1st BFM build: 2 X Omni 15 TallBoy in 2-12 configuration

[aeolos]

Greetings all,

Day 1

Made it to Suwanee Lumber to buy the plywood for the cabs: Baltic birch BBB 12 mm for the cabs themselves, and 18 mm for the cutting jig. Total cost for 3 5' by 5' sheets of 12 mm and 1 5' by 5' sheet of 18 mm, including Georgia state sales tax: $123.99 (USD). Was pleasantly surprised by this figure, expected it to be $180.00 or more.

Thanks one more time to bzb and Michael M for pointing me toward Suwanee Lumber. Great wood at very fair prices, and the most helpful yard crew I have ever met, bar none. As bzb pointed out, and as the build photos show, 5' by 5' sheets do not fit into an old Ford pickup truck with a top on the box. Given the load order (3 sheets of 12 mm on the bottom, with the 1 sheet of 18 mm on top), in my case 5 inches had to be taken off the 12 mm sheets, and 6 inches off the 18 mm sheet.

Had brought the battery-powered circular saw to make the required cuts that would allow the sheets to fit in the truck. What I failed to bring was batteries with sufficient charge to make those cuts. Was charging the battery off an inverter in the truck, making a cut and exhausting the barely-charged battery, charging again for a few minutes and cutting again, etc. etc. Was bogged down on the 18 mm sheet.

Well, comes quitting time and one of the guys looks at me and asks "is all you need that cut?", grabs the 18 mm sheet and trots off to their huge table saw, makes the cut, and runs back with it. Another guy went and got me a bottle of water (about 94 degrees F there this afternoon). I wholeheartedly recommend Suwanee Lumber if you are in the neighborhood and need high-quality lumber that you cannot get at any big box store. Great people.

Will add links to the build photos shortly: intend to thoroughly document this project to perhaps provide help to others who are considering building BFM cabs, and Omni 15 TallBoys in particular. Off to a good start.

best
--aeolos

[67baja]

I really love hearing stories that renew my faith in humanity! I recently went through some really bad sad family stuff and the ex-wife of my recently deceased brother (Marine vet) gave me hope that humanity isn't just money hungry back stabbing wastes. it is nice to hear of people helping people just cuz they can.

Build on!

[aeolos]

Hi 67baja,

There is certainly more than enough misery to go around, and I am sorry to hear that you got more than your ration. She is right though: the good people exist, and probably a lot more of them than is immediately obvious. The people of the lie do so much damage, out of all proportion to their number seemingly, that often it is hard to remember the good people.

Especially when you in the middle of the mulch, or are clawing your way out of it. Peace and strength to you.

best
--aeolos

[aeolos]

How come when the plywood went into the truck, it won't come out?

Doh. To get them to go in, as you see, took about a 5" cut off the side of each sheet. So it should come out just like it went in, yes?

Um, no.

Picture of the formerly 5' X 5' sheets of no-kidding Baltic birch plywood stuck in the truck:

[aeolos]

So, took another 12" by 6" triangle off the near left corner of each sheet, except for the bottom one which was 18 mm and DID come out, and away we go.

Here's the brand mark on the wood:

[aeolos]

2 questions, your help as always much appreciated:

1) Is 0.19 ohms a low enough DCR for the 1.1 mH inductor in the low-pass filter for the Omni 15 Tallboy in the 2-12 configuration? I've got a couple of 1.1 mH inductors wound from 12 gauge "99.99% pure" copper tape and polyester film on a hardwood bobbin (equivalent to air core) that have specs stating 0.19 ohm DCR and 650 watts RMS power handling capacity. Will they work OK? Big fat things, probably weigh a kilo apiece.

2) Is 3" thick convoluted polyurethane foam too thick to be used to line the cabinets? Found the foam here:

http://www.walmart.com/ip/La-Z-Boy-BigS ... r/22991618

Can of course slice some of the thickness away if need be.

Many thanks
--aeolos

[aeolos]

No time to post for a while. A fair amount of work done though. Made most of the mistakes that can be made I think, threw out some things and did them over.

To answer my own question: the plans give the minimum recommended resistance for the low pass inductor for the 2-12 version of the Omni 15, and yes, 0.19 ohms is low enough. Didn't see that because I ignored the subwoofer section of the plans. Doh.

You'll see a noob's version of Bill's panel jig in some of the photos below. Most highly recommended. Get the plan and build it carefully and use it, and you will be happy .

Construction begins (phone camera lens distortion, the angles are actually 90 degrees):

Cutting mid horn baffles; decided to do the horns out of order to see if I could build them

a 1/2" socket to run the RotoZip against gives the correct diameter for the phase plug; 2-pound hammer facilitates fine adjustments in socket position

partially built mid horn, sanding required; bonehead placement of hurricane nuts

extreme use of internal clamps, use what you got

more soon
--aeolos

[aeolos]

Build of 2 Omni 15 Tallboys continues

2 3/4" hole saw cuts near-perfect phase plug extension

Completed horns; filled the holes in the phase plugs with PL

attaching the front

Now don't shoot y'all, decided on Selenium 220Ti and HC23-25 instead of Eminence APT150; can fill in and switch back if necessary.
One of the pictures on Bill's site shows an older version of the Omni 15 with a Selenium HC23-25.
Here is a cabinet with 2 sides and a front, with horn cutouts

cutting the 2-12 baffle; using the circle-cutting guide that came with that old RotoZip

Doing all these steps twice of course. This is taking a while. Takes longer because I am learning as I go.

But it's fun, and I'm learning tons.

more soon
--aeolos

[88h88]

Seems to be going well!

[LelandCrooks]

Nice. I find the Omni's a particularly tricky cab for some reason.

[aeolos]

Thanks gentlemen. Leland, I am glad that somebody else finds this cabinet a little challenging. Of course anything would be a challenge to me, since before now my "woodworking skills" extended to assembling and finishing things bought at one of those "unfinished furniture" stores here in Atlanta.

What a neat material this Baltic birch plywood is. Found out that Krasny Yakor means Red Anchor in Russian, and that their US operation is called "Medallion Forest Products." There is another Krasny Yakor that makes marine chains and so on, but this plywood company is in Slobodskoy, in the Kirov region.

"A wooden Michael the Archangel Church built without a single nail in 1610 is the oldest surviving building in Slobodskoy and in the whole region."

http://www.visitkirov.ru/en/kirov-regio ... lobodskoy/

So they know something about woodworking in Slobodskoy. Puts me in mind of Al Capp somehow .

We all talk about globalization, but it still amazes me that a) a small lumberyard in Suwanee, Georgia USA routinely carries plywood from Slobodskoy, Kirov, Russia and that b) I can go look it up and find things out about it without even trying hard.

Good plywood it is too. Have the internal bracing in one of the cabs (photos coming soon), but not the flanges for the back panel yet, and the wood is so solid that the cabinet rings like a bell when struck (OK, not like a bell, but it does ring). Sounds like somewhere around 80-100 Hz poom. Hoping that the flanges will take at least some of that resonance out.

More shortly, this is great, and thanks again
--aeolos

[aeolos]

Onward: routing the 45 degree edge for the speaker side of the 2-12 baffle; the drill has a sanding drum on it, used to smooth that edge once cut

Business end of the router showing the 45 degree bit recessed to ensure no over-cutting

placing the 3012LF to mark for the hurricane nuts. At this point it fit nicely, but wait, I found a way to mess it up...

Do Not Do This: hammer hurricane nuts into the holes. You'll be sorreeee Abide By The Plan, draw the hurricane nuts tight with the driver in place... unless you enjoy modifying your driver to fit the hurricane nuts that are now in the wrong spots, because you hammered them in place... the durn things move.

dry fit: horns, top brace, and 2-12 driver baffle

More soon
--aeolos

[aeolos]

Now having gotten the hurricane nut placement wrong once, I found a new and improved way to get it wrong: used my little compass and straightedge to construct an octagon, that also did not work. Just use the driver...

another view of getting ready to install the top baffle brace

putting a top on

starting to look like a speaker cabinet, final dry fit before gluing mid horn, just about exactly as tall as the plans say it should be, perhaps 1/32" out at most

This is one of the two, both are now this far along, sanded semi-smooth externally (but the holes are not filled yet) and one has all the internal bracing in it. Only have the wherewithal to stuff one box just now but wait until you see them filters bubba, I have never seen coil nor cap to beat these.

Found it necessary to modify the two braces that extend from the top of the mid horn baffle to the top of the cab to accomodate the Selenium 220Ti driver, big heavy thing, and far back because of the HC23-25 horn. Fortunately a sanding drum on a drill can get the job done, more photos soon.

with sawdust in eyes, hair, and lungs, and PL on hands and clothes, I remain
--aeolos

[88h88]

with sawdust in eyes, hair, and lungs, and PL on hands and clothes, I remain
--aeolos

Get used to it...

[Chris_Allen]

Looking good.

I laugh every time you mention the mistakes that I've also made!