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bkeane1259
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Docere MLTL - build thread

Sat May 10, 2014 5:54 pm

I'm doing Jim Griffin's MLTL of Jeff Bagby's Docere. The Docere was the system that Jeff designed and then used in his speaker workshop last December. Pics from the workshop can be seen here - http://tinyurl.com/kyfbrm2.

The bookshelf version (the original Jeff B design) is offered as a kit here at Meniscus - http://meniscusaudio.com/docero-full-pair-p-1408.html

Jim Griffin is a MLTL design master and the Docere MLTL should add some significant low end to an already great woofer, the Meniscus Eclipse W6520R-4.

Just got started on these this weekend so there's not much progress thus far. The plan is to do a 1.25" constrained layer baffle with 0.75" ply and 0.5" MDF sandwiched together with Acry-Tech Acoust-X. http://tinyurl.com/kq58s83

Some initial pics-

The original design:
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The MLTL:
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In boxycad:
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Coating the ply with Acoust-X:

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Fabricating lots of bracing in my super duper fancy brace fabrication rig:
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Only half done with the braces so far and about to run out to watch the White Sox kick some booty. More later:
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Last edited by bkeane1259 on Tue May 20, 2014 11:06 am, edited 1 time in total.
Bryan K.
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bkeane1259
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Re: Docere MLTL - build thread

Sat May 10, 2014 11:06 pm

Here's a short video on the Acoust-X application - https://www.youtube.com/watch?v=af8LHIldVXg
Bryan K.
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jrhollander
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Re: Docere MLTL - build thread

Sun May 11, 2014 10:12 am

So Bryan what the process for the constrained layer? Let dry and glue together, assemble wet? What I've read so far seems to indicated there needs to be a bond between layers?
 
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bkeane1259
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Re: Docere MLTL - build thread

Sun May 11, 2014 3:04 pm

I've never used Acoust-X before so the baffle will be a bit experimental. The product isn't a great bonding agent, so I'm going to be using a lot of screws. I thought about screwing the panels together while the Acoust-X was wet, but I didn't want to get a bunch of squeeze-out. So this is what I'm trying. I coated the ply and I’m letting that dry. Then I will coat the MDF panel and screw it onto the ply and let the whole baffle dry. This way I should (hopefully) get a good even layer of damping compound in between the ply and the MDF.
Bryan K.
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bkeane1259
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Re: Docere MLTL - build thread

Tue May 13, 2014 2:57 pm

Second set of brace holes cut (slightly smaller hole saw). Cutouts rounded over and all of them sanded. Fingers hurt. I need a sanding sponge for the cutouts.

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Here I'm coating the 1/2" MDF panels with Acoust-X. Right after coating, I'm screwing these on to the 3/4" ply which already has a layer of dried damping compound.

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Lots. Of. Screws. 67 to be exact in each baffle. Honestly I have no freaking clue if this is going to make a beneficial difference but it's fun to experiment.

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A closeup of some minimal squeeze-out. I expected this but my intention with doing one panel dry and one wet was to fill all the textured grooves and ridges created by the roller in the Acoust-X application on the ply panels. Now I'm sure there's a "complete layer" of damping compound in between the ply and MDF. Again, no clue if this is adding any real value to the cabinet. We'll see though.

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Starting to rain again, so that's all for today.
Bryan K.
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mattsk8
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Re: Docere MLTL - build thread

Tue May 13, 2014 3:08 pm

Can't wait to hear these in Indiana!! 8-)
 
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bkeane1259
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Re: Docere MLTL - build thread

Tue May 13, 2014 6:32 pm

Here's a good link to a variety of volume calculators.

http://www.hometheatershack.com/forums/ ... #undefined

Considering that I'm going to use five 3/4" thick window braces per cabinet I did the calculations to see how much I'd have to alter the depth of the cabinet to maintain the 1.4 ft^3 internal volume. Sure enough, mine will be an extra 1/2" deeper to maintain the proper volume.

In the OP, I posted the Boxycad sheet for the original design. My cabinets will end up being 10.5” deep – An extra ½” for brace volume displacement and an extra ½” for the constrained front baffle.
Bryan K.
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bkeane1259
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Re: Docere MLTL - build thread

Wed May 14, 2014 3:20 pm

The rest of the panels are cut, glued, clamped and slightly out of square as usual, but I seem to get a little better with each build. This one is pretty close. :roll:

Dry-fitting the cabinets together looked promising........but..... I think part of the problem is I do not have any sort of protocol for gluing and clamping towers. I've absolutely required help from my 19-yr-old any time I've done a large cabinet and this one is no different. Seems as soon as you start spreading the glue and clamping stuff, inevitably a panel is going to shift. Well, this is my experience anyway.

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Did I mention that I need more clamps? I do...no joke.

One tower:

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The other tower. Notice that in this cabinet, I tossed in a few pieces of scrap to help align things. I did not dado the braces in this build and that definitely made gluing and clamping more challenging.

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The bracing is randomly spaced and the circle cutouts alternate. Does it help break up standing waves? I have heard it does but I've never seen any scientific proof. Of note: One brace will sit between the tweet/woof and one brace was purposely positioned below the woofer to mark the end of the line stuffing. This way I can just stack the required amount of stuffing for the MLTL between the braces, up to the top of the cabinet. BTW - Meniscus sells the perfect product for this. The MLTL calls for stuffing with uniform density of 0.75 lb/ft^3 and their bonded dacron just needs to be cut into sheets that fit the line without compression. How easy is that?

Bonded Dacron - http://meniscusaudio.com/bonded-dacron-p-185.html

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These are sitting in the garage curing. Tomorrow I have a lot of sanding to do, or maybe it will just be Duratex to the rescue. Have not decided on a specific finish yet, other than the baffle which will definitely be black Duratex.
Bryan K.
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bkeane1259
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Re: Docere MLTL - build thread

Thu May 15, 2014 5:52 pm

Took some time today in between rain storms to unclamp and sand the cabinets. First order of business is to knock down some of the glue squeezeout and high spots with the router and flush trim bit. A while back I picked up a big honkin dual bearing flush/pattern bit from MLCS - http://tinyurl.com/mxy9ltg I think it was $25 at the time but it was well worth the $$ - one of my favorite bits.

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After flush trimming - just need to sand away minimal glue now.

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Some 80-grit sanding to get the butt-joints perfectly level.

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Right on cue.....Mother Nature steps in to ruin the party with yet more rain. :x Most of the sanding is done....still need to do some prep work before painting/veneering.

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My thought right now is to veneer the sides and do black Duratex front, back, top, bottom. However, I'm not 100% sold on that idea. Not even sure if I have enough veneer, which is still in storage with a bunch of other stuff from our move last year. Sadly my tools and hobby stuff remains in a state of chaos as I never got around to organizing everything. Somebody sign me up for "Mission Organization" please. :lol:
Bryan K.
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bkeane1259
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Re: Docere MLTL - build thread

Fri May 16, 2014 5:02 pm

May 16 - Pissing down rain and 40 degrees in Chicago. :evil:
Bryan K.
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