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Discussion Starter · #123 · (Edited)
Design will be approx 12-14 cuft, dual 21" opposed PR's with mms of 3530g.

I have some design details I'd like to square away first. One of the things is the curvature I'd like to use for the corners. I'd like to round this thing off a little more than is normal, still spitballing exactly how to do that, will change quite a bit depending on material. Sketch shows a double dato with triple walls and a 1.5" radius cut. Front face will have dowel pins to locate to second piece. I may be

The second thing is mounting. I have some concerns about box integrity with 15.5 lbs of moving mass between the two PR's per box, but I like doing things my own way anyhow. To that end I've devised a way to fasten the driver to the box using the box in compression and studs in tension. This will be a 4 part piece, can be installed after the box is made or retrofitted to an existing box easily. Will probably use aluminum for the base and it will be threaded for something like M8 or a little smaller studs. Initial design had each piece 89* (for a little float) but v2 of this design may engage a ship-lap type overlap between the pieces with some relief so fitment flexibility still exists but clamp load is as close to uniform as is needed. Just not sure what it'll cost to get these made. Will probably have a couple pilot holes to mount in place securely. This completely takes away the role of the wood of the box having to engage threads, and it's about a million times stronger than t-nuts, which I consider an overall stupid design (no offense to those who love them). This is a good very re-usable idea, but you would need different ones for different diameter drivers. I'm sizing this for the LaVoce San214.50's for first go around. I don't mind a minor machining out of the PR bolt holes, but it needs to be close. I'll post more about this as design matures.

You can probably tell there is a lot going on and the timeline will be long -will be lucky to have it all done this year, but that's ok, I'm having fun with it.

In the meantime I'll have 2 spare PR's, one Mach5 without extra mass and the PSI one. I'd like to keep the Mach5 as a spare but if anyone wants the PSI I'm happy to negotiate.


Chris
 

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Design will be approx 12-14 cuft, dual 21" opposed PR's with mms of 3530g.

I have some design details I'd like to square away first. One of the things is the curvature I'd like to use for the corners. I'd like to round this thing off a little more than is normal, still spitballing exactly how to do that, will change quite a bit depending on material. Sketch shows a double dato with triple walls and a 1.5" radius cut. Front face will have dowel pins to locate to second piece. I may be

The second thing is mounting. I have some concerns about box integrity with 15.5 lbs of moving mass between the two PR's per box, but I like doing things my own way anyhow. To that end I've devised a way to fasten the driver to the box using the box in compression and studs in tension. This will be a 4 part piece, can be installed after the box is made or retrofitted to an existing box easily. Will probably use aluminum for the base and it will be threaded for something like M8 or a little smaller studs. Initial design had each piece 89* (for a little float) but v2 of this design may engage a ship-lap type overlap between the pieces with some relief so fitment flexibility still exists but clamp load is as close to uniform as is needed. Just not sure what it'll cost to get these made. Will probably have a couple pilot holes to mount in place securely. This completely takes away the role of the wood of the box having to engage threads, and it's about a million times stronger than t-nuts, which I consider an overall stupid design (no offense to those who love them). This is a good very re-usable idea, but you would need different ones for different diameter drivers. I'm sizing this for the LaVoce San214.50's for first go around. I don't mind a minor machining out of the PR bolt holes, but it needs to be close. I'll post more about this as design matures.

You can probably tell there is a lot going on and the timeline will be long -will be lucky to have it all done this year, but that's ok, I'm having fun with it.

In the meantime I'll have 2 spare PR's, one Mach5 without extra mass and the PSI one. I'd like to keep the Mach5 as a spare but if anyone wants the PSI I'm happy to negotiate.


Chris

Google “Larry’s Rings” “Polk” “SDA”.... it’s been done and worked great.


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Discussion Starter · #125 · (Edited)
Yeah same basic idea as a t-nut, but implemented better (i.e. not relying on the wood to stop the t-nut from spinning) and distributing the clamping load much better. These will be much, much heavier duty than the rings mentioned, and will be 4 piece for easy installation. I'd rather just make the whole enclosure out of 1/2" aluminum (which has also been done) but don't have the funds or the forklift for 4 of those enclosures.

As long as people aren't stripping wood screws it's good! Thanks for sharing.
 

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Yup. In your case thicker would be warranted. Lots more pressure than in the SDAs.

I’d be interested in knowing costs when you get them machined...


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Discussion Starter · #127 ·
Preliminary maths says I should be able to get 3-4x+ clamping force of traditional methods. One will need to take care not to crack the frame.

Will update on costs.
 

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C.Pop's New & Improved 21" Mega Journey of Foolishness (with PR's)

Preliminary maths says I should be able to get 3-4x+ clamping force of traditional methods. One will need to take care not to crack the frame.

Will update on costs.

Sorry meant your metal should be thicker because your drivers will be under more pressure than SDA drivers :)....

The clamp force is obvious lol...

I’m using the same connectors (https://shop.stafast.com/sl14205h2130)
dgage is using for my subs but my next build will be using more pricey drivers...


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Design will be approx 12-14 cuft, dual 21" opposed PR's with mms of 3530g.
I haven't been around in quite a while so I too would like to say awesome build! I like your thinking on this design.

So does this mean that you are doing a LaVoce and PR on the front and back? Will this also provide any kind of loading benefit from the rear drivers and the wall behind it?

The second thing is mounting. I have some concerns about box integrity with 15.5 lbs of moving mass between the two PR's per box, but I like doing things my own way anyhow. To that end I've devised a way to fasten the driver to the box using the box in compression and studs in tension. This will be a 4 part piece, can be installed after the box is made or retrofitted to an existing box easily. Will probably use aluminum for the base and it will be threaded for something like M8 or a little smaller studs. Initial design had each piece 89* (for a little float) but v2 of this design may engage a ship-lap type overlap between the pieces with some relief so fitment flexibility still exists but clamp load is as close to uniform as is needed. Just not sure what it'll cost to get these made. Will probably have a couple pilot holes to mount in place securely. This completely takes away the role of the wood of the box having to engage threads, and it's about a million times stronger than t-nuts, which I consider an overall stupid design (no offense to those who love them). This is a good very re-usable idea, but you would need different ones for different diameter drivers. I'm sizing this for the LaVoce San214.50's for first go around. I don't mind a minor machining out of the PR bolt holes, but it needs to be close. I'll post more about this as design matures.
This may be a dumb idea, but since you are doing dual opposed on the PR's and the LaVoce's, I am going to assume that you are going to mount the drivers EXACTLY opposite of each other. If you made sure that the mounting holes were also directly across from each other, couldn't you just run a long piece of all-thread between the two drivers and then use nylock nuts on the outside to essentially clamp the drivers to each other? You can then determine what torque value to torque those nuts to. The nylock should stop the nut from loosening up but you could always take it a step further and drill a cotter pin hole into the all-thread. I think this could also be a form of bracing for the enclosure as well as the clamping would be external. It would also reduce cabinet weight while maximizing internal airspace compared to the normal wood bracing. Plus if you don't like the sight of the nuts and cotter pins, you can always build a beauty panel over the top of it to hide them. Just an idea I have been contemplating using for my next build.

Subscribed! Can't wait to see how this turns out! :D
 
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Discussion Starter · #130 ·
Not a dumb idea at all, and something I'll probably do a variant on, I just don't want to clamp the whole enclosure that hard. I've used nylock nuts often, they work well but for that application I'd probably just double-nut a couple standard nuts with a drop of red lock-tite.


Chris
 

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What if you had a 2x4 with a grove routed in to it for the all thread to go through. Then the pressure is on the 2x4 and not just on the enclosure? That is a lot of force and i could see it ripping things apart.
 

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I have some design details I'd like to square away first. One of the things is the curvature I'd like to use for the corners. I'd like to round this thing off a little more than is normal, still spitballing exactly how to do that, will change quite a bit depending on material. Sketch shows a double dato with triple walls and a 1.5" radius cut. Front face will have dowel pins to locate to second piece.

Wow, you can get any radius you want with interior corner blocks, and you you lose a lot of box volume to heavy wood, which isn't needed for motion control because of the opposed design..

You can get the required panel stiffness with dowels between opposite panels.


If you made sure that the mounting holes were also directly across from each other, couldn't you just run a long piece of all-thread between the two drivers and then use nylock nuts on the outside to essentially clamp the drivers to each other?
I was going to suggest the same thing, but using hardwood dowels; you can use long deck or lag screws that will each have hundreds of lb pullout capacity.

That removes the cosmetic concern with all-thread and nuts.

Not sure I get the concern with sufficient torque on the driver fasteners.
 

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Discussion Starter · #133 ·
Noah, I don't think you're fully realizing what 15lbs of moving mass will do over time. Dual opposed doesn't cancel force on the box itself, it cancels the box's propensity to walk around. Nevertheless, I was just sketching what different diameter roundings looked like on the enclosure. Don't sell the barn just yet. Plus I like flush mounting drivers. Sexy.

Lag bolts? LAG BOLTS?!?! What sort of heathen do you take me for? ;) In all seriousness, I like a bit of an industrial look. Maybe my time spent working for the navy's submarines, but I appreciate a proper bolting job. This thing is going to look awesome when it's done, but keep in mind I'm not the prettiest thing that graced this earth either so maybe birds of a feather....

P.S. It's immaterial, since either will get the job done for most applications, but a stud sized correctly for this would have thousands of pounds of clamping capability. If one has the means, steel is real.
 

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Let's call it 8 lb Mms, so 1 lb/fastener.

3 in. p-p at 18 Hz gives 50 g pk ( http://www.modalshop.com/vibration-calculator?ID=1036 ), so 50 lb/fastener; not sure how you came up with thousands of lb.

If you use the rod/dowel method, the box isn't in the load path, except for the regions in cyclic compression* between the rod and the fastener - inconsequential.

OK, I hear you on lag screws, but that's better than nuts.

Personally I'd use black oxide buttonhead socket screws; hardwood takes machine threads just fine.

* Wood dowels would presumably be larger in dia. than metal rods and give ample bearing area


Noah, I don't think you're fully realizing what 15lbs of moving mass will do over time. Dual opposed doesn't cancel force on the box itself, it cancels the box's propensity to walk around. Nevertheless, I was just sketching what different diameter roundings looked like on the enclosure. Don't sell the barn just yet. Plus I like flush mounting drivers. Sexy.

Lag bolts? LAG BOLTS?!?! What sort of heathen do you take me for? ;) In all seriousness, I like a bit of an industrial look. Maybe my time spent working for the navy's submarines, but I appreciate a proper bolting job. This thing is going to look awesome when it's done, but keep in mind I'm not the prettiest thing that graced this earth either so maybe birds of a feather....

P.S. It's immaterial, since either will get the job done for most applications, but a stud sized correctly for this would have thousands of pounds of clamping capability. If one has the means, steel is real.
 

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Discussion Starter · #135 ·
I didn't come up with thousands of lbs, that's a lot of silliness. When I said "sized correctly" I meant -literally fits in the larger holes of the big cast baskets, not "correctly" in the material capability avenue. We are saying the same thing.... steel in this application is huge overkill, but I like it. I am an MEE afterall.

The wooden dowel approach would definitely work and there is nothing wrong with it. I'm just not excited by it at this juncture. If I get my ass kicked by the quotes then it's my "still good but not as awesome" backup plan.

Isn't this all fun? TBH the hardest part for me is going to be the finish unless I wimp out and do duratex like I've been doing for the past 20 years. :rolleyes:

Chris
 

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... a stud sized correctly for this would have thousands of pounds of clamping capability.

Ah, *would* have, not required to have.

Unfortunately I have a special talent for applying the wrong interpretation where there's any possible ambiguity.

Yeah, finishing is a *****.

Seems like the project is 90% done, but the finish is another 80%.
 

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Discussion Starter · #137 ·
It's ok Noah, I'd buy you a beer any time. I suspected you were a math science or tech guy -are you?

As for the finish, at some point I may tap out and ask for help from some of my local resources. Have a great car painting guy but he seemed somewhat unwilling to goof around with huge subwoofer boxes.... can't imagine why....
 

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It's ok Noah, I'd buy you a beer any time. I suspected you were a math science or tech guy -are you?

As for the finish, at some point I may tap out and ask for help from some of my local resources. Have a great car painting guy but he seemed somewhat unwilling to goof around with huge subwoofer boxes.... can't imagine why....
Probably because he doesn't have a forklift? :p
 

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Discussion Starter · #140 ·
I knew it! hahaha

I'm about 20 years in, a dozen working for DoD on nuc submarines, last bunch at Honeywell Aerospace, project engineering mostly but specialize in testing. On the side I run a small fuel pump related business and do some work for an aftermarket turbocharger company. That's nearly (but not) enough to keep me out of trouble.

Current game: where to put braces
 

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