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Old 14th January 2007, 06:28 AM   #1
owdi is offline owdi  United States
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Default Thinking about building an OB using ironwood (ipe)

I've been thinking about building an open baffle speaker using a very heavy natural wood. I love the texture, color and feel of natural wood, and OB is a lot easier than building a box.

Today, I had the extreme pleasure of handling an ipe board for the first time in my life. Holy ****! It is 40% heavier than hard maple, and two and a half times as hard. I was outside, where the temperature was around 30*F, and picking up this board just sucked the heat out of my hands. It felt more like metal than wood.

Link to detailed description of ipe
Link to description of hard maple for comparison

I can buy ipe heartwood boards that are up to 2" thick and 12" wide from my local hardware store. Two 2" x 12" x 36" baffles will set me back about $80. Based on a density of 62 lbs/sq foot, the baffles will weight around 30 lbs each. Drivers would be the Vifa XG18 and Seas 27 TBFC/G.

I was thinking about standing them up on a solid chunk of granite. I have a friend who is a master tile setter, who could shape and polish the granite any way I need.

The only thing holding me back is my fear for my tools. I've recently spent about $100 on carbide router bits, and I'm afraid this one project could ruin them all.

I tried searching the forums for other projects like this, but couldn't find anything. I'd really like some advice before I embark on this project, especially from anyone who has worked with ipe, or other extremely hard woods.

Dan
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Old 14th January 2007, 10:03 AM   #2
TerryO is offline TerryO  United States
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Dan,
That's some serious wood. Don't know if it makes any difference, but here in the NW with all the rain and flooding, you should be aware that Ironwood (and it's evil twin, Ironbark) don't float. So if the valley floods, it's a real bad idea to grab your speakers and head out the door.



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TerryO
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Old 14th January 2007, 10:41 AM   #3
TerryO is offline TerryO  United States
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About 25 years ago I helped a friend build a 45 foot Alden Malibar Schooner. We used Ironbark for the Caprail, as Teak was not only too expensive, but not nearly as tough. We did indeed go through a lot of blades, but we were doing a lot of cutting as every piece had to follow the contour of the hull. Sharpened a lot of plane blades too.

Workboats often used Ironwood for propeller shaft bearings due to it's hardness and because it also has a natural waxiness that works well as a bearing. Ironbark is darker and has a slightly stringy grain structure that was often used on wooden boats to protect the hull planking from damage from the anchor and tackle. You may have seen those vertical boards at the bows of workboats and wondered what they were.
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Old 14th January 2007, 11:27 AM   #4
Pano is offline Pano  United States
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Tough stuff, that ironwood. I've played around with scraps, but never big chunks.

However, I can attest to dense wood being good for speakers. Back in the 80's we used to use plywood called "Nantex" that was the heaviest, densest, most difficult to cut and drill wood I've ever seen. Like your comment about ironwood feeling more like metal than wood. Nantex plywood was like working with non-resonant steel. Thick steel.

The acoustic results were pure magic. Speaker boxes that had no box sound. Not dead like some materials, just no real sound of its own, or at least no objectionable sound. Don't quite know how to describe the difference between dead and no coloration, but that's how it was.

If your ironwood can do that, and it probably can, it's going to make you very happy. After you forget about how hard it was to work, of course.
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Old 14th January 2007, 01:52 PM   #5
Rudolf is offline Rudolf  Germany
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I believe, JohninCR must have quite extensive experience in working with very hard woods. Look for his nick here and at the OB circle at http://www.audiocircle.com/circles/index.php?board=90.0
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Old 14th January 2007, 10:57 PM   #6
owdi is offline owdi  United States
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TerryO - thankfully I live on a hill, so when Rainier errupts and buries Seattle under 60 ft. of mud my speakers will be spared. If they are buried, my hope is they will someday be excavated and enjoyed by future civilizations :-)

panomaniac - I'm aiming for a very simple design, so I don't have much cutting to do. Three cuts with a circular saw, four cutouts with my router, and lots of rounding with my router.

Rudolf - thanks for the tip, going to search right now.

Anyone know if normal wood glue is sufficient for bonding ipe?

Dan
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Old 15th January 2007, 01:12 AM   #7
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Ironwood is quite oily, so I would go for Gorilla Glue rather than PVA. The dust is an irritant, so make sure you wear a good mask whilst working it..
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Old 15th January 2007, 04:28 AM   #8
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I've used Machiche (called almendro here), which is almost as hard and heavy as Ironwood. The difficult part is getting it ready for a finish. Sanding, even with a belt sander, is all but useless. It will be hard on your tools too. Note that the 62lbs is per cuft, so your baffle won't be nearly as heavy as you think. You may want to consider isolating the woofers from the baffle with a magnet mount.

Being able to use real wood is one of the advantages of OB. Great grain and dried without cracking in a softer wood is what I look for now. Here's something I built recently. The baffle is Cenizaro and the driver magnet mounts are almendro for the extra rigidity where it counts.
Click the image to open in full size.
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Old 15th January 2007, 07:42 PM   #9
owdi is offline owdi  United States
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pinkmouse - thanks for the tip. Althought I've never used it before, Gorilla Glue looks to be easily available.

johninCR - Nice speakers, is that the natural color of the wood? I do have a belt sander, and the boards are already pretty smooth, so I hope I can get a smooth finish. I'm not sure exactly what kind of finish to use yet. My general preference is something that will not change the natural color of the wood, and will enhance the grain.

This project hit a major snag yesterday, scoring a very low WAF. She doesn't like the idea of 12" wide baffles in our smallish apartment. I ordered the Vifa XG18 woofers anyway, and will not experiment with designing some smaller baffles.

Dan
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Old 15th January 2007, 09:51 PM   #10
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Even a belt sander will do next to nothing and wear out a lot of belts in the process. Try a cabinet scraper, which is supposed to be better anyway. Mine got significantly darker with only linseed oil. The only thing I've found that doesn't darken is nitro laquer, but I don't have a spray rig. I'm negotiating with a guitar maker to give me some lessons about finish to do things right. I have several real wood speaker projects waiting for a proper finish.
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