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SME

(4) Sealed 21": Funk Audio UH-21v1

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Heh.  Such whimpy tweeters.  My horns are 15" wide:

 

 

 

 

Edit: Just to note, these subs will be going on each side of the rack, occupying the space currently taken up by the two Hsu Research subs (different models) and the tables that the front left/right sit on.  I may go a tad taller than the racks are (23 inches) but not by very much as I plan to use a retractable AT screen right in front of the TV and center channel and hope to be able to drop it as low as possible.

 

Discreet!

 

I bet your wife never even noticed you'd put them in place :P  lol  :lol:

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Sorry about the silence!  I got preoccupied with other things, namely more work on optimizing my front LCR.

 

It also has taken me a while to iterate through cabinet designs.  I didn't think it would be hard, but I am trying very hard to keep the weight down without skimping on bracing.  I think I'm about 95% there, far along enough that I started work today trimming my sheet stock.

 

The external dimensions will be 800 mm x 700 mm x 600mm (W x D x H) in a dual-opposed side-firing configuration.  The anticipated weight will be about 100 lbs without drivers and about 190 lbs with drivers.  My wife has already informed me that she will *not* be helping me move these.  The internal volume will come in at around 9.5 cuft or maybe closer to 9 cuft after accounting for the space occupied by the drivers.

 

Right now, I'm planning on using only one 3/4" layer of plywood on the baffles.  They will be mounted flush to the basket rim, leaves 3/8" of plywood actually under the drivers.  However each mount point will have a brace attached directly under it, and these braces will connect to the sides and top of bottom of the box as well as additional cross braces.  Even though it seems a bit weird to not double the baffles, I expect it will work out fine.  I am planning to separating the driver air chambers from one another.  This costs me about 6 lbs and 1/8th cuft volume, but gives me the option to run separate signals to them down the road.

 

I'm planning to cut dados into the front/rear and top/bottom panels for joining these panels to the bracing substructure and to use my Festool Domino to join the substructurere to itself and to the baffles.  I haven't decided yet whether to use rabbet/dado joining or Dominos between the outer panels.  I'd like to think the rabbet/dado style joining will seal better, but Dominos will probably be easier.  Either way, I should probably seal the seams using an appropriate product as a separate step.

 

It might be a few days before I finish the initial cuts.  I'm moving slowly.  The panels are a bit large for my workspace, and given the complexity of the design, I am doing my best to cut everything to the tightest possible tolerances.  If I succeed, it will make things a lot easier further down the road.

 

Edit: I still haven't solved my trim ring problem, but my best idea right now is to route each ring from plywood or MDF sheet attach it to the baffle, allowing it to overhang the outer rim of the driver.  The trouble is that I won't be able to make it more than 2" or so thick, and I expect that to be a big pain to route.  We'll see when we get there.

Edited by SME

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Be bold and CNC an aluminum trim ring out of 1/4" stock. Saves a lot of weight. Or are you trying to flush the surround with the baffle and have the driver deep inside the box?

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Be bold and CNC an aluminum trim ring out of 1/4" stock. Saves a lot of weight. Or are you trying to flush the surround with the baffle and have the driver deep inside the box?

 

Any suggestion as to where I could access a CNC machine to do this?  I'm also not sure how much I'll have to pay for four sheets of 1/4" thick 24"x24" aluminum or similar.

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I always outsource to a local shop. Should be a couple hundred max w/ anodizing --not cheap, but I personally love touches like that on subs. Makes them just a little more unique and special :)

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Be bold and CNC an aluminum trim ring out of 1/4" stock. Saves a lot of weight. Or are you trying to flush the surround with the baffle and have the driver deep inside the box?

 

The basket rim will be flush to the baffle with the surround sticking up about an inch.  The plywood/MDF ring would attach separately to the baffle, so added weight wouldn't be an issue.

 

 

I always outsource to a local shop. Should be a couple hundred max w/ anodizing --not cheap, but I personally love touches like that on subs. Makes them just a little more unique and special :)

 

Yeah that's pretty pricey when multiplied by 4.

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Have you seen Funk's snap in / bolt through trim rings on his subs? Maybe he would sell you a few if you asked.

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I actually originally ordered with trim rings, but was given the option to cancel and order the cheaper rubber ones instead.  Maybe I should reconsider having Funk make them, if he's still willing.

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Good looking drivers. Should be performers. Underhung drivers with 350 normalized motor force. LOL. :D

 

Nathan this is a bit off topic but did you start dressing the tinsel leads on the drivers using the CF cones? Just wondering.

 

Are they @ risk of shorting against the CFcones? Resin should provide enough insulation no?

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Are they @ risk of shorting against the CFcones? Resin should provide enough insulation no?

We did find under extreme conditions the leads would touch the cone, and we had thought the epoxy would insulate it enough *if the leads ever touched but we found it did not. Its not enough conductivity to actually "short" but it did enough conductivity to deteriorate the lead wire. The shrink tube over the leads makes them behave better anyway so it was a win win.

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I'm almost done cutting out the large pieces.  It took me a while, but I think I understand how to get repeatable results with my equipment now.  I'm ordering a new square and T-square from Woodpecker's because the square I've been using is not square enough.  I worked around the issue to get all my square cuts down to about 0.25 mm tolerance.  I just have a few more to do, and then I can start cutting out lots and lots of circles.  :)

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We did find under extreme conditions the leads would touch the cone, and we had thought the epoxy would insulate it enough *if the leads ever touched but we found it did not. Its not enough conductivity to actually "short" but it did enough conductivity to deteriorate the lead wire. The shrink tube over the leads makes them behave better anyway so it was a win win.

 

Oh is that's interesting, thanks for sharing. Ya the shrink probably adds some damping and whatnot too :)

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So are you getting the rings from Funk?

 

I think so, but I'll have to wait quite a while for them.

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Sorry for the lack of update.  I got distracted by other things.

 

I settled on design and dimensions and started cuts.  I am in the process of cutting lots and lots of circles.  I plan to order trim rings from Funk, but I have to wait for a while before I can order them.  The trim rings require double-layer baffles to look right, so I had to concede on that detail.

 

I'm still planning to do a matte black finish, but I'm kind of undecided as to whether to use Duratex with a fine nap roller and sanding or to use paint.  If using paint, I've seen some recommendations to use a spray paint, but I'm thinking Duratex will be more forgiving.  I also imagine I can apply Duratex indoors in my basement, which is certainly helpful this time of year when the weather is cold.

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Roller-Grade Duratex thinned with a little bit of water leaves a 'pebbled' or 'hammered' finish.  Without thinning, it can get quite sharp if you work it too much.

 

Make sure there is some ventilation in the basement, and wear an organic vapor respirator in a contained space like that.  Although water-based, it is not VOC free.

 

JSS

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Roller-Grade Duratex thinned with a little bit of water leaves a 'pebbled' or 'hammered' finish.  Without thinning, it can get quite sharp if you work it too much.

 

Make sure there is some ventilation in the basement, and wear an organic vapor respirator in a contained space like that.  Although water-based, it is not VOC free.

 

I saw suggestions elsewhere to use the spray-on product instead of the rolled-on product.  Any idea if this would work well instead of thinning the rolled-on stuff?

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Wow, those drivers look pretty nice. I wanted to model them in WinISD but I can't find the sensitivity of those drivers. Do you happen to know?

 

Definitely keeping an eye on this project.  :)

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Never tried the spray-on.  But odds are it is the roll-on with an added thinner and flow agent.  I also can't remember how much water I used, but I used distilled water and I tried several test panels before the real deal.

 

JSS

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I've always rolled Duratex on undiluted and never really cared about the finish, other than toughness, since they'd be getting road abused. I'm not much help.

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As a duratex alternative for cabinets that won't see any abuse, I've sprayed exterior latex through an undercoat or bedliner gun with reasonably good results. No thinning, water cleanup, super fast, and no vapor issues. It takes longer to clean the gun than to spray multiple small cabinets. I set the cabinet on a lazy susan in my makeshift blue-tarp spray-booth, then shoot it from about a foot or two away, about the same approach as texturing drywall. Lower air pressure means bigger splatters. I'd recommend a minimum of two coats, let it dry at least 4 hours between.

 

The result is a nice pebbled texture, no brush marks or roller tracks, in whatever color and sheen you chose. Not a lot of spraying skill required either. 

 

I'd attach a picture, but the Internets won't allow that. Here's a link:

 

https://goo.gl/photos/PrtEwLpMb8KjPkr56

 

Some day I will try Duratex.

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I decided to buy a gallon of sprayer grade Duratex.  I expect I'll have to experiment with rollers to find a texture that's to my liking.

 

I finally have some momentum on building these cabinets.  I finished cutting all my circles (all 12) and have glued doubled panels for all four front baffles.  Next I will be routing a lot of dados and rabbets.

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