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

[aeolos]

Finished the crossover and wiring harness for one of the cabs . Here's a photograph with captions:

More soon
--aeolos

[88h88]

Damn those are pretty. It's almost a shame they'll be hidden away inside!

[aeolos]

Thanks 88h88! Even if nobody else will be able to see them once they are built into the cabinet, I will know they are in there .

Even my wife said "those are pretty in a nerdy, man sort of way." Now that's an achievement, in this household.

All the best
--aeolos

[LelandCrooks]

Nicely done.

[aeolos]

Thanks Leland, you and 88h88 make my day. Gotta go work on a research project for "real" work now, would much rather just keep going on this cabinet. I cannot wait to hear what it sounds like. But I will .

Will be talking to you about the second cab as soon as funding appears. For some reason Jerry Jeff Walker comes to mind:

"Now we're waitin' on the check
To come sneakin' down the hall
Like that old time feelin'
That we never should have ever
Put the record out at all..."

Sometimes it takes a while for the check to appear, even when one has earned it, which I have not, yet.

Therefore, off to apply nose to grindstone. A man must carry on.

All the best
--aeolos

[Grant Bunter]

Hi aeolous,
You need to come up with a plan about how to block off those 1/4" jacks if your using speakon cables to drive the cabs.

Great work so far, keep it up

[aeolos]

Thanks Grant! Do you mean I need to be able to take them out of circuit? The actual jacks are the 1/4" "deep cabinet" style that can easily be sealed by putting a glob of silicone or PL on the back end, and I will be sealing the Speakon connectors (actually Switchcraft, not Neutrik) the same way.

I could put a DPST switch on that dish, I guess, to take the 1/4" jacks out of circuit if necessary.

Can you clarify? But in any case, many thanks for your good words and the pointer!

Best
--aeolos

[DJPhatman]

He meant to block them from leaking air. I suggest you do a "cigar box" behind the jack plate to seal off the cabinet. It is quick, easy to fit, and your only worry is if the wire hole is sealed around the speaker wire.

[aeolos]

Thanks DJPhatman, you guys are a tremendous help. I did confirm that those Switchcraft Speakon-like connectors leak a little bit through the slots that the connecting lugs come through, and the 1/4" deep-cabinet jacks similarly leak through the small slots that the connecting lugs come through. These are not the usual 1/4" jacks that would allow significant air to pass, but are almost 2"-long threaded steel tubes with an interior phenolic disk on the inside-the-cabinet side, but they will be sealed nonetheless. Where they meet the dish, on the inside, there is already a 3/8" stainless steel washer bored out to accomodate the jack tube. On the outside of the dish they have a fairly wide collar. Those jacks are almost 40 years old, and have been cleaned up with DeOxIt.

My plan was to squish elastomeric sealant into those slots using a caulking gun and fingers, taking care not to goo up the electrically-connecting surfaces, and likewise seal the mounting holes in the dish. Finally the same sealant would be applied to the lip on the dish as it is attached to the cab with 4 #10 sealant-coated panhead machine screws (I would be doing the sealant-coating).

The sealant I'm talking about is a colorless transparent material that reeks of toluene/xylene/other brain-rotting organic solvents, much like the Testor's "airplane glue" of old, except that when it cures it is rubbery, not brittle at all.

Grant tried to talk me out of it but I'll be covering the cabs with matte black Formica, then edging them with aluminum extrusion, so this sealant will be between the steel dish and the Formica. I'll be mounting the tweeter horn and the recessed handles the same way, except for the handles I'll be using hurricane nuts instead of screws. Actually only one handle is inside the box proper; the other one is in the exterior side of the bass horn. These are the smaller Penn-Elcom recessed handles with the steel bar and plastic dish.

While we're on the subject of airtightness, the plan for the large removable back panel was to apply neoprene tape to go between the panel and the back flanges, and once again use hurricane nuts to fasten it to the flanges.

Will this deal with the leakage you think?

Many thanks for your help and advice, no fooling
--aeolos

[miked]

By "neoprene tape" are you referring to gasket tape? You could use weather stripping that wasn't too thick, but gasket tape is what you want. This stuff: http://www.parts-express.com/pe/showdet ... er=260-542

You want to keep as much air inside the cab as possible...preferably ALL of it. Anything you can goop silicone (or whatever you're using) on without gumming connections up, do it.

By the way, your crossovers are works of art. Beautiful workmanship and attention to detail. Positive SHAME that nobody will see them! Heck, I'd almost print a color picture of them and tape it to the back panel so everyone could ooooh and ahhh!

[aeolos]

Wow miked, what great words, and thank you. Yes, that's the tape I was talking about. The goal for those cabs is to adhere to the plan: absolutely airtight.

Maybe I could make a little window in the back panel and double-glaze it with that same Lexan that the filters are built on, and install a battery-powered LED inside the cab so people could see what's in there. Put a normally-open pushbutton SPST switch on one side of the leads from the battery to the LED. Hmmm. Hmmmmmmm.

Must resist!

Once again thanks for your encouragement, profoundly appreciated
--aeolos

[bitSmasher]

This thread makes me want to build a 2x12 Omni... why? because it looks awesome, if nothing else

[aeolos]

Thanks bitSmasher! It's a good design, is why it turns out looking good .

Here's a good example (and I'm sure there are many others): http://billfitzmaurice.info/forum/viewt ... 30&t=18215

And here are the back flanges curing:

and here they are ready for installation, filled and sanded:

For some reason the back flanges seemed like a mini-project all of their own, took a while to complete.

In fact there are 4 mini-projects (at least) involved in building an Omni 15 TallBoy, or so it seems to me:

• the baffle board (what we used to call the motor board)
  the horn
  the filters and wiring harness
  the back flanges

These are certainly milestones if they're not mini-projects.

Now on to installation of the back flanges and the removable back panel itself. At this point we start in on the Formica, since the removable back panel will be held in place with 10-24 stainless Phillips oval-head bolts over stainless finish washers, and plain old steel T-nuts. Lowe's wanted $4.25 for a (1, one) stainless steel 10-24 T-nut. Keep it fellas, my word!

more soon
--aeolos

[miked]

I agree on the back flanges being a "mini-build." Being that they have to be 1" thick, you have to glue up two pieces of BB, then cut strips out of it. And if your cab isn't totally square, you'll need to sand a bit here and there off the end of this strip or that strip to get them to fit properly. Took forever to do with my 4 OTops.

[biggerrigger]

LED's would be so cool to show off your x-overs. I would opt for the viewing window if it were me.