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

[Bruce Weldy]

Wait until Bruce sees this picture. You have taken my OCD King title away from me,

Not even close......

[escapemcp]

OCD you see, as miked pointed out. As for filling the holes in the braces, well, there were the holes, and there I was, and the goo was close to hand, so... why not? I didn't like the imprecision of the screw placement and thought filling the holes might help, and it did, a little bit, to my eye anyway.

Maybe not King OCD, but no-one is ever going to see them FFS!!

Mr. OCD MBE perhaps?

[aeolos]

Bruce, you are quite right, and if you saw my so-called shop, you'd know how right you are. Disorderly.

escapemcp, you're right, nobody will see them... but me... in random thoughts... in the darkness of night... waiting for the traffic signal to change... unfilled screw holes, misaligned, like pebbles in one's shoe, sand in a sandwich, f@rts in the Cathedral of the Correct Solution...

your pardon

And here's another one: how, when the cab is mostly built, is it possible properly to screw the baffle restrictor plate in position? Without a right-angle screwdriver?

In my case fat-bottomed cabs make the rockin' world go round, and I want to get the best low-end performance out of these little cabs as possible, so I will try them first with the restrictor plate installed.

Next: one solution.

Best
--aeolos

[aeolos]

One of the optional features of the Omni 15 TallBoy design is a baffle restrictor plate that tunes the cabinet to give more emphasis to low frequencies, at the expense of overall sensitivity. Since these cabs will be used for PA and reproduction of recorded music, and I like strong bass, I want to at least try the cabs with this plate in place.

This plate blocks about a third of the port area. The port is the opening between the baffle board, that stops short of the rear of the cab, and the fixed portion of the back of the cabinet.

Problem: how can the speaker builder install this plate once the cabinet is mostly complete, without a right-angle drill and screwdriver? There isn't room to use the tools I have on hand. There isn't money to buy a right-angled driver-drill.

One solution: make the restrictor plate into a restrictor paddle,and end up with something that looks like this, in plan view:

side view:

front view:

As we see, the restrictor paddle is designed to mount to the baffle board using bolts, with hurricane nuts glued into the paddle itself. This design makes for (relatively) easy removal and reinstallation during testing, and is more robust than plain wood screws would be. In this case the bolts and hurricane nuts are 10-32.

So we need a couple of holes in the baffle board:

And to prevent unwanted buzzing noise caused by vibration of the paddle against the baffle board and/or the back of the cabinet, we need some durable foam (Akasa computer sound-deadening foam here) to go between paddle and back, and some rubber tape to go under the paddle, between the paddle and the baffle board (not shown, but it's 3M real rubber electrical tape).

Here's the paddle ready to go into the cabinet:

Conclusion in next post.

Best
--aeolos

[aeolos]

Conclusion to the restrictor paddle solution:

Here's what the installed restrictor paddle looks like from the front of the cabinet:

The big board in the foreground is the edge of the lower baffle board brace. You can see one of the paddle mounting bolts at left center, next to a speaker-mount hurricane nut. The other paddle mounting bolt is under the lower baffle board brace.

And here's what the installed restrictor paddle looks like through one of the handle holes in the side of the cab (this was a "dry fit" without the rubber tape between the paddle and the baffle board):

Trust me, I have trial-fit the drivers with all 8 bolts in both cases, and they fit! They fit! Easy in, easy out. I like it . I have cut that screw off, that shows in lower left center of the photograph. Those screws must have bitten me 20 times at least.

Whew! The hope is that this is the last of the special-purpose mods required for this cab, whether by my own error or by not having the necessary tools. It is good to be nearing completion of at least one of these cabs, and someday I will have the wherewithal to finish the second... with a whole lot more know-how, as a result of building the first.

Now on to DuraTex for the front of the cab, Formica for the other external surfaces, aluminum extrusion for the edges, and corners. THEN at long, long last it will be time to stuff this box and fire it up to see what hath been wrought. I am ready for that day, let me tell ya. Will publish test results and impressions, and before that photographs of the completed cabinet.

All the best
--aeolos

[Tom Smit]

Aaaah, no doubt, you'll be ready! You've overcome quite some hurdles. All the best!

[DJPhatman]

One question, aeolos: do you have a plan to block those holes if you don't like your "paddle"?

Great looking build, otherwise. I'm more than a little curious about the Formica on the exterior. And the aluminum. Can you give a little more hint?

[aeolos]

Thanks Tom and DJ. This is a remarkable community, and I am most grateful for your and everyone's welcome.

DJ, if it turns out the restrictor doesn't sound good, I'll squirt some PL in those holes and re-DuraTex the area.

If you think of an old-timery Anvil case, you'll have the design aesthetic: flat panels covered in sheet plastic-or-whatever (Formica here), with aluminum angle on the edges, and steel corners. At least for the moment there will be a full grille of black Mellotone cloth on the front, with Bill's specified 1" framework, including square interior corner braces big enough to screw the corners to. Under that will be DuraTex.

The whole front grille and those 4 edges and corners will be a single piece, and use 3/4" aluminum angle between the corners. All other edges will be 1.2" aluminum angle. The removable back panel, the 3 pieces of 1.2" aluminum angle, and those 2 corners will be a single piece too.

So for access you'll need to unscrew many many screws. This is to me (although I quite understand it may not be to others) an acceptable tradeoff for the real gains in abuse resistance and retro visual appeal (again, to me). These things are designed not to blow up. Have thought about using those Eminence limiter lamps and may still, but an equally effective approach is to provide sufficient power to avoid clipping, and then to avoid overpowering the cabs.

So there's a lot of words , hope they help to describe the planned appearance.

Pictures will be better, coming soon.

Best
--aeolos

[DJPhatman]

Kind of like this:

[aeolos]

DJ, you are correct sir!

And I did think about putting the tops on them like that, and still may someday, but not today.

But they will look much like that. The one I'm bringing to completion already does, since it now has the 'mica on all sides except the front. The front is finished with DuraTex, very neat and tough stuff also, never used it before. Extrusion and corners now in hand, but not cut and installed.

The empty box without the aluminum extrusions, steel corners, and grille frame/cloth, weighs 60.6 lb (27.5 kg, less or more) as measured by an electronic scale. So I'm guessing that the completed empty box will come in at about 66 lb, and fully stuffed with 3012 LFs, Alpha 6 ferrite version, Selenium D220Ti with HC23-25 plastic lens horn, L-pads, filters, foam, etc. etc. about 80 lb (36.4 kg). Might be a little lighter, but it still beats a factory JBL 4663 similarly clad in the weight department. Less bulky and easier to move too. Perkins bins (which is what a 4663 is) are sort of cubical. Too bad I don't have one for acoustic comparison. I have a hunch that a single Omni 15 TallBoy built as this one has been will beat a single 4663 for the intended applications, but we shall soon see.

This cabinet is very solid indeed. The Formica and contact cement add yet more stiffness (and weight, yes) to the design. 51 pieces of wood by the current count, and on the order of 180 stainless steel wood screws, with something like 40 T/hurricane nuts and associated bolts. Lots of PL, most of which was indeed oversquirt, but better in my view to waste some PL rather than to have any doubt whatever about airtightness and structural integrity. Will have more precise counts/amounts shortly.

You do not want this thing to land on your foot if you drop it. The cabinet will win and your foot will lose, if you don't have your steel-toed roadie boots on.

Off home now, from work work, to see if I can do something to the purpose on this cab before shutdown tonight. Really getting eager to fire it off.

all the best
--aeolos

[aeolos]

Finally, some progress to report. Family matters took me out of town for a while.

Got Box 1 of 2 fully stuffed and wired, functionally complete. All that remains is the edges, corners, and grille. May add 12" round steel grilles over the 3012LFs, all that would be required is some 1/4-20 nuts, already have the grilles and the speaker mounting bolts would do fine to hold the grilles.

95.2 pounds (43.3 kg) of extremely stout little full-range cabinet. Weighed using a digital strain-gauge scale, so the figure is pretty close to actual. With the corners, edges, and grille(s) probably 99 pounds all up. Hefty little thing. Below are some pictures. As you'll see there is some cleanup to be done. Also, all those edges and seams will be covered by aluminum extrusion. It was far cheaper to get a 96" by 36" sheet of Formica than a 96" by 48"; that's why there are seams at the top and bottom of the back access panel: it was the only way to cover the whole cab out of 1 sheet (that I could figure out anyway). Will be invisible shortly.

Front view of the almost completed Box 1 of 2 (cropped and filled with black around the edges):

3/4 view:

Back view:

All those fasteners on the back panel are 10-24 stainless steel oval-head Phillips machine screws, that screw into T-nuts in the back flanges. The back panel is sealed with neoprene gasket tape.

Will have some interior shots soon, was driven to seal it up and crank it up, could not stand waiting any longer. Have been working on these things SINCE AUGUST but at last have something to show, and hear as well.

Next: initial impressions of my first BFM build.

Best
--aeolos

[miked]

Wow, that's a great-looking cab! Will look pretty badass done up in "roadcase trim." Sorta like the MesaBoogie RoadReady bass cabs that are essentially, a cab mounted in a roadcase.
Cant' wait for more pics and your report!

[aeolos]

Thanks miked! There is plenty wrong with it, as this build thread shows (although it is actually square, unlike the photos that always seem to show it skewed somehow). It has a vaguely ordnance-like appearance to me, that I like.

Built by a complete n00b at cabinet building, it could have turned out worse. I keep telling myself. Whatever else might be said, it is a strong little box.

Dragged it into the bedroom since that is where the stereo rig is, the only way I can test it at the moment (fully aware of the uselessness of results obtained in a bedroom, will test in a half-space soon if all goes well). But at least I can hear something.

In the gray dawn this morning, saw it standing there, somehow reminiscent of the monolith in 2001: A Space Odyssey. OK, it is thicker than the monolith. Also Sprach Zarathustra played in my head... well, a little grandiose. It's just a little speaker cabinet. That will soon be playing Also Sprach Zarathustra, among other things .

Best, and more after a little more testing
--aeolos

[miked]

Also Sprach Zarathustra is a fine test for any full-range cab or PA system for that matter. Those kettle drums will get the woofers a'flappin' for sure, and the horns will give the mid driver a nice workout as well. Throw in the crash cymbals and triangle at the end and you've got a fantastic test song. The ending is the best part; you think the song is fading out, but it comes back LOUDER than before.

[88h88]

That is a super tidy looking build, I know you say you're a novice at this but you've clearly got talent...