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

[Etocynned]

Originally Posted by NWCgrad

If you "need" greater dB output, you could replace the LAB-12 with a TC Sounds Epic 12 (NO change to the enclosure required). Would take more power before reaching Xmax, but will put out more dB's as shown in Hornresp attachment. Dang...Bjorno (and Tb46) designed on heck of an enclosure. I may supplement the two LAB-12 drivers I already own with two of the TC Sounds when I build the enclosures next summer.

I got the driver replacement idea from DrDyna on the LAB12-Tapped Horn thread (post #139, Lab12 - Tapped Horn -).

Ya actually 114 db at 20 hz 2 pi will become about 135 in car, and considering thats a 100 watt input, im more than happy.
Thx for the rework tho.

[von.ah]

This looks like a fantastic design. Awesome bandwidth for a sub, and not huge! If I was considering a sub build, this would be VERY high on the list...

[NWCgrad]

Originally Posted by Shadydave

NWCgrad,
I have been following this thread closely.
I have a pair of Lab 12's and I am waffling back and forth as to whether I want to build the Lab 12_OD_ML_TW or the long Lab 12 tapped horn.
Or one of each..
I drew the OD_ML_TL in Cadkey using the dims on your final drawing and it looks the same, plus I get the same Hrsp. inputs and results.
.
One thing that I have not figured out yet is what causes the impedance peak at 36 Hz.
This is where the efficiency goes up to almost 6% and the input power at 26 to 30 volts drops to only 6 Watts or so.
.
Also, do you have a HP filter value picked out?
.
My hats off to Bjorno and tb46 for this design.
.
I also can not figure out how you are compiling the long photo's and getting them to a hosting service. Let me try this one.
Anyway, good design. I await any comments about the port from Bjorno.
Dave

I will power subs with a Crown XTI 1002 amp, using the the built in DSP for HPF. I am thinking a second order BW at 20 Hz. Will supplement ULF with a very large T-TQWT also designed by Bjorno and tb46 (- 3 dB around 14 Hz).

I wish I could build now, my sealed 16" boxes with the LAB-12s has in room down to 35 Hz. These will be a significant improvement.

I make the attachments using Microsoft snip and paint.

Steve

[bjorno]

Hi NWCgrad, All

The outline of the suggested port system and the new position of the driver are IMO nearly spot on.

I've tested at least 5 damping schemes and a few different layouts of corner CSA: s / sections definitions.
Check out this MJK simulation I found best to represent your drawing: Look for eventual errors that are 'mistakenly' entered for the CSA: s and section lengths. I will test the impact of a suitable HPF and post the result later.

b

[DrDyna]

Originally Posted by NWCgrad

If you "need" greater dB output, you could replace the LAB-12 with a TC Sounds Epic 12 (NO change to the enclosure required). Would take more power before reaching Xmax, but will put out more dB's as shown in Hornresp attachment. Dang...Bjorno (and Tb46) designed on heck of an enclosure. I may supplement the two LAB-12 drivers I already own with two of the TC Sounds when I build the enclosures next summer.

I got the driver replacement idea from DrDyna on the LAB12-Tapped Horn thread (post #139, Lab12 - Tapped Horn -).

This looks like an awesome enclosure. I've been haunting this thread for a while just to see how it develops and I think I may try these at some point in the future as it only seems to require 1 sheet of material.

There's a 70's Cadillac in the driveway and I bet one of these would fit perfectly in the back of it!

[NWCgrad]

Originally Posted by DrDyna

This looks like an awesome enclosure. I've been haunting this thread for a while just to see how it develops and I think I may try these at some point in the future as it only seems to require 1 sheet of material.

There's a 70's Cadillac in the driveway and I bet one of these would fit perfectly in the back of it!

I bet it would sound great in a 70's Cadillac, all that heavy metal to provide pressure vessel gain...probably much better than my 2000's Accord.

I think Bjorno did a fantastic job on the design, and the fact that the TC Sounds driver models as well or better than the Lab 12 is a cool bonus.

I plan to build two this summer, probably with grade A plywood from a specialty wood store insteaad of home depot, amazingly the cost isn't as different as one would think. Two subs for two sheets of plywood seems pretty good.

[NWCgrad]

Originally Posted by bjorno

Hi NWCgrad, All

The outline of the suggested port system and the new position of the driver are IMO nearly spot on.

I've tested at least 5 damping schemes and a few different layouts of corner CSA: s / sections definitions.
Check out this MJK simulation I found best to represent your drawing: Look for eventual errors that are 'mistakenly' entered for the CSA: s and section lengths. I will test the impact of a suitable HPF and post the result later.

b

Bjorno, Glad to read that my moving the driver and changing the internal layout didn't mess up the design. I was very careful to keep the internal dimensions the same.

I am still going over your attachment, you sure can pack a lot of information into a single post.

[NWCgrad]

Originally Posted by bjorno

Hi NWCgrad, All

The outline of the suggested port system and the new position of the driver are IMO nearly spot on.

I've tested at least 5 damping schemes and a few different layouts of corner CSA: s / sections definitions.
Check out this MJK simulation I found best to represent your drawing: Look for eventual errors that are 'mistakenly' entered for the CSA: s and section lengths. I will test the impact of a suitable HPF and post the result later.

b

Bjorno,

I looked at the sections in the transmission line profile in your attachement. It looks like the version in the spreadsheet has a total length 7.91 inches longer that the drawing. I believe it is due to the additional volume showed in the profile due to each of the folds of the enclosure. Thus, I "think" there are no errors entered for the CSA's. All the secion lengths look correct to me, I lined up each length on the model and the drawing to compare and they seem to match pretty well.

Am I correct?

[Samuel Jayaraj]

Originally Posted by NWCgrad

Bjorno has designed a great T-TQWP for my Maelstrom X 18" subwoofer to cover from 13 to 50 Hz.

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.

Now that this sub is going down to 20Hz @ 114db, would you still use the Maelstrom X 18" sub?

How does this sub compare to Don's fold of a TH using LAB12 and a series inductor, which is ofcourse capable of 130db? Admit that it is much bigger, but that apart, in terms of sound quality for music and impact for HT?

[NWCgrad]

Originally Posted by Samuel Jayaraj

Now that this sub is going down to 20Hz @ 114db, would you still use the Maelstrom X 18" sub?

How does this sub compare to Don's fold of a TH using LAB12 and a series inductor, which is ofcourse capable of 130db? Admit that it is much bigger, but that apart, in terms of sound quality for music and impact for HT?

That is a good question, I have no experience with ultralow bass as I have used my Maelstrom X in a sealed enclosure in a large open space (measured flat in room down to the mid 20's). Based on the design parameters, the new Mal-X enclosure should provide strong output at 13 Hz (- 3 dB based on Hornresp).

I will build two of the Lab12's in a few months and see if I am satisfied. My current setup in Cambodia (two year assignment) only goes down to 30 Hz. The current setup is two Lab 12's in sealed 16" cubes and an old Paradigm PDR 12. With them being flat to 20 Hz, the Mal-X may be more trouble than it is worth to integrate. I cannot say how important the range from 12 to 20 Hz is for movies, I do not think it at all important for music. For music I "think" I would only run the Lab 12's.

I have not modeled Don's tapped horn, I thought about building one but it is larger than I wanted. I know it will play significantly louder and I defer to others who have heard examples of each enclusure type (OD-ML-TL vice TH) to offer opinions on sound quality differences.