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Discussion Starter #1 (Edited)
I believe I bought the last LMS Ultra 5400 18” and recently finished a 4 cubic foot sealed design. Not knowing if and when LMS Ultra’s will be available again I decided to pick up a pair of LMS-R 15” drivers and build 3 cubic foot sealed enclosures. I might add a second 18" if they become available again.

My room is going to make it difficult to place the subs but I have a few places I hope I can put them.

The LMS-R 15" drivers have arrived and the build is underway.

LMS Ultra 5400 18" - 4 cubic foot sealed enclosure



2 ea. LMS-R 15" - 3 cubic foot sealed enclosures

 

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Wonderful build - I currently have 2 LMS-U 18's and 4 LMS-R 15's all sealed in the same box sizes of your build. You will not be disappointed with the quality of bass, that is for sure. Hope the placement works out!

:D

Before you put the 15's in your boxes be sure to free air test them, getting the cones moving. My last two were both glued improperly and required some fixing/returning. I've read of a couple others that did the same. You'll know by the ugly rubbing/flapping noise within a minute or two of testing. I found it easier to hear the issue with actual music vs a sine wave.
 

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Discussion Starter #7
BassThatHz, I can hear your subs on the west side of the Cascades.

Djoel, GizzeGutten, Scott and Cubalis2, thanks for the kind words.

The LMS-R 15” boxes are assembled and ready for the finish work to begin. Clamps are on box 1 gluing the ¼ inch oak plywood I use on the back of the subs.
 

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Discussion Starter #8 (Edited)
Wonderful build - I currently have 2 LMS-U 18's and 4 LMS-R 15's all sealed in the same box sizes of your build. You will not be disappointed with the quality of bass, that is for sure. Hope the placement works out!

:D

Before you put the 15's in your boxes be sure to free air test them, getting the cones moving. My last two were both glued improperly and required some fixing/returning. I've read of a couple others that did the same. You'll know by the ugly rubbing/flapping noise within a minute or two of testing. I found it easier to hear the issue with actual music vs a sine wave.
Thanks for the suggestion. I have only opened one of the boxes to test the fit of my through cut and did notice the coils looked different then the LMS Ultra but assume that is the intended design. Hopefully I don't have the problem.
 

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Thanks for the suggestion. I have only opened one of the boxes to test the fit of my through cut and did notice the coils looked different then the LMS Ultra but assume that is the intended design. Hopefully I don't have the problem.
They do have different looking coils, so no worries there.

I just wanted you to not have to go through the annoyance of finishing a (beautiful!) box, mounting the driver(s), firing it up and having to take it out again. It's remarkably easy to slip pulling 40lb+ 15" drivers out of awkwardly tight spaces, which inevitably leads to some kind of box damage... first hand experience talking ;) minus the beautiful box part.

Look forward to seeing all three finished.
 

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Discussion Starter #12
A slow process but the back 1/4" oak plywood is on both boxes and I've glued and edge trimmed the first side with 1/2" x 4" solid oak.

One of the LMS-R 15: enclosures with the first side of 1/2" x 4" glued and sprinkled with some Seattle rain

 

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Discussion Starter #14
Is that veneer over a roundover in the top pic? Or is the front baffle solid oak or other real wood?
I am not using veneer. The fascia is made from 2" x 4" solid Oak glued together before routing the countersink and through cut and then gluing to the front of the cabinet.

The sides are 1/2" x 4 " solid oak boards and the back is 1/4" oak plywood. This allows me to use a 1 1/2 inch round-over on the fascia and 1/2 inch round-over on the sides. This is of course put on the assembled enclosure. While it is added for cosmetics, it does add strength while covering and sealing all the MDF seams.
 
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Discussion Starter #16
Nice. Have you weighed that puppy?

I could only guess. I was barely able to carry the 4 cubic foot box from my garage to the top of the basement stairs and let it slowly slide down the carpeted stairs once I got it there. Now that it has the 86+ pound driver installed there is no way I could lift it by myself and shouldn't have tried it without the driver.

The 3 cubic foot LMS-R 15” boxes are still very heavy but are manageable so far.
 

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What does it sound like when you knock on that 4cuf box? Like knocking on concrete?

Do you use different woods to make it more sturdy and move the natural resonances up or what was your reasoning for that, please?
 

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Discussion Starter #18 (Edited)
What does it sound like when you knock on that 4cuf box? Like knocking on concrete?

Do you use different woods to make it more sturdy and move the natural resonances up or what was your reasoning for that, please?

The enclosures are dead solid.

I attempt to follow basic guidelines recommended in the North Creek Cabinet Handbook. (Copyright Credit to George Short). The basic box is made out of MDF and Baltic Birch Plywood and is likely sufficient without adding additional layers.

I add the Oak primarily for cosmetics but it certainly adds rigidity as well.

MDF and BB have different densities and damping characteristics. MDF is very dense while BB is at least 4 times as stiff as MDF. BB adds stiffness to the bracing and front and back of the enclosure and MDF adds density to all 6 sides. The front and back is a composite panel made of a layer of ¾” MDF laminated to a layer of ¾: BB.


The resonances of the two layers are different and George explains the design advantages and I could only repeat what is explained in the book since the science is beyond me. Some of the design characteristics are more applicable to a full range speaker than a sub-woofer.

There are also recommendations for brace spacing and spacers and cross braces that create a matrixed pattern of “I beams” that adds additional rigidity. The hard wood I add for a cabinet finish just adds to the mass of the enclosure, especially the fascia where the through cut for the driver weakens the front panel.


LMS-R 15" fascia clamped and drying before sanding, routing through cut and countersink and then gluing to cabinet front.



LMS-R 15" with sides and back completed. Waiting for hard wood fascia before sanding, rounding edges, staining and finishing.

 

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Thanks a bunch for your help. :) The book seems very interesting but couldn't find it on Amazon. Will dig further as a basis for research on future projects.

The build quality and thinking behind your enclosures is impressing to say the least, and the result of these will be sonic bliss I'm sure. Good for you I didn't get that last LMSU before you, because I eyed it hard when it popped up on PE, haha.
 

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Discussion Starter #20 (Edited)
The first of the two LMS-R 15" enclosures ready for sanding, staining and finishing.

 

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