Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - 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 15th July 2012, 07:30 AM   #1
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
Default Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj

Bjorno has designed a great T-TQWP for my Maelstrom X 18" subwoofer to cover from 13 to 50 Hz. I planned to rum 4 sealed Eminence LAB-12 boxes from 40 to 100 Hz.

However, today I started thinking about putting the LAB-12's in a T-TQWP or straight pipe enclosure. I would like to keep the enclosure under 36" tall so they are not taller than my main speakers (4 Pi speakers designed by Wayne Parham) on their stands.

Unfortunately my laptop with horn response software died recently, coupled with my ineptitude with the program, makes it impossible for me to try to develop a design. The driver is commonly used in tapped horn builds so it should be fine for this application. I only need the design to go down into the mid 30's and am willing to trade bottom end for size and upper bass impact.

Usage is about 80% music and 20% home theater.

I would greatly appreciate any assistance from the forum members.

Last edited by NWCgrad; 5th May 2013 at 02:05 AM.
  Reply With Quote
Old 15th July 2012, 09:20 AM   #2
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
I was looking through old posts yesterday, and I re-read justint's build thread (3015lf TH @ 35-40hz but only 20" deep help) . This straight-pipe build was 44" tall.

Seems like by substituting the LAB-12 driver an even smaller enclosure could be designed.

I am attaching info from justint's build and the Thiele & Small Parameters for the LAB-12.

Last edited by NWCgrad; 15th July 2012 at 09:23 AM.
  Reply With Quote
Old 15th July 2012, 09:45 AM   #3
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by NWCgrad View Post
I was looking through old posts yesterday, and I re-read justint's build thread (3015lf TH @ 35-40hz but only 20" deep help) . This straight-pipe build was 44" tall.

Seems like by substituting the LAB-12 driver an even smaller enclosure could be designed.

I am attaching info from justint's build and the Thiele & Small Parameters for the LAB-12.
Hi,

Submitting an OD-ML-TL that can be XO:d at 145Hz using a LR4 LPF (250 Hz= -20 dB down)= max Rec. frequency for to not fall into localization problems.

b
Attached Images
File Type: jpg LAB12_OD-ML-TL.JPG (238.4 KB, 2291 views)

Last edited by bjorno; 15th July 2012 at 09:50 AM.
  Reply With Quote
Old 15th July 2012, 10:51 AM   #4
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
Quote:
Originally Posted by bjorno View Post
Hi,

Submitting an OD-ML-TL that can be XO:d at 145Hz using a LR4 LPF (250 Hz= -20 dB down)= max Rec. frequency for to not fall into localization problems.

b
Bjorno,

What is an OD-ML-TL? The data looks perfect for what I want. I cannot believe it extends down to nearly 20 Hz flat. Wayne Parham (Pi speakers) recommended running flanking subs up to 120 Hz, seems like this would not a problem for this design.

Thanks once again for your assistance! I was really hoping you would weigh in.

Best Regards,
Steve
  Reply With Quote
Old 15th July 2012, 11:41 AM   #5
diyAudio Member
 
Join Date: Jan 2011
What is the size of the room this is going in? Are you going to distribute all these speakers? Or just run a wall of front speakers?

Seems like you'll have quite the low end with this setup. (13hz extension is a little excessive, unless it's pipe organ stuff?)
  Reply With Quote
Old 15th July 2012, 11:44 AM   #6
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by NWCgrad View Post
Bjorno,

What is an OD-ML-TL? The data looks perfect for what I want. I cannot believe it extends down to nearly 20 Hz flat. Wayne Parham (Pi speakers) recommended running flanking subs up to 120 Hz, seems like this would not a problem for this design.

Thanks once again for your assistance! I was really hoping you would weigh in.

Best Regards,
Steve
Hi Steve,

An OD-ML-TL is an Offset Driver M(a)(ss)*-Loaded Transmission-Line that you actually can build like an folded T-TQWT(T-QWP) but with the latter always necessary driver access lid removed(detached).
ML stands for a port-system that is loading a quarter-wave enclosure stuffed or not.

b

Last edited by bjorno; 15th July 2012 at 11:48 AM. Reason: * Stupid_You cannot write these letters in a row!
  Reply With Quote
Old 15th July 2012, 12:34 PM   #7
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
Quote:
Originally Posted by m R g S r View Post
What is the size of the room this is going in? Are you going to distribute all these speakers? Or just run a wall of front speakers?

Seems like you'll have quite the low end with this setup. (13hz extension is a little excessive, unless it's pipe organ stuff?)
The room is approximately 5000 cubic feet.

I plan to have 2 lab-12's just outside and behind my 4 Pi speakers (flanking subs crossed over at 120 Hz). The Maelstrom-X will be in a corner towards to front of the room (crossed over at 50 Hz, 4th order Butterworth). The remaining 2 lab-12's may go behind the listening position. Their location is flexible, so I will move and measure to minimize nulls.

Should be plenty of bass! I will use REW to set the subs so they are +3 dB.
  Reply With Quote
Old 15th July 2012, 12:38 PM   #8
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
Quote:
Originally Posted by bjorno View Post
Hi Steve,

An OD-ML-TL is an Offset Driver M(a)(ss)*-Loaded Transmission-Line that you actually can build like an folded T-TQWT(T-QWP) but with the latter always necessary driver access lid removed(detached).
ML stands for a port-system that is loading a quarter-wave enclosure stuffed or not.

b
Sounds interesting, I did a google search and did not really find info that allowed me to visualize your design. I am not very good at the design stage of speaker building, I enjoy the woodworking and final results.
  Reply With Quote
Old 15th July 2012, 03:01 PM   #9
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by NWCgrad View Post
Sounds interesting, I did a google search and did not really find info that allowed me to visualize your design. I am not very good at the design stage of speaker building, I enjoy the woodworking and final results.
In HR the CSA:s are labeled PAR= Parabolic CSA:s but when building an OD-ML-TL enclosure:Just flatten the CSA:s with the driver frame width, here= Divide the CSA:s with 31.34 cm used in the HR export function:

b
Attached Files
File Type: txt LAB12_OD-ML-TL.txt (18.6 KB, 178 views)
  Reply With Quote
Old 15th July 2012, 03:31 PM   #10
NWCgrad is offline NWCgrad  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Frederick, Maryland
Quote:
Originally Posted by bjorno View Post
In HR the CSA:s are labeled PAR= Parabolic CSA:s but when building an OD-ML-TL enclosure:Just flatten the CSA:s with the driver frame width, here= Divide the CSA:s with 31.34 cm used in the HR export function:

b
Bjorno, I am not sure what the information actually means. From the schematic diagram it appears the enclosure consists of 4 segments:

Segment 1: 50.479 liters
Driver Diaphram/Throat Chamber: 0.913 L
Segment 2: 55.712 L
Segment 4: 10.799 L

How do I calculate the enclosure from this infomation. From the schematic for the MAL-X I could somewhat see where the shape comes from, but with this design I am completely lost.

I was able to download hornresp on my new laptop, entered your values and played around for awhile - but I am way over my head.
  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
Chosing the taper in transmission lines, mass loaded or not Squeak Full Range 0 12th March 2011 11:02 AM
Slot loaded cube box for Lab-12 driver ashok Subwoofers 0 22nd March 2010 03:13 PM
Alpha Transmission line - can the driver be offset? adamt Multi-Way 3 26th June 2006 11:36 AM
Mass Loaded TL - Getting started? Dave Jones Multi-Way 4 12th April 2004 11:18 AM


New To Site? Need Help?

All times are GMT. The time now is 10:29 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