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Old 23rd January 2013, 09:59 AM   #461
kambule is offline kambule  Hong Kong
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Default xrk 20 inch speaker plan

Your work and contribution are very impressive. I plan to build a 20 inch speaker with Vifa TC9FD. Noting that you have changed the throat width, would you mind to share a print of your 20 inch plan ?? I hope to get a successfuly reproduction. Thank you in advance.

By the way I have also gone through the other 100+ pages Foam Board thread and cant find your 20 inch plan as well. I only find the original sebastian and planet10 plans.
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Old 23rd January 2013, 12:56 PM   #462
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I'm with kambule also.
I've read till I got bug eyed and I don't see it. Would love to have a PDF or the like.
This thread has gotten me very intrigued, so want to try this!!!!
THANKS
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Old 23rd January 2013, 01:38 PM   #463
xrk971 is online now xrk971  United States
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Kambule and Ramzilla,
I am on travel this week and do not have access to the file of the photo of my plan. However, if you take a look at the photo of the completed channels, you may try to use that as a guide in drawing your plan. Post #45 in Foam Core Board Speaker Enclosures?

Click the image to open in full size.

I do not have a pdf as it is a large full scale hand drawn plan - you will get a photo from top view.

If you are itching to start, this should get you going. If I were to redo this, I would increase depth to 3 in.

Regards,
Xrk971
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Old 23rd January 2013, 02:38 PM   #464
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I have finally completed one of the Cornucopya horns for my Altec 405A drivers. Photos below of the build in-progress and the one finished speaker.

28” x 28” x 5” (channel depth). Using foam core for the back plate and 1/4” plywood for the baffle (which is really 3/16” thick, leaving one to ponder again about truth in advertising for wood products). To make the back plate, I spliced pieces of foam board together with paper and Mod Podge.

Initial attachment of channels with hot melt glue in the style of a caulk gun on one side, with the other side getting a line of wood glue to ensure firm attachment. Gorilla glue was applied to the edges of the channel foam boards; flipped over onto the baffle and weight applied with books until the urethane glue cured. Heavily stuffed with fiber fill behind the driver; lightly stuffed from the throat to the bifurcation in the horn.

There was room in the driver chamber for two of the driver mounting screws to be reinforced with small bits of wood on the back side, but not for the two others. So I used the old trick to strengthen the ‘threads’ in the thin wood baffle: drilled pilot holes, ran the screws in, removed them, then applied (thin, runny) super glue. Let the glue soak in & set up for a couple hours before mounting the drivers.

I didn’t bother with binding posts, just took an ice pick & put it through the back, ran the wire through, then sealed it with hot melt glue.

To hang the horn on a wall, I plan to use 3M’s Command Brand utility hooks. I suppose I could have glued a wood strip to the back & used regular picture hanging hardware, but this seems easier.

My wife’s comment upon seeing the horn placed on the mantle was: “That seems appropriate for this house.” (Understand that she knows it isn’t a long term placement.) On hearing the single completed horn she said, “Not Bad!” Her expectations were rather low for this foam board creation. After 41 years of marriage, she has expectations that any speaker worth listening to has considerable mass relative to its size.

I think they are somewhat anemic, probably due to Stiff Surround Syndrome (SSS). Less charitable folks might say they sound like Antique Surround Syndrome. Application of tone controls--cutting treble and boosting bass--results in a listenable, but unremarkable, sound. None the less, the sonic presentation is interesting. I will complete the second horn then decide on a further course of action.

I am debating the merits of pulling a driver from a previous build to see how it might work in this Cornucopya. Or should I just buy some new drivers? Would an FE103en work? (I am curious about this driver, as it has almost legendary status in Japan.) Been thinking I would like to sample those $12 Vifa drivers xrk favors too...

Cheers, Jim
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Last edited by Jim Shearer; 23rd January 2013 at 02:42 PM.
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Old 23rd January 2013, 08:29 PM   #465
kambule is offline kambule  Hong Kong
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[/QUOTE]
......
I do not have a pdf as it is a large full scale hand drawn plan - you will get a photo from top view.

Xrk971[/QUOTE]

thanks for your quick reply. Awaiting for the topview photo of 20 inch model.

If channel height is increased to 3 inches, should throat width be reduced to maintain the same throat area ??

kb
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Old 23rd January 2013, 09:01 PM   #466
xrk971 is online now xrk971  United States
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James Shearer,
Very nice work. The stuffing in the throats can really affect bass output, as can volume of driver chamber. An easy experiment is to reduce chamber volume by filling with foam peanuts, etc. You are lucky in that you used foam for back: you can take xacto and cut small windows to adjust stuffing in channel. You can seal by puttung foam window you just cut out with removable painters masking tape. Once happy, seal with hot melt. I suspect that removing some stuffing will improve bass. The 28 inch x 5 in deep design should have copious amounts of bass. Adding volume filler to chamber may increase upper cutoff frequency. Thanks for the update.
Good luck!
Xrk971

If you want to try Vifa's they need smaller cornu like 20 to 24 in. If you want to swap driver into what you have built, a solid 4 in class driver like MA CHR70 would be a low cost option.
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Old 23rd January 2013, 09:30 PM   #467
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Thanks xrk.

The problem appears to be the 405A drivers rather than the stuffing. With music that will make 4 to 4.5" Fostex drivers move way beyond Xmax the 405A don't show any significant movement. Still debating about pulling FE108eS from Mets and trying them. (And I did run them in for a couple days to loosen them up, as they have been sitting idle for a while.)

If (when) I get a pair of the Vifas, I expect to build either a Cornu or your cute little homage to FH3. Fun for winter time when it's too cold to go out doors and cut wood!

And thanks for the inspiration!

Jim
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Old 23rd January 2013, 10:23 PM   #468
xrk971 is online now xrk971  United States
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Jim,
Have you tried increasing power from amp sufficient to move those Altec cones? Glad to see you have an interest in the FH3-inspired design. Order the Vifa's by the half dozen, they are fun for trying on different projects without a lot of cost. My latest mltl with the Vifa's turned out really well. I might have to redo it in nice looking foam, right now it is a cardboard box. I am thinking of doing a flattened wall mount BIB next, Flatter is Better or FIB
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Old 24th January 2013, 02:48 PM   #469
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xrk,

Oh, I have plenty of power there to move those cones! They are on my LR system driven by a vintage Sansui 4000-- 45 wpc @8 ohms (and a big, heavy old style PS with plenty of reserves). More than enough to smoke the drivers if one were careless.

Eagerly awaiting a report on your FIB!

Cheers, Jim
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Old 25th January 2013, 12:58 AM   #470
xrk971 is online now xrk971  United States
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Jim Shearer,
What is an "LR" system? Anyhow, I agree 45 W at 8 ohms is plenty of power. I am planning on making the FIB soon but am trying to figure out whether to go with a single diagonal internal divider or an inverted "V" design. It should be a quick build in foam core though.
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