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Old 17th July 2017, 03:43 PM   #1
Eric is offline Eric  United States
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Another FHXL Build
Default Another FHXL Build

This project started nearly a year ago when I purchased a new set of Alpair 10.3 drivers and started breaking them in. Fast forward a few months and it's time to get something built to hold them. I started with a 8/4 slab of figured bubinga hardwood that I found at a local supplier - so much for the "frugel" part of the design...

The bubinga was sliced down the middle so I have a nice set of bookmatched 3/4" thick baffles. It took a LOT of sanding to get rid of the tearout from when the resulting surfaces were planed. Apparently this is a common problem with very dense/heavily figured hardwoods.

I laminated the bubinga to 18mm baltic birch ply, then routed out the driver holes and widened the recess on the backside. Next, I painted the rear panels and the insides of the throat. Because of the two-ply baffle, I glued them up in what appears to be reverse order from Dave's recommendations - I started with the baffle and the bottom, then moved to the top, and finally the folds for the horn.
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Last edited by Eric; 17th July 2017 at 04:07 PM.
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Old 17th July 2017, 03:46 PM   #2
Eric is offline Eric  United States
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So here they are, waiting for the glue to cure and a few more supplies to arrive. At this point, I'm almost sorry that I already ordered quartersawn bubinga veneer for the top and sides of the enclosures because the contrast with the birch ply looks pretty nice...

I am really pleased with the figure pattern on the baffles and have been playing around with some scraps to determine how I want to finish it. So far, it looks like 2-3 coats of 100% tung oil topped off with a few coats of low gloss Forby's Tung Oil Finish (a wiping varnish) looks pretty nice. The tung oil pops the grain and the Formby's nicely highlights the chatoyance of this wood.

Next up are some veneer experiments to see how it behaves before I glue it to the speakers. Still to do is add veneer, flush trim the baffles, hit the sides with a 3/4" roundover, then do the finish sanding. There was a hole in one of the baffles (not sure what caused it), but it was pretty deep and far too deep to sand out. I gathered some dust while I was sanding, mixed it with the wood glue and packed it into the hole, sanded it off, and repeated the process. The result is perfectly smooth with the top of the wood and only visible is you know exactly where to look. I figured this approach would be better than allowing the oil to pool in the hole and soak into the grain sideways when I finish them.

These are getting pretty heavy at this point and they wobble just a bit on the carpet, so I'm thinking of adding either spikes or some sort of plinth to keep the vacuum cleaner from dinging the finished surface.

At this point, I have just enough left over bubinga for a front baffle of a matching center speaker.

Question for those that have built these already: Is there any appreciable difference between Polyester stuffing and Wool stuffing for the folds of the horn? There is no appreciable price difference between the two for me.
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Last edited by Eric; 17th July 2017 at 04:02 PM.
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Old 17th July 2017, 04:04 PM   #3
zman01 is offline zman01  Bangladesh
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Eric,

Beautiful work.

ave you sealed up the cabs?
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Old 17th July 2017, 04:08 PM   #4
Eric is offline Eric  United States
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Thanks, Zman. Nope, cabinets are still open waiting for felt and stuffing.
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Old 17th July 2017, 04:32 PM   #5
zman01 is offline zman01  Bangladesh
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Quote:
Originally Posted by Eric View Post
Thanks, Zman. Nope, cabinets are still open waiting for felt and stuffing.
Hi Eric,

You might need to place some stuffing below the driver. To help keep the poly fluff in place, you might consider fixing some netting material or a few pieces of string say 8-10 inches below the driver.

Have a question regarding the chamfer you've done on the backside of the baffle. The plywood looks chamfered well, but there's a little bit of tickness being added by the hardwood baffle - how much is the material thickness?

Regarding your question on stuffing material, my understanding is that the stuffing should be hollow fill poly fibre, and the lining can be wool/denim/jute felt.

Last edited by zman01; 17th July 2017 at 04:34 PM.
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Old 17th July 2017, 04:54 PM   #6
Eric is offline Eric  United States
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The next step is to add some netting under the driver as you indicate, so the stuffing doesn't fall down to the bottom of the cabinet. I'll probably run a few strands of Cat5 wire, staple it in place, and put a few beads of glue on top of the staples to hold it securely.

I'm guessing the hardwood baffle is somewhere near 16-17mm thick. I didn't measure it when I was finished sanding, but I can measure precisely tonight. The hardwood is laminated to 18mm BB, so total baffle thickness is just less than 1.5 inches. I recessed the driver hole by 13mm so the driver sits flush with the baffle surface. Thus, the screws that came with the Aplair driver will pass through 3-4mm of the bubinga and will reach into the BB ply by 2-3 turns or so. I lined things up by hand before chamfering - the mountings screws will remain fully within the wood and have plenty to grab hold of.
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Old 17th July 2017, 05:32 PM   #7
Ray21 is offline Ray21  United States
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Nice work. That bubinga is gorgeous!
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Old 17th July 2017, 05:40 PM   #8
Eric is offline Eric  United States
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Quote:
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I'm guessing the hardwood baffle is somewhere near 16-17mm thick. I didn't measure it when I was finished sanding, but I can measure precisely tonight. The hardwood is laminated to 18mm BB, so total baffle thickness is just less than 1.5 inches. I recessed the driver hole by 13mm so the driver sits flush with the baffle surface. Thus, the screws that came with the Aplair driver will pass through 3-4mm of the bubinga and will reach into the BB ply by 2-3 turns or so. I lined things up by hand before chamfering - the mountings screws will remain fully within the wood and have plenty to grab hold of.
Oops - just discovered what I posted above is incorrect - I'm mixing my units of measure here. The driver recess is 13/32" leaving much more hardwood thickness for the mounting screws to grab. The screws will still only hit 2-3 turns into the BB ply.

Here is a profile image of the driver cut out - there is more thickness left behind than I removed.

Ray: I really like the Bubinga - interesting part is that right now ALL of the wood is still raw, can't wait to start finishing it!
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Last edited by Eric; 17th July 2017 at 05:48 PM.
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Old 17th July 2017, 06:31 PM   #9
chrisb is offline chrisb
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Eric - that Bubinga will probably pop like crazy once you get some finish on it. Did you already mention what the plan was for the side panels / top? With a decent R/O sanding down to 220G, the BB can be quite presentable with just come clearcoat as well - but then you might already know that.

Looking really good
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Old 17th July 2017, 06:57 PM   #10
Eric is offline Eric  United States
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Chris - the plan for the top/sides is quartersawn Bubinga veneer - should arrive in another few days. I've been reading a bit about how to finish Bubinga (as well as playing around with my scraps) and it seems the consensus is to sand to a very fine grit (600+) to help accentuate the grain.

Zia - found your old thread about stuffing type and am having trouble connecting the names you've used to actual products. Is something like "Poly-Fil" Premium Polyester Fill a reasonable choice here?
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