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Thread: Wood Horns Take II

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    Senior Member Woody Banks's Avatar
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    Wood Horns Take II

    I decided to build a few more wooden horns but needed to reduce the brute force required using the belt sander. I copied a shop jig from a photo posted a few years ago from a fellow DIY in HK. Thanks to a few basic AutoCad skills I was able to put the router roller coaster together. After a few modifications, I was able to carve the proper slope for the A-290 in a fraction of the time required with the belt sander. I glued up a stack of Tiger wood for my test case and everything looked very promising. The next step was to try the jig system on the VERY EXPENSIVE Padauk. This is my first time using this exotic hardwood and will also be my last. My normal go-to adhesive has been Titebond II for several years and has always proved to be strong and reliable. In this case with the Padauk there is something that causes the glue to go into suspension instead of drying and bonding as it should. I have stumped the so called experts and have so far tried six different types of glue. I will give epoxy a try today. The second and third photo shows the wet glue after four days of being clamped in a heated shop.This is killing my shoestring budget. At $8.25 a board foot I will not obtain very many BTU's for the buck when I chuck this project in the wood stove.
    The plan was to pair up the Padauk A-290's / 2450SL's horn combo with my ME150's for a K2 style project. I think I will set this project aside, have two or three Black Butte Porters this evening and start on my 250Ti clone project instead.
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    Senior Member Lee in Montreal's Avatar
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    Is the white stuff the glue that never dried?

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    Senior Member pos's Avatar
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    The original 2450SL is a 1.5" driver. Are you doing a 3/4 reduced version of the A290?
    Or are you using a 2450H 2" driver with a SL diaphragm?

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    Administrator Mr. Widget's Avatar
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    I think some padauk is more oily that other examples. If you wipe it down with acetone before gluing and clamping, I think you'll be OK. I would do a test, and I would try the acetone regardless of the glue you use. Since your failure is so complete, you should be able to clean off the old glue with warm water and scrubbing, followed by acetone to rid yourself of both the oils and drive out the moisture from the glue removal and then re-glue it.

    Have you worked with padauk before? If you don't use a finish with significant UV protection, the bright red/orange color will look like a medium brown walnut in a few years.


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    Senior Member richluvsound's Avatar
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    Woody,*

    ** I second what Widget have suggested .... Teak and Lignum vitae are the same - they heal themselves with an oil when freshly cut . Your notice the saw dust feels damp !

    I have made a few arm-boards from the same wood .

    Shame , they wood look gorgeous . Love the jig too !

    Keep going mate , Rich

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    Senior Member Woody Banks's Avatar
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    I gave the acetone trick a try a few weeks ago to no avail on my test samples. The oil issue makes total sense (cents) though. Because no two boards are identical it stands to reason that they exhibit differing results when you attempt to mate them together. The oil in some of wood is holding the glue in suspension and not allowing it to activate. That would explain why the other three horn halves turned out fine.
    This is my first and last exposure to Padauk. I like the beautiful orange tone of the freshly milled material but was shocked when I saw a sample that was black as coal after only one year.
    I don't look at this as a failure but just another expensive speed-bump in the road of life.

  7. #7
    Senior Member Wardsweb's Avatar
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    Having recently finished my CNC bubinga horns, I can highly recommend the wood. It is very dense and machines beautifully. You can even drill and tap it.

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    Glue issues aside, the router roller coaster is a brilliant concept!
    Show us what ya got: Homebuilt Hi-Fi

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    Senior Member Woody Banks's Avatar
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    Quote Originally Posted by lowpoke View Post
    Glue issues aside, the router roller coaster is a brilliant concept!
    A photo of this device surfaced on a wood horn thread by Ian Mackenzie and again on the DIY Audio Forum. I am not positive, but I believe the credit belongs to the person in HK producing the TAD clones.
    This was an inexpensive alternative to the CNC machine I was forced to sell.

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    Senior Member Woody Banks's Avatar
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    I decided to give the jig setup a try using a five layer baltic birch plywood build-up. The gluing process is much quicker since you are only dealing with a horizontal bonding. The carving process requires between 30~40 minutes per piece. I will probably do a combination of black paint and bubinga veneer on this pair.
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    Hi, great work on these horns. I stop by now and then to check out what the members here produce and am always left impressed!

    I am a cabinet maker and have had similar issues with oily exotics.. I use a polyurethane glue for these type of species. The problem is the clamping time it takes, and the movement while under clamps.

    Polyurethane will work, but as it cures and expands it will bond the wood and swell into cracks. If there is any showing on the exterior of your finished piece. it can be a pain to remove and or cover with finish.

    I have been pouring over the horn thread on Lansing,, I think these are some of the most beautiful speakers ever made.

    I have also used similar router jigs.. and with proper set-up the repeatability is great.. what can't you do with a router!?

    I have recently started working with a local CNC shop, but programming the machines is not my department :/ will have to be a project one day either with router or cnc.

  12. #12
    Senior Member Woody Banks's Avatar
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    I tried a few different stains on the Baltic birch and they all looked like butt so I ended up painting them satin black.
    Send me a PM if you are interested.
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  13. #13
    Senior Member Woody Banks's Avatar
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    Photos taken after three coats of water based polyurethane. I decided to try using brass threaded inserts this time.
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