Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj

[NWCgrad]

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.

[NWCgrad]

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.

[bjorno]

Originally Posted by NWCgrad

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

[NWCgrad]

Originally Posted by bjorno

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

[m R g S r]

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?)

[bjorno]

Originally Posted by NWCgrad

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

[NWCgrad]

Originally Posted by m R g S r

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.

[NWCgrad]

Originally Posted by bjorno

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.

[bjorno]

Originally Posted by NWCgrad

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

[NWCgrad]

Originally Posted by bjorno

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.