Open baffle bass behaviour - 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 28th December 2006, 08:29 PM   #1
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Default Open baffle bass behaviour

Hello!

Are there any general (and corroborated!) rules that show the way to acceptable bass-behaviour from an open baffle? I just played a little with a 30-20cm oval console driver (light paper cone - alnico magnets - high Qts - accordion surround - very low Xmax) in a 1,2 * 1 meter cabinet.

First with the driver mounted very close to the ground: there was a large peak in the bass that messed things up (like the effect of the bass-boost on my girlfriend's Sony)

... then I turned the baffle 90 so that the driver was half-way up in height and to the extreme left (or right for that matter): bass peak was gone but now the bass got very slow.

The aim would be reasonably flat bass-output untill around 100-150hz, where a pair of subwoofers could fill-in. Not simply 'bigger is better is more low-end' when that low-end isn't worth much.

Thanks (and more questions to come about this subject)

Simon
  Reply With Quote
Old 28th December 2006, 09:03 PM   #2
diyAudio Member
 
Join Date: Jun 2004
Location: Warsaw
-> Klimon

Maybe you can find something interesting on audiocircle forum
http://www.audiocircle.com/circles/index.php?board=90.0
  Reply With Quote
Old 28th December 2006, 09:05 PM   #3
Geoff H is offline Geoff H  Australia
diyAudio Member
 
Join Date: Oct 2006
Hi Simon, this has been covered in other posts. Basically, keep the driver away from the floor to preserve mids. Wings can be added to increase the width of the baffle, and also provide support, and a shelf above the driver to extend the minimum front to back distance.

Regards,
Geoff.
  Reply With Quote
Old 28th December 2006, 10:56 PM   #4
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Buble_corp: thanks for that link!! Took a quick look and it's a whole vault of OB info I wasn't aware of - more reading to do in the coming days...

Geoff: Thanks for the quick reply - I've been reading alot about OB and the placement (floor/ ear-level) seems to be disputed; e.g. the JE-labs or almost any design with helper woofer puts the low (or only) driver close to the floor. When simulating using 'the edge' the benefit of close-floor mounting is evident (apart from the lower f3 there is less floor-bounce). I'll have to experiment some more to find the best solution using only one driver. Going from near-floor to ear level with these really didn't make a difference regarding midrange, only bass changed (from peaky to slow )

A few other questions that are even more relevant as I'm planning to build the final versions of two OB line arrays and wouldn't want the same dubious results after all that work; basically my question is if the bass will get slow or 'peaky' (in the audible range) when adding more baffle, the fact that these are line arrays (much more Sd) might change things:

-- First line array uses eight 4" woofers pro side; seventies paper cone, high Qts, low xmax (accordian surrounds)... I've been playing these with smallest possible baffle (just one narrow line to hold the drivers) and the bass-quality is good. In the final version I was planning to add baffle to get more extension, in the form of wings (110-140 degrees vs. front baffle) + bottom + lid (like a box with sloped sides and without a back), basically to extend the bass. Will there be great danger to mess up the bass by doing this, e.g. making it slow / getting annoying peaks?

-- Second line array uses six 8" midwoofers, high Qts, foam surrounds and higher xmax; Same 'cabinet' plan as for the previous array; different variables here are the even higher overall Sd and Xmax; same question: in how far is such a line array prone to reduced bass quality when adding baffle?

Thanks --- Sorry for the long post // no easy questions I'm sure but any advice is welcome!!

Simon
  Reply With Quote
Old 29th December 2006, 05:57 AM   #5
Geoff H is offline Geoff H  Australia
diyAudio Member
 
Join Date: Oct 2006
Simon, are you adventurous? Given the drivers you have, I would place the 4 of the 8" in to a bass dipole (H shaped, with top and base) and the 8 4" on a line array baffle, optimised for about 130 Hz.

Aim for a crossover of 150 Hz. If that combo works, a line array of ribbons above 1/2 the frq limit of the 4" array.

I haven't heard a base dipole yet, but they seem interesting. I can't find the links, I thought I saved them.

BTW, I have dropped my xo down to 100 Hz. It's not going back. Better on sax, tuba, acoustic guitar, (esp 12 string) violin, voice, applause, and percussion. And it's not bi-amped yet.

Regards,
Geoff.

Afterthought: 3 or 4 bass dipoles with 2 8" in each, in a line array across the floor.
  Reply With Quote
Old 29th December 2006, 07:05 AM   #6
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Geoff, all ways end up in Rome (or how does one translate that??) -

My first plan was to do something similar (following a tip from johnincr: manifold with the woofers mounted push-pull) but there are several minussen:

-- efficiency of the 8" woofer ensemble would be lower than the 4" line array (unless I biamp which isn't for the very near future)

-- the woofers are very useable in the midrange, with a relatively smooth roll-off

Now I gather with some extra baffle I'll be able to reach 100hz with both arrays and a pair of subs will suffice.

I like the ribbon line array idea but that's a long shot from my budget - the mentioned woofers cost me 2$ apiece Too much plans at the same time have left me with no money (and a lot of parts )

When thinking things over I don't expect much deterioration in bass-quality with the winged line arrays, whole different story than single-driver - atleast in my head.

Cheers,

Simon
  Reply With Quote
Old 29th December 2006, 07:34 AM   #7
diyAudio Moderator Emeritus
 
roddyama's Avatar
 
Join Date: Jan 2002
Location: Michigan
Hi Simon,

Take a look at this thread , in particular the open baffle speakers by Peter Daniels. I have since heard these speakers and there is no shortage of clean solid bass.
__________________
Rodd Yamashita
  Reply With Quote
Old 29th December 2006, 12:06 PM   #8
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
thanks Rodd - the reason why that one goes so deep is probably the high Sd(2 15inchers/ speaker) --- My line arrays will be also benefitting from that; curious what they'll do with the little wings.

Simon
  Reply With Quote
Old 29th December 2006, 12:56 PM   #9
Geoff H is offline Geoff H  Australia
diyAudio Member
 
Join Date: Oct 2006
Hi Simon,

Did you see this thread? U-Baffle

It has links to the sites I was referring to.

Geoff
  Reply With Quote
Old 29th December 2006, 03:10 PM   #10
Dumbass is offline Dumbass  British Antarctic Territory
diyAudio Member
 
Join Date: Mar 2003
Location: British Antarctic Territory
Get yourself well-acquainted with this web page:
http://linkwitzlab.com/models.htm

And regarding the frequency-dependence of boundary reinforcement, check out this draft of a whitepaper I started last year. It's not perfect, but it shows why boundary reinforcement is different for different frequencies:
http://www.stat.ucla.edu/~erickson/tmp/boundary.pdf
  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-dipole-what amp felixx Multi-Way 20 13th December 2006 06:53 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 09:47 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