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

[aeolos]

biggerrigger, I agree with you... except there is already so much time in these cabs, and just this one cab that is this far along... I dunno...

The thing that decides the question is, those 3012LF woofers actually DO NOT fit, now that the back flanges are in the one cabinet I've got drivers for . They can't make the turn to go up against the baffle. Bum city, but it is entirely my own doing: ignoring both plan and model, I aligned the vertical internal brace with the edge of the midrange horn baffle, as some of the earlier photographs in this thread clearly show.

It looked so much nicer that way you see.

But since this egregious error must be fixed, any time to make a double-glazed window, to enable gazing upon the cabinet's inwards by battery-powered LED illumination, is gone. Maybe the next cab eh.

Fortunately I guess, the fix is relatively straightforward: shift the blocking portion of the vertical brace to the right as viewed from the back of the cab. Will of course document the operation and post the photographs here as a warning to other lovers of straight lines.

Besides, those crossovers don't really look as good in person as they do in the photographs here. Downscaling those images hid many a defect. Now next cabinet, they really will look that good, with the benefit of the experience building this first set.

And the second cabinet will not require internal surgery to mount the woofers either, for the same reason. Already the baffle board in the second cabinet has precisely-aligned hurricane nuts that enable mounting the unmodified woofers without a struggle, using 1/4-20 bolts and nuts, unlike this first cab that requires all of the driver mounting holes to be drilled out to 23/64".

Live and learn, yes indeed
--aeolos

[aeolos]

State of the Cabinet-note the position of the internal vertical brace, which is wrong and prevents the woofers from being mounted. This brace will be cut top and bottom, about 2" from the ends, and displaced 2" to the right as viewed from the rear of the cabinet. All existing attachments to the distal ends of the braces will be preserved.

Dry fit of back panel:

Front views:

Photos of the fix and resumption of progress coming when available.

Best
--aeolos

[Tom Smit]

Bummer.

[miked]

So all you have to do is cut out that vertical brace and the woofers will be able to fit? Have you checked to see exactly how much material needs to be removed from the brace in order for the woofs to just squeeze by? What I'm saying is that maybe you only need to grind away a 1/4" deep by maybe a few inches long and the woofs can squeeze in. This is similar to what has to be done in Titan subs where the access opening is very slim. The flanges get ground down a little, in the middle, to let the drivers' magnet squeeze in. Please check before you go cutting things out. That vertical braces is what, 3" wide? Even if you cut 1" deep by 6" long it would still be plenty strong. CHECK.

ALSO: If notching out the brace truly won't work, then just cut a section of it out, mount the woofers, then cut a longer "patch piece" to rejoin the two separated ends of the brace. PL and screw it in and it'll be plenty strong. No need to destroy a beautifully-built cab.

The horizontal cross pieces on the back panel flange aren't in the way, are they? If so, just chop one out and reglue later.

[88h88]

I haven't built one of these so it took the pictures before I realised exactly what your problem was. It's a shame you're going to have to perform surgery but it's still a super clean build.

[aeolos]

Thanks for your good words gentlemen! It's not as bad as it sounds I think, will get a picture of the proposed operation up here when possible. Absolutely swamped with work work at the moment, better than the alternative of course.

miked, I've looked at the amount of grinding that would be required and it's a lot, both of that vertical brace and of the back flanges. Will make absolutely sure as you suggest, but at the moment the best (and even easiest) fix looks like to cut the vertical brace loose top and bottom, and from the horizontal braces as well (5 cuts total), move the vertical brace to the right 2 inches, and refasten it with screws and PL, with the probable addition of little plates to strengthen and stiffen the joints.

By the way, once the back flanges were in, that 80-100 Hz ring in the cabinet was gone, gone, gone. Hit it with a rubber hammer now and it just makes a whacking noise instead of that poom it made before. Very strong and acoustically dead box, very nice, and it will be just as nice after the fix.

Best
--aeolos

[Chris_Allen]

Can you front load the drivers and is so, what would the effect of the sound be?

[aeolos]

Chris, that is a most interesting suggestion, many thanks. It is a great thing to have the benefit of the community that has assembled around Bill and his designs. I'm not sure what the performance effect would be. It would add internal volume to the cabinet and alter the dynamics of the horn, certainly; Bill would be the authority on this one. Have already fiddled with his design to some degree, but even I hesitate to make a change of that magnitude .

The hurricane nut flanges are on the outside at this point, and the nuts are glued in place. I'm sure they will come out, but they might bring a fair bit of the baffle with them when they come. Or, could put a gasket on top of them...

Have already stolen some of the internal volume with the handle and those big crossovers of course, so this would give it back. But intuitively the move-the-brace solution seems to pose less risk at the moment. I'll show the operation plan when possible; it's pretty straightforward, inside my head anyway. We have already seen that the inside of my head is not particularly straightforward.

Hmm, and thanks again
--aeolos

[88h88]

Front mounting them would look pretty bad ass actually.

[miked]

Not sure if the t-nuts are epoxied in. If they aren't, they will come out easy enough. If they are, don't mess with them. If you tear up the baffle, the whole cab is toast. I would just go with the fix action you've described. Cut the entire brace assembly out and move it over. Be sure of your NEW mounting location. I.E. make sure you don't trap the drivers in there. They may need to come out someday.

Don't worry; your cab will be just fine after the fix. Braces are braces. As long as they are in there and strong, that's all that matters. Press on, good Sir!

[David Raehn]

The benefit with those nuts is that they are through-threaded. If the end-all decision is to front-mount, you may through-bolt your drivers in place and then use a fender washer, lock washer and nut from behind to secure the whole assembly.

Hope this helps.....

[aeolos]

88h88, it would look good. The plan was to put those steel grilles overs the woofers, then a cloth grille overall, so none of this will be visible, unfortunately.

draehn, your solution would work too, if the fix is to front mount.

And miked, the nuts are held in place with... um... Gorilla Glue . It does expand, in fact it foams, and it does let go fairly easily, as I found when trying to correct the erroneous position of the hurricane nuts a while back. But some of the top ply comes with the nut.

So here's a hack at showing the plan: a 'shopped photograph showing the cuts, and then another showing the moved brace:

The cuts:

The moved and refastened brace:

Sort of Frankenstein-looking but it should work I think, without stealing too much more internal volume.

Plates on both sides of the new joints btw. Once I had a broken leg "fixed" with a plate on one side only. The screws holding the plate fatigued and broke, and so did my leg again when the plate let go. That was an interesting educational experience.

Best
--aeolos

[David Raehn]

Just move the whole brace to the side just enough to clear.....

[aeolos]

But draehn it was so much fun munging the picture. Used time during a boring training session for the purpose.

Also that vertical brace is PL'd both top and bottom, as well as screwed. No doubt it will chisel off, but it seems likely that would involve collateral damage.

The proposed solution does not disturb any existing joints, nor does it add any joints to the exterior panels. Those were two of the guiding principles in the design of the fix. Have considered adding vertical members top and bottom to make triangular trusses, but it seems unnecessary, if the point of that vertical brace is to dampen vibration of the bottom panel and support the horizontal braces that dampen the side panel.

Will be some time before I can get to it, so there is time for thought.

Best
--aeolos

[David Raehn]

But playing in 'paint' is sooo much fun!