Kofi Annan in: "Kofi's Kirishima" - diyAudio
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Old 29th December 2012, 01:11 PM   #1
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Default Kofi Annan in: "Kofi's Kirishima"

Hey!

So, Kofi's still got some vacation time and is looking to start making a Kirishima today for his old Fostex 206E drivers. I know it's a big build, but my room is pretty big and could use the extra bass.

So, here's where you come in--- you have to stop me from screwing everything up. You'll need some information first, so here are the details:

Room size: 24' x 12'
Ceiling: 8'
Amp: 300b SE or Baby Huey EL84 P-P

I'm headed to Lowes to get some plywood as I can't get easy access to better plywood. Here's what I plan to use:

Plywood

I'll need 4 pieces of the 48 x 96 ply since I plan to make the full deflectors. I realize there may be better ply out there but Lowe's will make some of the cuts for me, which I will need as I don't have a huge table saw and will be working alone.

Here are some questions:

1. I plan to butt joint the pieces-- I'm thinking about using the Kreg Jig to make some easy pocket holes, which I will plug to keep the surface level. Any other easy jointing ideas?

2. Will the 206E work well in the Kirishimas or so I need to get the newer 206 eN to mate with them?

3. The plywood will likely be a little thinner than 3/4. It looks like the Kirisihima design accommodates thickness variances by ensuring the board thickness does not play into the geometry such that sides / top / bottom will still meet. Issue here is that I will need to fudge a bit on the placement of the interior pieces to ensure I don't inherit a bigger gap at the mouth than is advisable. Any imput here on how to fudge the interior pieces?

4. I'll be cutting down some of the larger piece with a circular saw. Any woodworking tips to ensure straight cuts / no tearout?

Answer all four questions correctly and you win an "I Helped Build Kofi's Kirishima!" T-shirt (cotton / poly blend; L or XL only).

Thanks in advance!
Kofi
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Old 29th December 2012, 01:30 PM   #2
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So long as the ply's void-free, it should do OK.

1/ Butt joints are as simple as it gets. I'm no woodworker, but FWIW, clamps. Lots of them.

2/ Yes. Incidentally, the most recent Fostex unit is the En. The eN label is what Dave used to employ for his modified E series units.

3/ Sort of. Start from the middle & work outward or you might find yourself with boards slightly shorter than intended & a bit of work to do with plastic-wood filler etc. A couple of mm extra termini area isn't something to get worried about.

4/ Take your time & make sure you've got a large level surface to work on is the message from this almost non-woodworker. If you can get someone to help, given the size of the pieces, so much the better. And invest in a quality blade if you haven't already. You'll probably blunt a cheap one half-way through cutting all the component parts.

Not asked, but: make very sure all the joints are square, and air-tight.

Last edited by Scottmoose; 29th December 2012 at 01:34 PM.
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Old 29th December 2012, 03:20 PM   #3
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Just got back from Lowe's and was horrified by the quality of the plywood. Voids, rotted pieces, peeling veneer, etc. I'll have to wait until I can get to the local hardwood place next week sometime.

Quote:
Originally Posted by Scottmoose View Post
2/ Yes. Incidentally, the most recent Fostex unit is the En. The eN label is what Dave used to employ for his modified E series units.
So, would the old 206E drivers be a poor match or would they work acceptably. Also, would either the En stock or Dave's eN be the better choice.

Thanks for the reply!
Kofi
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Old 29th December 2012, 04:06 PM   #4
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Quote:
So, would the old 206E drivers be a poor match or would they work acceptably.
Yes, they will work.

Quote:
Also, would either the En stock or Dave's eN be the better choice
I haven't heard one of the current En drivers modified in that way, so I can't pass comment on that front -none worth reading at any event. What I can say is that Dave's modifications addressed some of the issues the old E model had and I preferred it: some people liked the rawer sound of the stock unit though, so YMMV. Since you've already got a pair of 206s, you could always modify them yourself should you feel inclined. Phase plugs would probably be my first port of call, after which you could start to look at targeting specific regions on the cone where there is an obvious shift in the resonant behaviour.

Last edited by Scottmoose; 29th December 2012 at 04:09 PM.
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