open baffle as it is not dipolar.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 6th November 2012, 10:27 PM   #4
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
Good explanation Sreten.
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 6th November 2012, 10:43 PM   #5
Nanook is offline Nanook  Canada
diyAudio Member
 
Nanook's Avatar
 
Join Date: Feb 2004
Location: Chinook Country.Alberta
Default As usual...

...a good explanation sreten (hi Cal).

One way to increase bass with an OB is to create sides and a top shelf (that can be used as a stand to hold the OB). The modified OB then is a very short "U" with much deeper bass as a result. The great thing about the OB types is that there does not exist box colourations.

The resultant bass produced via OBs is what I would consider "deep" but without much impact. The low frequencies are there, they just don't hit you like a good box type subwoofer.
__________________
stew -"A sane man in an insane world appears insane."
  Reply With Quote
Old 7th November 2012, 12:12 AM   #6
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
You also may want to head over to Linkwitz's site if you want a more rigorousness description, math included.
  Reply With Quote
Old 7th November 2012, 12:22 AM   #7
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
Quote:
Originally Posted by Nanook View Post
...a good explanation sreten (hi Cal).

One way to increase bass with an OB is to create sides and a top shelf (that can be used as a stand to hold the OB). The modified OB then is a very short "U" with much deeper bass as a result. The great thing about the OB types is that there does not exist box colourations.

The resultant bass produced via OBs is what I would consider "deep" but without much impact. The low frequencies are there, they just don't hit you like a good box type subwoofer.
I have to disagree. An OB, be it flat,curved U, H can all have just as severe coloration from the baffle as you do with the baffle closed on itself. If you take an OB to the extreme, as in an IB, I can assure you some very strong bass is possible with the proper driver ( large, stiff suspension ) A point well argued by "The cult of the IB" Management of the impedance is far harder than a compliant box.
  Reply With Quote
Old 7th November 2012, 01:00 PM   #8
aarvin2 is offline aarvin2  Mauritius
diyAudio Member
 
Join Date: Sep 2012
Thanks for the excellent explanation guys !!!! Finally I understood the principles!!!

Special thanks to Sreten and his great analogy You guys rock
  Reply With Quote
Old 7th November 2012, 05:28 PM   #9
diyAudio Member
 
Join Date: Jan 2012
I have been trying to deal with the same issue from the opposite side of the coin.
Namely, too much bass from an OB.
Worried about a potential lack of bass from a pair of PHY-HP sand filled baffles I am building, I got a pair of 12 inch full rangers.
Trial assembly and testing was disappointing with way too much bass response, even down into the mid 20hz region.
I have tamed them by reverting to a pair of old 8 inchers and raising the baffles off the floor a bit. Also, folding the wings back and fitting a bass trap has helped.
Have lost the very lowest notes of a pipe organ since they back off significantly below 35 hz.For any normal music, reggae, dub, electronica etc there is more and better bass than I have heard before. Fast, detailed, delicate and warm.
I can't understand what I did wrong to get this result. I think the NOS tubes I am using must take some responsibility along with the 80kg of sand I managed to squeeze in.
I should have been more skeptical of statements that OBs do not make good bass.
That is not always true.
  Reply With Quote
Old 7th November 2012, 07:39 PM   #10
aarvin2 is offline aarvin2  Mauritius
diyAudio Member
 
Join Date: Sep 2012
I think it depends on the Qts of your speaker no(higher Qts, more bass in a less tight way) ?? and a 12" moves a lot of air!!

On my case i'm dealing with 3-5" speakers and a Qts of lower than 0.3
  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
Open Baffle Bass kctess5 Multi-Way 21 10th February 2012 10:54 AM
amp for bass open baffle felixx Pass Labs 4 12th December 2006 07:59 PM
Which driver for open baffle bass??? loudandclear Subwoofers 2 18th December 2005 05:07 AM
Horn vs Open baffle bass paulspencer Multi-Way 192 2nd April 2005 12:08 PM


New To Site? Need Help?

All times are GMT. The time now is 03:16 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