Otops restarted

[bmf]

So after haunting the sight for awhile I have finally finished all the remodeling on the house. That means I can get back to building the Otops I bought parts for over a year ago. I cut everything and preassembled four units before having to go do a show today. Nothing glued yet just test fitting of parts and screwed. Should make assembly quick and easy tomorrow. I also made a master set of blanks that don't have any angles cut on them. I used a router to clone all the parts in a matter of minutes. just screwed the master to the plywood and let the shank of the bit act as a guide. Worked great. Used a 5 1/8" hole saw to make my phase plug discs. I still need to make the port/handle cuts and fit the landing for the back plate. I should have them assembled tomorrow. Then I can get started on the CD horns. I had planned on building an rtm mold and making fiberglass horns but I will retrofit those at a later date and just go with the wood horns in the plans for now. I have to many new projects at work right now to do an off hours "government" project. Can't tie up the machine time. The curved front I went with made them a little more difficult but I really like the look. Anyway I will try to post pictures of my progress as I go provided I can stay on task this time and life doesn't cause any more interruptions.

[LelandCrooks]

Looks excellent

[bmf]

Thanks Leland

It looks like I will be using crossovers in these instead of biamping as I had originally planned. We are trying to reduce weight in our amp rack and have been buying up all class D's (already changed out the entire monitor rack). Seems silly to buy extra amps and add weight when a correct crossover is already available.

Raining today so I couldn't get anything done. I was afraid to use PL inside a freshly remodeled house. The wife might frown on dropping adhesive on the nice new hardwood floor in the background of the pic I loaded in the first post. I'm pretty sure divorce would slow down the build a little.

[bmf]

A little more progress with some pictures.

Been working on a surprise for the CD horns. Hope to be able to post some pictures of that tomorrow.
Also making a slight alteration to the front of the baffle when mounting the phase plugs. I have to complete the horns before I can implement it though. It plays no effect on the shape or size of the plug.

[bmf]

Well I haven't posted for awhile. I decided to move forward with making fiberglass horns. I am not going to RTM them (molded smooth on both sides in a closed mold) because of time constraints. I am however making a mold for open molding them. These will be smooth on the interior and have a rough glass finish on the exterior.

Got a block together and started machining today. Our engineer who is a much better programmer than me when it comes to patterns posted the path for me. Got the rough path done today and will run the finishing paths tomorrow morning. I should have it sealed, painted, sanded and waxed by the middle of next week. After that the parts are easy to make.

My plan is to pull a master pattern from the temporary wood mold first. If I can pull 5 pieces after that off the temporary I will finish my cabs before going back to make a permanent mold. I will use four for myself and would like to send one to someone of Bills choosing or Bill himself for testing.

[bmf]

I have finished the glass cd horns. I will try to get some pictures up this evening. They came out really good. I do have one problem though. I didn't compensate for the Duratex paint thickness. They fit the naked cab perfectly at dead on 14". This means I will need to route in a small amount of relief in the cabinet to account for the paint. I've been a professional fabricator for 25 years and a process development engineer for the last five. I can't believe I didn't account for this. I get paid not to miss things like this!!

What is the opinion on placement of the horn front? I know it sets back 1/2" on a flat cab. Should I match this distance on my curved front cabs; set it back the 1/2" plus the additional 2; or go somewhere in between? I would think I should stay at the 1/2" so as not to interfere with the coupling of the horns but I don't know what affect the driver setting 2" forward will have. Any thoughts on this would be appreciated.

All that is left is to paint, mount the horns, wire (still need to get crossovers), and add corners and grills.
Really looking forward to FINALLY finishing these cabs.

[J_Dunavin]

Man that's awesome!!

[howiez]

I can't believe I didn't account for this. I get paid not to miss things like this!!

Been in Engineering myself for near 20 years, and I still miss little things like this on my own fun projects. You get so caught up in the awesomeness of the project, and gloss over mundane details like paint thickness!

Awesome work, keep it up...

[Chris_Allen]

Can't wait to see some pictures of the horns

[DJPhatman]

What is the opinion on placement of the horn front? I know it sets back 1/2" on a flat cab.

The distance isn't super critical. As long as there is adequate distance (read this as at least an inch) from the baffle front to the rear of the installed compression driver, you're good.

Should I match this distance on my curved front cabs; set it back the 1/2" plus the additional 2; or go somewhere in between? I would think I should stay at the 1/2" so as not to interfere with the coupling of the horns but I don't know what affect the driver setting 2" forward will have. Any thoughts on this would be appreciated.

Don't sweat it. That short of a distance will not be noticeable.

As for the length of the CD horn, just sand it down a smidge on each end. It won't be seen, anyways...

And,

[bmf]

Well, ask and you shall receive.
Here are some more pics of the progress of the glass horns.

[bmf]

Correction to the last pictures. The one marked "permanent mold" is actually the permanent pattern to make the permanent mold from.

The story continues below:

[bmf]

All four are finished and are ready to be mounted.

There will be a delay of at least a week before anything else gets done.
I am leaving Monday night for FT Sill Oklahoma. My son is graduating from basic and we will get to see him off and on during next week. Wouldn't miss this for the world!

[Grant Bunter]

Looks wonderful!

Have you managed to work out the diffraction rod too?

[bmf]

I wasn't sure if I needed it for the CD horn. I thought it may have only been structural. If that is the case I won't need it as these horns are very strong.
If I do need it to prevent beaming then I have 5/8 glass rod that I can easily add with methacrylic adhesive before installing them in the cabinets.