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Old 3rd January 2019, 05:39 AM   #1
jdrouin is offline jdrouin  United States
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Join Date: Feb 2012
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Default CGR mFonken103Sol

I'm part way through a build of the Classic Golden Ratio Fonken for FE103Sol. Tomorrow I'll cut the internal brace holes and will then apply damping material (wool batting) to the interior walls.

Should damping material go on the front baffle? In the Baby Labs plans it doesn't, but this one has more surface area and the instructions give no particulars on that.

Also, for the thinner polyester batting that goes on the center side of the brace, should I cut it out where the holes are or just lay it over the whole thing, covering the holes? There was some debate about that in a fonken build thread involving Chris but I can't find it right now.
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Old 6th January 2019, 05:27 PM   #2
jdrouin is offline jdrouin  United States
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Managed to cut the brace holes and driver cutouts yesterday, and will glue the brace today. Using a jigsaw, I was unable to fit the cutouts exactly to the back of the driver, so I'll have to insert paper shims.

The holes are 1", 2 1/4", and 3 1/2", cut with a router and circle jig, following the plan as close as possible. Would there be any advantage with a roundover on the hole edges (or at least those that are far enough apart)?

Also, I plan to line the interior front baffle with wool batting, unless you think that's too much.

The CGR build has already been good practice for the trapezoidal mFonken.
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Old 6th January 2019, 07:19 PM   #3
planet10 is offline planet10  Canada
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CGR mFonken103Sol
I’m watching and will be pinching your pictures.

Yes, dsmping on the baffle (but not such that it gets in the way of the back of the driver). Do not cut out the holes in the damping on the holey braces. It is over the holes that we really want it — the peak of any side-to-side standing wave is in the exact centre, so the most effective place for the damping is right there.

dave
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Old 6th January 2019, 10:11 PM   #4
jdrouin is offline jdrouin  United States
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Gotcha! Thanks. Aiming to have two skeletons assembled and panels damped by the end of the week.
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Old 11th January 2019, 04:30 PM   #5
jdrouin is offline jdrouin  United States
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I glued the baffle, shelf, brace, and one side of the second speaker, and then fitted paper shims to each brace.

For each shim, I cut a piece of computer printer paper 3 3/4" wide to allow for up to six folds that match the 5/8" brace thickness, and 3" long to more-than-cover the contact length of the back of the driver. I then placed them on the brace and slid in the drivers, removing one fold-layer at a time until the bezel met flush with the baffle and had a tight enough pressure on the paper to make it difficult to pull out. One enclosure required five fold-layers and the other only two because of the slight variations in my hand-cut diver cutouts (I have allocated a specific driver to each enclosure for consistency, just in case).

When I make the driver cutouts in the brace of the mFonken103SolT, I'll be sure to clamp on a fence to guide the jigsaw, to ensure a good parallel contact with the back of the driver. Though it appears what I've done for the CGR will work fine.

Question: I have the foam inserts for the driver bezels, but might it be worth putting Blu-Tak or some similar kind of putty in that groove near the circular opening of the bezel? (See my finger in attached pic.) I thought it might help to get an airtight seal and also tamp vibrations.
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Old 11th January 2019, 06:02 PM   #6
planet10 is offline planet10  Canada
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Quote:
Question: I have the foam inserts for the driver bezels, but might it be worth putting Blu-Tak or some similar kind of putty in that groove near the circular opening of the bezel?
Foam gaskets. We used to fill the cavity in the bezel with a liquid boat damping compound that turns hard. But once the driver is clamped tp the baffle there is only a really small difference and it was a lot of messy work to do it, so we quit. Ductsel or blueTac would not hurt, just not so much it imedes mounting the driver.

Remember: screws only so tight that the washer no longer spins. Screws are all too often too tight.

dave
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