BIB's, what did I do wrong? - 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 16th December 2006, 01:56 PM   #1
diyAudio Member
 
Rick J. B.'s Avatar
 
Join Date: Dec 2006
Question BIB's, what did I do wrong?

Hello,

My first post, great set of forums.

About 4 years ago I built a pair of BIB enclosures for my Lowther DX-3's.

I must have done something wrong because the bass response in almost non existent.

I know little of speaker design so I probably screwed up the dimensions.

Click the image to open in full size.

Mine are 86" tall, 11" wide & 14" deep. These are the OD
dimensions.

Click the image to open in full size.

Z Driver dimension is 43.00" (top of cabinet to center of driver)

L - line length = 6.62" for A, B, & C.

Sm (terminus area) = 135.81"

Click the image to open in full size.

So where did I screw up?

Thanks for any and all replies.

Rick
  Reply With Quote
Old 16th December 2006, 02:15 PM   #2
diyAudio Member
 
Join Date: Aug 2004
Location: Buenos Aires
Send a message via Yahoo to JORGETronic
Hi,
I am not an expert, but if you check the design that GM has done for the DX3 you are a litle far from the suggested dims..

Dims suggested for your driver are:
L=120"
Zdriver=25.2" from closed end
Sm= 220in2

And you have:
L=86"(tall)x 2= 172"...seems too long
Z= dont see that in your post, but seems to be larger that recommended

Sm= 11" wide x 14" deep =154, too small compared with the suggested 220..

Iwuld try the suggested Dims by GM with some cheap wood, then you can choose..
Hope this heps!!
__________________
Jorge
  Reply With Quote
Old 16th December 2006, 03:02 PM   #3
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Hi Rick

First up, many congratulations on the quality of your construction. Looks great.

OK, Lowther DX3. Well, contrary to Lowther's claims, Fs is actually up in the high 50Hz regions (Martin's measured around 60Hz for his drivers), not the claimed 36Hz. FWIW, my suspicion is that a lot of Lowther owners are unhappy because their cabinets have been designed to the factory specifications, and the resultant mis-match is the reason they're getting duff sound.

Greg's done a couple of BIB designs for Lowthers, as have I, as suggested above.

So, what's gone wrong? Well, as noted, currently, line length is too great. You've accidentally tuned far too low, which has the result that the midbass and under goes walkabout. Zdriver seems to be out as well. You have roughly 172in line length here. Ideally, Zdriver for that length wants to be 37.5in (37.324 actually, but let's not split hairs ) Let's see what we can do as an alternative.

Greg's works, that's for sure. As an alternative, so will this (driver specs from Martin King's accurate measurements):

Line length = 128in
Zdriver = 27.75in
Sl = 126in^2.

Ideally WxD dimensions want to be in proportion of 1:1.4142, or rounded to the nearest sensible figure. Graph shows 1/2 space response, no stuffing assumed. Corner loaded, should be ~flat to 30Hz, and much smoothed out thanks to the room boosting the resistive portion of the acoustic impedence and increasing the effective size of the mouth by a factor of 8. Stuff the point above the driver lightly, and place an inch or so of damping material on the base of the cabinet.

Why the big difference in mouth area between GM's and mine? Different approach -all the BIB simulations on the zillaspeak pages Jeff so kindly hosts were done by Greg or myself, but we have subtly different takes on the subject. Greg favours a larger mouth than I do, and bringing the response flat with some series resistance, while I will often tend to go for a smaller terminus, and usually a fractionally longer line without the resistance. End result is usually a happy builder in both cases, so up to you really!

Good luck & let us know if we can help
Scott
Attached Images
File Type: gif dx3 bib.gif (6.5 KB, 631 views)
__________________
Community site www.frugal-horn.com Commercial site www.wodendesign.com
  Reply With Quote
Old 16th December 2006, 03:03 PM   #4
gychang is offline gychang  United States
diyAudio Member
 
Join Date: Feb 2005
Location: Davis, California
Default Re: BIB's, what did I do wrong?

Quote:
Originally posted by Rick J. B.
Hello,

About 4 years ago I built a pair of BIB enclosures for my Lowther DX-3's.

I must have done something wrong because the bass response in almost non existent.

So where did I screw up?

Thanks for any and all replies.

Rick

I built 2 BIBs with different speakers and both sets are excellent in the base. I agree there is a mistake, speakers look great, and hope u get to use the proper dimensions and not give up on BIB...

http://www.zillaspeak.com/bib-lowther.asp

gychang
  Reply With Quote
Old 16th December 2006, 05:12 PM   #5
diyAudio Member
 
Rick J. B.'s Avatar
 
Join Date: Dec 2006
Default Do these dimensions look right?

I sketched this quick so pardon the poor drafting.

Do these dimensions look right for my DX-3's?

Click the image to open in full size.
  Reply With Quote
Old 16th December 2006, 05:25 PM   #6
djQUAN is offline djQUAN  Philippines
diyAudio Member
 
Join Date: May 2004
Location: manila
Send a message via MSN to djQUAN Send a message via Yahoo to djQUAN
or you could have wired the speakers in opposite polarity.
  Reply With Quote
Old 16th December 2006, 05:52 PM   #7
BHD is offline BHD  United States
diyAudio Member
 
BHD's Avatar
 
Join Date: Jun 2004
Location: Brooklyn Park, MN
Send a message via Yahoo to BHD
Those cabinets are gorgeous. It's a shame the lowthers don't work in them. I'd say try to find a driver (Fostex?) that will fit the dimensions of your current cabinet.

__________________
My religion is the golden rule. The only time it's forsaken me is when I've forsaken it first.
  Reply With Quote
Old 16th December 2006, 06:24 PM   #8
diyAudio Member
 
Rick J. B.'s Avatar
 
Join Date: Dec 2006
Surely I couldn't have wired both wrong?

No I was very careful not to do just that. Since I soldered all connections I double and triple checked everything.
  Reply With Quote
Old 16th December 2006, 07:03 PM   #9
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Should do the job nicely. Remember to calculate the thickness of the internal baffle when cutting -it's easy to forget! So, assuming 3/4in material, your cabinet should be, externally, 64.75in tall (including a base), 10.5in wide, and 16.25in deep.

Use a fairly high resistance speaker cable if possible, which should also help keep the LF up a bit: magnet wire is ideal for this purpose, or a pair of 24AWG conductors extracted from a run of Cat5. Make sure that there's some damping material on the front of the internal baffle directly behind the driver as well. A piece of felt for example. That should help prevent reflections back through the cone.

Drop a pair of Fostex FE206E in your existing cabinets BTW & either keep them for parties, or sell them on. Bass should not be lacking.

Best
Scott
__________________
Community site www.frugal-horn.com Commercial site www.wodendesign.com
  Reply With Quote
Old 16th December 2006, 07:33 PM   #10
diyAudio Member
 
Rick J. B.'s Avatar
 
Join Date: Dec 2006
Thanks Scott.

So the Fostex FE206E will work in the dimensions of my current enclosures? Man if that's the case I could put them in and sell them to finance the next set of cabinets!

Of course I'd have to sell them to someone close. These mothers are huge & heavy.

Rick
  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
Wrong Voltage / current on BoZ... or Wrong Measuring ? gionag Pass Labs 8 14th May 2008 11:24 AM
what's wrong with it? bravesz Digital Source 6 27th September 2006 08:15 AM
something wrong? spyder6 Subwoofers 2 21st February 2005 06:58 PM


New To Site? Need Help?

All times are GMT. The time now is 09:20 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