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

[NWCgrad]

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.

[NWCgrad]

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!!!

[Etocynned]

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.

[bjorno]

Originally Posted by Etocynned

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

[bjorno]

[QUOTE=NWCgrad;3184563..When calculating the resulting response to the design, I only see minor changes. Are my changes correct or am I way off base..[/QUOTE]

Hi,

Agree,I will check closer within a few days.

b

[Etocynned]

Ya thx for the response b i was measuring based on the original. The last one is shorter and my trunk is actually 37" between the wheel wells.

regarding the freq response measurments, what was the power level for the 115db output?

[bjorno]

Originally Posted by Etocynned

Ya thx for the response b i was measuring based on the original. The last one is shorter and my trunk is actually 37" between the wheel wells.

regarding the freq response measurments, what was the power level for the 115db output?

I think it was 100W into 8ohm Rms in 1.0 x Pi

b

[NWCgrad]

Nd

Originally Posted by bjorno

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!

[NWCgrad]

Originally Posted by Etocynned

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, Lab12 - Tapped Horn -).

[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