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

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Final Plans

I have completed the final plans for the suboofer (attached). I made a 1:10 scale representation in powerpoint to calculate the exact dimensions of the materials used in the port and used the sizes of the boxes that made up the partitions for the actual size. Hopefully it will be close enough!

When I start to build the enclosures next summer I will first cut the two sides of the enclosure and make a drawing on the cut sides to verify all calculated measurements. I was able to fit the enclosure on one 4x8 standard sheet of plywood. Plan is to use US-made Red Oak A-1 domestic grade plywood (Plywood at Hardwoods Inc, Exotic & Domestic Lumber in Frederick).

From Bjorno's documentation it looks like I will need 1.066 lbs of stuffing.

Thanks to all who assisted or provided feedback.
 

Attachments

  • B-T-N LAB-12 OD-ML-TL FINAL_F3 = 21Hz.jpg
    B-T-N LAB-12 OD-ML-TL FINAL_F3 = 21Hz.jpg
    140.5 KB · Views: 1,106
  • B-T-N LAB-12 OD-ML-TL Detailed w cutsheet.pdf
    81.4 KB · Views: 236
Last edited:
Did I calcluate Hornresp correctly???

I am trying to figure out Hornresp (still, it seems I forget info as soon as I leran it). Looking at the original Hornresp input from Bjorno and the final drawings by tb46 there seems to be some minor changes, especially with the modified port system developed by Bjorno.

With the folding and dimenstions provided by tb46 that I modified the folding but not volume or length of L12 or L23, it seems the inputs are a little different.

So, the original S1, S2 and S3 was 513, but from the schematic drawing I calculate it to be 511.82 (horn width [16.3 cm] x internal cabinet width [31.4 cm]).

With the new port system, I do not have them at 169.00, I now calculate 169.56 (5.4 cm x 31.4 cm]. Due to the complexity of the port, I calculate horn segment 3 to be 12.25 vice 0.10 and horn segment 4 to be 57.20 vice 63.90.

When calculating the resulting response to the design, I only see minor changes. Are my changes correct or am I way off base. I keep going over the design because I cannot start to build until I return home to US (summer 2013)

Thanks for looking and for all the previous assistance!!!
 

Attachments

  • Final LAB 12 Design - Double Front Baffle.jpg
    Final LAB 12 Design - Double Front Baffle.jpg
    116.6 KB · Views: 965
  • Bjorno Original Hornresp Input vs tb46 Final Hornrep Input.jpg
    Bjorno Original Hornresp Input vs tb46 Final Hornrep Input.jpg
    422.1 KB · Views: 937
Hey this box would fit in my car if the 37" dimension was 36", is there anything i can do about that?

How can i do this?

edit: forget i asked. Remeasured the trunk.

psst will this play nice in my trunk?

guessing it will.

Hi Etocynned,

Why not just shave off an inch from the height, this volume loss would only imply at most a slight shift in the 3/4-wave supression, just add a little more stuffing in the 'Stub' or if you are picky, I wouldn't.

b :)
 
Nd
I think it was 100W into 8ohm Rms in 1.0 x Pi

b:)

Bjorno you have an excellent memory!

In a my home theater the individual units will be about 2 M from each other, is this close enough to get the 5 dB gain?

Later I may build two more. I plan to stack two together (bottom cabinet port up, top cabinet port down) and I assume this will add about 10 dB from the modeled response for one (125 dB), which will be more than enough headroom for my requirements.

Thanks again to Bjorno for his inspiration, creativity, and willingness to share his knowledge!
 
Hey this box would fit in my car if the 37" dimension was 36", is there anything i can do about that?

How can i do this?

edit: forget i asked. Remeasured the trunk.

psst will this play nice in my trunk?

guessing it will.

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, http://www.diyaudio.com/forums/subwoofers/143714-lab12-tapped-horn-14.html).
 

Attachments

  • LAB-12 vs Epic 12.jpg
    LAB-12 vs Epic 12.jpg
    159.9 KB · Views: 788
Last edited:
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..:D
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

lab12OD_ML_TL.jpg
 
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, http://www.diyaudio.com/forums/subwoofers/143714-lab12-tapped-horn-14.html).

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.
 
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..:D
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

lab12OD_ML_TL.jpg

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
 
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' :eek: entered for the CSA: s and section lengths. I will test the impact of a suitable HPF and post the result later.

b:)
 

Attachments

  • LAB12 ~108Wmax_OD_ML-TL.JPG
    LAB12 ~108Wmax_OD_ML-TL.JPG
    721.7 KB · Views: 898
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, http://www.diyaudio.com/forums/subwoofers/143714-lab12-tapped-horn-14.html).

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!
 
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.
 
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' :eek: 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.
 
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' :eek: 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?
 

Attachments

  • Bjorno's MLK Analysis for Density of Stuffing.jpg
    Bjorno's MLK Analysis for Density of Stuffing.jpg
    129.2 KB · Views: 812
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?
 
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.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.