BillFitzmaurice.info

Hmm, that IS an interesting idea. Two OTops aren't small, but they aren't DR280-sized either. But I am more concerned with safety than appearance. I sure appreciate the idea, Bruce. It's great that I've got options.

I figured I owed you guys a real update with some pics. Got a bit more done tonight.

First two cabs are "complete" except for the rear panel braces (which I cut up tonight) and of course, the arrays. I haven't trimmed the horn panels flush with the front yet; remember, my cabs aren't perfect. In hindsight, when laying in the horn panels I should've focused entirely on lining them up correctly with the lines I so painstakingly drew on the bottom panel, but instead I obsessed on making the angle cut on the horn meet with the baffle perfectly. Obviously, that was a bad mistake. More work cleaning them up, but so far, I'd bet they're airtight!

Front shot of first two cabs


Rear shot of first two cabs. Look closely and you can see where I've chiseled away the PL so the rear panel braces can reach all the way across and mount cleanly. THAT took awhile.


Second two cabs in the oven. The cab closest to you is Cab#3 and it got it's second side glued on tonight.


Rear shot. I had uniform squeeze out on those side panels (top of pic) but had peeled some off already. And it wasn't dry enough yet. And I had no gloves on. Great job, Mike.


Rear panel braces. The black dots indicate where the screws for the rear panel will come through (my rear panels are already predrilled for screws). So, the black dots tell me where NOT TO shoot brad nails when I secure the braces to the cab top/bottom/sides. Now I just have to remember that the dots mean that, and not "shoot here." Hey, I go with whatever strikes me at that moment.


Tomorrow I'll start attaching the rear panel braces. I'll be able to get 3 of the 4 cabs done. I'm very thankful that I'm putting blacked-out grills on these things. My horn mouths look like crap with PL all over the place. I plan on shooting two good coats of black primer in the horn mouths anyway though. You shouldn't be able to see a darn thing then, which will be exactly the point.
More tomorrow. Thanks for looking.

OH, a related question. When shooting black spray paint into the rear chamber, should the driver spacer ring be taped off? I.E. should I not get any paint on the surface where the speaker's gasket will rest against? I'm thinking "Keep it clean" but figured I'd ask anyway since that step is coming up soon.

We're getting there! Glued the last side on the last cab and started attaching the rear panel braces.




Clamps, clamps...you can never have enough clamps. I even broke out the ancient 3" c-clamps for this job.


And finally, being that I'm out of clamps, so can't go any further until tomorrow, I got around to actually testing/checking the 40 piezos I bought.

The testing rig. Difficult to make out but you can see the tweet on the desk, to the right of the laptop. I used alligator clips to attach to the tweets. Ran pink noise off the NCH Tone Generator program. SO handy, that little program is.


I'm very happy to say that out of the 40 piezos I bought (I only need 36 for the 4 cabs) there wasn't a single dead one in the bunch. 4 of them are lower in volume than the other 36. What luck, huh? I need exactly 36 and I've got 36 good ones. Now, out of those 36 roughly a third just seem a bit louder than the others. All the others are roughly the same...to my ears anyway. I'm not planning on sorting them by db range or something...I've got 36 good ones. However/whatever array/cab they wind up in, they wind up in.

I plan on marking the + terminal with a dot of nail polish; that'll make things easier when it comes time to put the elements back on the housings after glueup. I stole that idea from one of you guys, except the person I'm swiping the idea from used red stickers. I've spent so much money on the little incidentals...I'm not buying stickers. My wife will just lose one bottle of nail polish...out of the 341 she has, I doubt she'll notice.

This weekend will be a big one, not only for construction, but for figuring out what I'm going to do AFA mounting/top hat goes. I plan on mounting a driver in one of the cabs and attaching the back panel. Then I'll balance the cab on a dowel and figure out where the COG is. I do realize that the arrays are not mounted, nor is are the crossovers mounted either. But I'm figuring the array in front, the crossovers in back; should roughly balance each other out for an effective zero change in COG. If I didn't have a warm fuzzy about that, I wouldnt continue.

If it winds up that the COG isn't in a place where the tophat can come clean through, i.e. not hit the baffle or driver basket, I'm probably going to pursue other options. Such as a shelf or scaffold to mount them on, or possibly figuring something out with those bolt-on tophats that I don't really care for, but darn if there's really nothing else out there. Man, how I wish I'd gone with the Neo drivers; then all this extra fussing wouldn't have to be done.

More tomorrow!

It may LOOK like I can pick up Russian radio with this thing, it's really just another OTop getting it's rear panel braces on.



Usually, I have enough clamps for whatever I'm working on. In this case, building 4 OTops, I could've used another half dozen clamps. But I'm already over-budget, so I'll continue tomorrow morning. Normallly I like to let PL dry for 24 hours before removing clamps, but the braces are brad-nailed in and it's humid and 89 degrees in my garage; I think 14 hours in that and the PL will be just fine.

More clamping goodness!!!






Tomorrow morning I'll attach the last of the rear panel braces and let the cabs sit until the evening. Then I'll finish lining the cabs with damping material. I'll have to use spray adhesive, whcich I absolutely HATE. Every time I've ever used that crap, it's been equivalent to trying to spraypaint outside on a windy day. The crap goes everywhere but where you are aiming, it seems.

I have a bunch of trimming to do with flush trim bits, but I'll wait until Sunday for that as I want to mount the rear panels (just w/a few screws) so I can completely trim the cab edges. One or more of the cabs may or may not be uh, exactly square. Nobody but one of us would ever know after I get done though. Let's just say we all know that Duratex and corner protectors hide LOTS of sins.

No pics now because the pics I'll post tomorrow will be well worth it. The rear panel braces are done. I ran the top and bottom-bearing flush trim bits on all sides except the back of the cab. Those two bits are livesavers! The cabs look so much better without the various 1/16" to 1/4" overhangs. I"m sure those of you who have built OTops before know what I'm talking about. Unless my woodworking skills suck that badly that you're saying "HUH? Wut do ya mean, the cab ain't square?" Whatever. Flush-trim bits to the rescue, FOR THE WIN.!!!

On the schedule for tomorrow:

1. Attach rear panels with a few screws.
2. Flush trim the top and bottom panels with the rear panels.
3. Attach the array braces.
4. Build the array cutting and array gluing jigs.

The array cutting jig has me a bit concerned. As far as I can see, the array cutting jig assumes you have a TS sled set up for a 45-degree cut. I do not. I have a nice sled that I built long before this build; it's setup for straight up 90-degee cuts. I won't do anyting to mess up that sled b/c it's perfect, pretty much. I'm thinking I can use the TS miter gauge and the tweet cutting jig to get the 45's I need. I'll figure it out.

More and more pics, tomorrow.

I made two mini ts jig for the tweeters. One for the straight cuts (sides), one for the 45 degree cuts. A small jig is enough, the tweeters are small. The small size can trick you into feeling relatively safe. But on the table saw I feel the smaller the parts, the more dangerous the cut. Do not cut your fingers off, it is not worth it. Have something in place to clamp the tweeters in place for the cut. I believe Harley or Leland have posted pics of their jigs in the past.

miked wrote:As far as I can see, the array cutting jig assumes you have a TS sled set up for a 45-degree cut.

Just build a little jig that butts up to your fence. Hold it tight and go slow. The angle cut is the safest - the blade is pointing away from your delicate digits.

Thanks guys; I'll be very careful. Good idea on using the existing TS fence, Bruce. I'm building the cutting and gluing jigs as we speak. Some more pics to tide you all over.

Array braces in place. These were a bit more of a PITA than I thought they would be, especially the angled braces. I thought for a split second about just going with straight arrays for all the cabs, to avoid all this jig mess...but just for a second. I guess I also need to attach the grill braces, right? Better to do it now, before I spray paint everything in black primer. Need to read the plans on that...not sure how far back the grill braces should be from the front edge. Also, I'm not planning on putting any grill braces on the horn panels; just on the top and bottom of the cab. Seen a few OTops done like this...doesn't seem to hurt anything.

Straight array


Angled array

I'm a little confused on what to do about grill braces. I'm not sure whether to:

A. Cut 1" square pieces of 1/2" ply and put 4 across the top/4 across the bottom
B. Cut longer strips of 1/2" ply to give the grill more contact points

Would full-width grill mounting strips block too much sound coming out of the horn mouth?

The tweeter cutting jig is glued-up; been drying about an hour now. Going to go eat dinner; by the time I get back, it should be dry enough to cut the two slots. Tonight I'll fit the backs to the cabs and flush trim the rear cab edges. I love my flush-trim bits. What lifesavers (pridesavers?) those things are.

Here's how I did mine. Plywood strips. The ones on the sides are beveled to keep 'em straight.

Great pic. Thanks, Bruce. So you did make beveled strips for the horn panels, huh? I wonder if I can get away without those? I have some time to mull it over as I'm not planning on bondo-ing and priming the cab for a few days.

I'm about to start cutting piezos. Made a nice jig and it sits so nicely inside my TS sled. See? Jig in a jig.





Made a test cut with one of the "low volume" piezos and discovered that for this stage, I don't even have to remove the piezeo element b/c al that needs to be cut is the frame. Being that I will be rotating the elements to make wiring easier, I should not have any problem with screw lugs hitting each other, correct? I do realize that when I do the 45-degree cut, one of the barrels will get trimmed. I will be removing the piezo elements for that cut.

Oh, BTW: HOLY CRAP, there's thousands of bits of black plastic EVERYWHERE, and I've only cut one tweet!

*EDIT*
Bah. I can see I was incorrect; the barrels DO need to be cut when you trim the top/bottom of the tweet. The barrel part that the screw threads into does not come off the tweet body when you remove the element. Guess I gave to remove the elements before cutting afterall.

miked wrote: Guess I gave to remove the elements before cutting afterall.

I don't. I cut screw heads and all, it only takes a smidge off them. I use an abrasive blade, there's much less plastic dust that way.

miked wrote:Guess I gave to remove the elements before cutting afterall.

You don't have to if you don't want. My piezos came from the batch that were glued in and you couldn't take 'em out. The saw blade went through the edge of that screw like butter.


Edit....I guess great minds think alike...

Thanks, Bill and Bruce. I went ahead and cut through the screw heads. I didn't put on my laminate blide either; I just left the 50-tooth combo blade on...and it seems none the worse for the wear. Because my TS sled is 3/4" thick and the tweet jig is 3/4" thick, the TS blade couldn't go high enough to completely shear the screw. There is maybe 1/16" of the screw not cut. Figures, right? I can always hit that with the Dremel if it causes a problem.

For those reading this that are curious about how exactly to cut the tweets, a few pics. FIRST THOUGH: Don't even attempt to cut the tweets without building the tweet cutting jig! It makes this very dangerous task easy...though it's still dangerous. AND you NEED to wear safety glasses; preferably, the full-coverage cup-style glasses with the elastic headband.

I did discover that if you try and push the jig through the blade too quickly, the screws can get torn out and hurled at your face at 100mph. It hurts like <--hurts like that Wear goggles; you're only issued one pair of eyes.

Uncut tweet sitting in jig. Notice it's in Slot #1.


Run it through the blade and you get this


Move the tweet over to Slot #2. Note that the previously cut side is against the fence


And that's how you trim the top and bottom of the tweeters.

Here's some array porn!


Note that the array isn't wired up or even glued together yet. If it looks half this good glued up, I'll be a happy camper.

What's better than one not-wired-or-glued-up array? Two of them!


Oh, and yeah, you wind up with a bunch of little plastic sticks. I have the black PVC cement, so really have no use for these things...but it's an interesting pic.


I also cut the 16 tweets (top and bottom) for the 2 melded arrays I'm building, but I stopped there b/c I'm confused about the top and bottom tweets of the melded array. The plans say "cut the bottom frame off one, the top off the other." I'm confused b/c the tweets are symmetrical. If I cut the "top" frame off one, I can just flip that upside down, and now I've cut "the bottom frame" off, no? Is the "top off one, bottom off the other" b/c after you cut the 45, you have to flip one tweet to get it to meet the other at the 45-degree angle? I think I get it...there's a little clarity there, but I'm still not sure.

I am thinking it might be best to cut all the top/bottom tweets at the 45, and then determine which edge to cut off. I have 3 spares, but would rather not have to use them.

I don't want to screw this up. Would someone please expain the process of cutting the top and bottom tweets? Thanks.

Tomorrow: Finish cutting the piezos and either glue them up, or continue trimming the cab. Or solder the crossovers. Or one of about 39 tasks left.

miked wrote: I also cut the 16 tweets (top and bottom) for the 2 melded arrays I'm building, but I stopped there b/c I'm confused about the top and bottom tweets of the melded array. The plans say "cut the bottom frame off one, the top off the other." I'm confused b/c the tweets are symmetrical. If I cut the "top" frame off one, I can just flip that upside down, and now I've cut "the bottom frame" off, no? Is the "top off one, bottom off the other" b/c after you cut the 45, you have to flip one tweet to get it to meet the other at the 45-degree angle? I think I get it...there's a little clarity there, but I'm still not sure.

I am thinking it might be best to cut all the top/bottom tweets at the 45, and then determine which edge to cut off. I have 3 spares, but would rather not have to use them.

I don't want to screw this up. Would someone please expain the process of cutting the top and bottom tweets? Thanks.

Ok, I'll try lol

For each melded array, there needs to be 4 of the piezo's done with cut no1 only.

The uncut edge forms the very top (2 piezo's) and the very bottom (2 piezo's) of the melded array. Much the same as the flat array.

All piezo's inbetween have cuts 1 and 2.
Then all piezo's have the 45 degree cut, but pay particular attention to the orientation of the piezo you are cutting, especially for the top and bottom ones.

Remember, you're working upside down now, so, for the piezo that ends up being top left of the array when completed, the uncut edge is furthest away from you on your cutting sled/jig, but gets placed on the right hand side of your assembly jig.
The other top piezo is cut at 45 degree with the uncut edge nearest to you on the sled/jig, but rotated to place on the left side of the assembly jig with the uncut edge uppermost.

For the bottom piezo's, it opposite, so
Uncut edge nearest to you, goes on the right hand side of the assembly jig.
Uncut edge farthest away from you, rotate to place on left hand side of the assembly jig.

All the piezo's inbetween can just be run through, rotating every second one to place on the left of the assembly jig.

Hope this helps...