OTop12 Build Thread

[Grant Bunter]

Continued with the arrays.

I hope I don't skip anything accidentally.

Arrays are looking good


If you're worried about missing something, just come back to your thread, and tick it off lol...

[miked]

Thanks, Grant. So far, so good. I can definitely tell that I'll need several coats of cement, front and back on the melded arrays. They have a few gaps...in the middle, of course and that weakens the whole structure. Would be nice to be able to get six screws in there to fix them to the array braces. I've seen a few posts about that. I may try it. I'd need to drill out a bigger hole between two of the "cut on both sides" tweets in the middle, but I think it's worth doing, structurally-speaking. The middle screws wouldn't be torqued-down; just "screwed down enough" to lend some mechanical support to the array.

The flat arrays are solid gold. They're flat, evenly glued and much lighter than the melded. Four screws is fine for the flat array, but not the melded. IMO, of course.

[Bill Fitzmaurice]

Thanks, Grant. So far, so good. I can definitely tell that I'll need several coats of cement, front and back on the melded arrays.

I never put cement on the front of arrays. I put masking tape over the joints, then add cement to the back of the array. The cement will seep into the joints. I seldom need more than two coats to do the job. I also put cutoffs from the piezos into the cement. They dissolve in it, tinting it black, while the additional solids make it thicker.

[AntonZ]

Mike, your melded arrays are starting to look good. You may want to rotate the elements in your melded arrays by 120 degr. That way the connections will line up more naturally, making it easier to wire the arrays correctly.

Like so (slightly different, as my elements were mounted alternating).

[miked]

Thanks for the tip and the kind words, Anton. I may do just that...just not sure yet. So many other things to do in order to finish these cabs up. Last night I realized that I forgot about the grill braces. Remembered that AFTER I sprayed black primer in the mouth of one cab. At least it's only one. So I still have wood-cutting and construction to do.

Looking at your pic: Did you completely remove insulation from the total length of the wire? I'd imagine it's no big deal as the plastic pizzers are non-conductive.

I was thinking of doing something similar, b/c cutting 24+ 3-inch pieces of wire and stripping the ends is going to suck. Would be easier to strip the wire completely, thread it through each terminal tab and hit it with solder. Although your wire appears to be solid-core; I bought 16ga stranded. Now I'm not sure.

[miked]

Thanks, Grant. So far, so good. I can definitely tell that I'll need several coats of cement, front and back on the melded arrays.

I never put cement on the front of arrays. I put masking tape over the joints, then add cement to the back of the array. The cement will seep into the joints. I seldom need more than two coats to do the job. I also put cutoffs from the piezos into the cement. They dissolve in it, tinting it black, while the additional solids make it thicker.

Thanks for the tips, Bill. So, I guess you use the masking tape to hold the array together while applying glue? Not sure if I'm that capable at this point. We'll find out how good of a bond is on there later today when I flip the array over to see how much glue if any I need in the front. Being that nobody will ever see them, I'm predisposed to carefully applying some glue on the front of the arrays. Where there's little danger to the elements themselves when gluing the back, that danger is much higher when gluing the fronts at the meeting point b/t the left and right sides. I'll be careful.

[Tom Smit]

Looking at your pic: Did you completely remove insulation from the total length of the wire? I'd imagine it's no big deal as the plastic pizzers are non-conductive.

I was thinking of doing something similar, b/c cutting 24+ 3-inch pieces of wire and stripping the ends is going to suck. Would be easier to strip the wire completely, thread it through each terminal tab and hit it with solder. Although your wire appears to be solid-core; I bought 16ga stranded. Now I'm not sure.

If you look at the picture in the middle of this thread , you may get an idea.

[AntonZ]

I did indeed strip the wire bare. Much easier than installing a large number of short wires. And it is rather cumbersome to solder two wires to every lug. You should not heat those lugs any longer than strictly necessary, as any prolonged heat might damage the elements. And for looks or touching: it is the rear side of the array and they went behind a grill anyway in my cabs. Don't cut the wire to length, then strip. You would end up with individual strands falling in all directions. I stripped most of it, but left some insulation on a few extra inches of sacrificial wire. Then solder in place. A bit of twisting to keep the strands together. Only cut the insulated part off after installing the wire on the array. This doesn't work well with the orientation of your elements, the bare wires might touch and short circuit.

My guess is that the masking tape that Bill used is intended to prevent the cement from pouring out the front of the array. Think of it as an adhesive plaster to prevent bleeding.

[Bill Fitzmaurice]

Thanks for the tips, Bill. So, I guess you use the masking tape to hold the array together while applying glue?

I initially glue them together, using a thin bead of cement, let them set, then apply the tape to the front faces. Then since it can't get past the tape I can glob it on really thick on the back.

[miked]

Looking at your pic: Did you completely remove insulation from the total length of the wire? I'd imagine it's no big deal as the plastic pizzers are non-conductive.

I was thinking of doing something similar, b/c cutting 24+ 3-inch pieces of wire and stripping the ends is going to suck. Would be easier to strip the wire completely, thread it through each terminal tab and hit it with solder. Although your wire appears to be solid-core; I bought 16ga stranded. Now I'm not sure.

If you look at the picture in the middle of this thread , you may get an idea.

You are probably referring to this one:


That would work too, though it's a real PITA to remove the insulation from the middle of the wire like that. I've used that technique in the past and it's OK for wiring up a few drivers together...12 elements, not so sure. But thanks for the suggestion!!! I'm uploading some pics now.

[miked]

And here's your Friday night update!

I put a thick coat of cement on the front of the melded arrays. They both pretty much look like this as this point.



After they dried, i held them up to the light and could see light peeking through in some very small spots. Maybe 2-3 spots on each array and the openings were very small. The cement dries fast, so I'll put another coat on the front tonight and call it good. BTW. I discovered something a bit disconcerting. When I tried to do a test-fit of the melded arrays, they wouldn't go through the array braces. No matter how I tilted it, it wouldn't go through. I double-checked and my braces are exactly 5-1/2" apart. The problem was the soldering/connection tabs on the tweets, they all have to not be facing outwards towards the sides of the cab. So I guess I'm going to have to rotate the elements afterall. I could get it in there by forcibly bending a few tabs, which I did, just to ensure the array sat correctly on the braces (they do), but once the array is wired up, there can be no bending of the tabs. Never seen this noted before, so thought it worth mentioning.

So last night I got all carried away and thought I should spray the mouths of the cabs black. Sprayed one cab and stood there for a sec...something was not right. Wait...where are my grill braces?

So I spent this afternoon cutting the grill braces. Here's an interesting lesson in "picture composition." Note the interesting juxtaposition between the black cab and the white braces.



And that, boys and girls is what "A mistake" looks like. Oh well, problem fixed.

I went on cutting grill braces and came to an opportunity to excel. AKA, a problem. I tried cutting the grill braces for the horn panels at the per the plans 35 degrees, but all my cabs have different angles for the horn panels, unfortunately. They're not off by too much (save for one cab I've nicknamed "Ugly") but the differences are there. How to measure what angle to cut them at? An hour later I realized that if I simply held the brace like so, I could mark the angle.



Thankfully, I have a tilting tablesaw which made matching the angle easy.


Angled grill brace (3L stands for "Cab #3, left side)


Anothher pictures of the braces.


So the time has come to start the finish work! Finally. I thought it best to spackle/sand/roundover the cabs before putting the damping material in, since there will be spackle dust everywhere when I sand. I bought this little ditty at HF the other day, along with 80 and 120-grit paper. Should make short work of sanding.



Spackled cabs everywhere! I enjoyed the spackling part...the end is drawing nearer.







The spackle instructions say 3-5 hours drying time before sanding...I'll just let it sit overnight. I'm pretty sure I'll only need this one coat of Spackle on 90% of the cab. I have 3 pretty deep recessed screwholes on the top of the cab that might need a second fill/sand of spackle. We'll see tomorrow.

So tomorrow:

Drill mounting holes in rear panels and predrill rear panel braces while I'm at it
Sand cabs
Respackle if necessary
Finish with flush trim bits
Roundover edges
Install damping material

Possibly start on soldering up crossovers if there's time. I've decided against tophats in the cabs. The standard "through the reflector" position is too unbalanced, and trying to put it anywhere else has a high probability (for me) of totall screwing up the cab, so I'm not doing it. I'll either be constructing a "tray" of sorts that will go on the speaker stand(s) or possibly getting some metal stands built, ala Pulseman's most excellent stands. (And if you're reading this, Pulseman, how's the weather down there? *hint-hint*)

Thanks for looking.

[bmf]

Should of mentioned this when I recommended the spackle but it can be useful to buy fadding spackle. It goes on pink and fades to white when it is dry. Lets you know when you can sand without worry of hitting it to early. Letting it dry overnight is a better situation anyway though as you can still get shrinkage even after the material is dry enough to sand. If you wait overnight it should sand flat and not shrink in later.

[67baja]

Looking at your pic: Did you completely remove insulation from the total length of the wire? I'd imagine it's no big deal as the plastic pizzers are non-conductive.

I was thinking of doing something similar, b/c cutting 24+ 3-inch pieces of wire and stripping the ends is going to suck. Would be easier to strip the wire completely, thread it through each terminal tab and hit it with solder. Although your wire appears to be solid-core; I bought 16ga stranded. Now I'm not sure.

If you look at the picture in the middle of this thread , you may get an idea.

You are probably referring to this one:


That would work too, though it's a real PITA to remove the insulation from the middle of the wire like that. I've used that technique in the past and it's OK for wiring up a few drivers together...12 elements, not so sure. But thanks for the suggestion!!! I'm uploading some pics now.

I did my tweeter wires like that, but FYI, you don't need to 'remove' the insulation. Just use your wire strippers and pull the insulation apart 1/4-1/2", put the bare wire on the speaker terminal, and solder it. The insulation is flexible enough you can bunch it up to expose the wire rather than cutting those 1/4-1/2" pieces of insulation out of the wire.Hopefully that makes sense. Nice and quick.

[miked]

Should of mentioned this when I recommended the spackle but it can be useful to buy fadding spackle. It goes on pink and fades to white when it is dry. Lets you know when you can sand without worry of hitting it to early. Letting it dry overnight is a better situation anyway though as you can still get shrinkage even after the material is dry enough to sand. If you wait overnight it should sand flat and not shrink in later.

Funny should should mention that stuff; I had a container in my hand at Home Depot yesterday for about 15 mins while I looked at all the other similar products. I thought it's a nifty idea, the color-changing spackle. But I decided against it, just b/c we are using spackle in a non-traditional application to begin with, and I didn't want to mix "new technology" with that non-traditional usage. I was afraid of shrinkage, chipping, etc. In the end I bought plain old-fashioned spackle.

I also let it sit over night, so it's definitely good to sand right now, which I'm about to go do. Last night I got the rear panesl predrilled for the mounting holes. I erred on the side of caution and put 9 screws across and 6 on the sides; every 2 inches, basically. There will be no air leakage from the back panel, no way.

I did my tweeter wires like that, but FYI, you don't need to 'remove' the insulation. Just use your wire strippers and pull the insulation apart 1/4-1/2", put the bare wire on the speaker terminal, and solder it. The insulation is flexible enough you can bunch it up to expose the wire rather than cutting those 1/4-1/2" pieces of insulation out of the wire.Hopefully that makes sense. Nice and quick.

Thanks for this tip; I didn't know about that. I will try that and see how it works out.

[Tom Smit]

Last night I got the rear panesl predrilled for the mounting holes. I erred on the side of caution and put 9 screws across and 6 on the sides; every 2 inches, basically. There will be no air leakage from the back panel, no way.