Bracing Conversation

[ryanosaur]

As I'm still (very slowly) working on my Subwoofer plans, I've been researching Bracing. Admittedly, a flat pack would be sweet just to not have to figure this out...
But where's the fun in that?
I know that it is recommended to brace every 10-12".
I have seen @Matthew J Poes and others elsewhere comment that Window Braces are an inefficient use of space and are unnecessarily heavy, as well. One source of the web went so far as to argue that corners don't need bracing at all as this only serves to waste material and further add weight.

So where does this leave us?

• Dowels, strategically placed to maintain a 10-12" spacing? IIRC, Poes suggested he would do this approach if he ever built another Sub Cabinet (Did you? )
• Turning the Window Brace 45º so that it contacts the Rear and Side panels in their respective centers? I like this approach in that you can make a V-shape or 3-sided triangular brace specific to the cabinet dimensions, though requiring more material to cut out of the sheet stock and likely increasing waste.
• Hybrid approach? You could follow this concept with scrap material from the panel you are working from, cut straight pieces to length and brace much the way you could with dowels: diagonally from center-left to center-back/center-back to center-right, side to side... same with top-bottom bracing, including rear panel contact as well.

Moreover, using Construction Adhesive like Loctite PL3 would allow for some dampening action of its own as the Poly-adhesives are known to maintain some flexibility rather than harden to brittle much as your standard wood glues do.
Thoughts?

Cheers, all!

 

[Pogre]

Ha ha! I thought this was a steam vent thread about an antagonistic conversation you may have recently had with someone! "It was a bracing conversation!" Lol

 

[ryanosaur]

@TLS Guy
In a TQWT/Transmission Line build as we have discussed before (tapered large closed end to open narrow end), would the rule of bracing still apply if the CSA at the larger end big enough to warrant Bracing?
I presume, if so, a dowel would be enough to stiffen the panels there while minimizing the impact of taking away volume from the line?

IIRC, smaller lines don't usually require Braces as the fold (partition) serves that purpose in the cabinet?

Likewise, I've seen mention of using small dowels to create a support structure to stabilize the stuffing and prevent it from settling. Thoughts?

Thank you!

 

[lovinthehd]

Went with a combo of window bracing and some diagonal bracing (using leftover ply pieces) myself, just trying to use the materials on hand. Thought about bracing with dowels but that meant more material sourcing....

 

[ryanosaur]

Went with a combo of window bracing and some diagonal bracing (using leftover ply pieces) myself, just trying to use the materials on hand. Thought about bracing with dowels but that meant more material sourcing....

Hence my idea of replacing dowels with the Hybrid approach of using some straight cut scrap from the sheet stock already on-hand.
Admittedly, I question if MDF would be good as dowel-replacement between two opposing sides (if it is sturdy enough on its own as a .75x1.5" bar, for example)?

Ideally I would go to Baltic Birch for Sub Cabinets, but currently the 18mm sheets are still over $100 per. I would not question the Ply for a situation like that, in fact, I suspect you could get away with a narrower piece. Thoughts?

 

[lovinthehd]

Hence my idea of replacing dowels with the Hybrid approach of using some straight cut scrap from the sheet stock already on-hand.
Admittedly, I question if MDF would be good as dowel-replacement between two opposing sides (if it is sturdy enough on its own as a .75x1.5" bar, for example)?

Ideally I would go to Baltic Birch for Sub Cabinets, but currently the 18mm sheets are still over $100 per. I would not question the Ply for a situation like that, in fact, I suspect you could get away with a narrower piece. Thoughts?

Yeah I went with ply (BB and some 4x8 "birch" ply too, depending what was available). Made me look up what I paid last for BB, $42/sheet (5x5) in late '19. Never gave mdf much thought, particularly for bracing, tho.

 

[highfigh]

Hence my idea of replacing dowels with the Hybrid approach of using some straight cut scrap from the sheet stock already on-hand.
Admittedly, I question if MDF would be good as dowel-replacement between two opposing sides (if it is sturdy enough on its own as a .75x1.5" bar, for example)?

Ideally I would go to Baltic Birch for Sub Cabinets, but currently the 18mm sheets are still over $100 per. I would not question the Ply for a situation like that, in fact, I suspect you could get away with a narrower piece. Thoughts?

Find a panel of some kind that resonates when you thump it, then push one finger into the middle of the area that resonates most. You'll notice that most of the resonance stoops and it works the same way for the panels of a box- if you position the brace at the midpoint in any direction, you will cut the wavelength in half, which doubles the resonant frequency. If you divide the speed of sound by the panel length, you'll find the resonant frequency in that direction. You don't need to worry about the shortest dimensions but if the panels are long, you want to make them more rigid. Because air is causing the panels to flex to whatever degree it can, you could just attach a piece of material that's square, rectangular, circular or almost any other shape in the center of the open part of the largest panels and its mas will resist the resonance. Dowels work just like your finger and you can use the construction adhesive to attach them- one end can be left as a square cut, the other end can be shaped to allow getting it in place without the edge interfering.

 

[TheWarrior]

As I'm still (very slowly) working on my Subwoofer plans, I've been researching Bracing. Admittedly, a flat pack would be sweet just to not have to figure this out...
But where's the fun in that?
I know that it is recommended to brace every 10-12".
I have seen @Matthew J Poes and others elsewhere comment that Window Braces are an inefficient use of space and are unnecessarily heavy, as well. One source of the web went so far as to argue that corners don't need bracing at all as this only serves to waste material and further add weight.

So where does this leave us?

• Dowels, strategically placed to maintain a 10-12" spacing? IIRC, Poes suggested he would do this approach if he ever built another Sub Cabinet (Did you? )
• Turning the Window Brace 45º so that it contacts the Rear and Side panels in their respective centers? I like this approach in that you can make a V-shape or 3-sided triangular brace specific to the cabinet dimensions, though requiring more material to cut out of the sheet stock and likely increasing waste.
• Hybrid approach? You could follow this concept with scrap material from the panel you are working from, cut straight pieces to length and brace much the way you could with dowels: diagonally from center-left to center-back/center-back to center-right, side to side... same with top-bottom bracing, including rear panel contact as well.

Moreover, using Construction Adhesive like Loctite PL3 would allow for some dampening action of its own as the Poly-adhesives are known to maintain some flexibility rather than harden to brittle much as your standard wood glues do.
Thoughts?

Cheers, all!

I think the style of bracing as well as the spacing is really dependent on what the box size and shape is. If its ported, you need room for that. If the Helmholtz math allows for a slot port, then that is built in bracing for a portion of the box.

I would not think of adhesive for its sound damping qualities, if it allows flex then your structure cannot be rigid. That alone can 'muddy' the bass. Remember, you want it to be 'chocolatey'!

Price should be your determining factor for substrate. As long as it's a wood product, you can manipulate it pretty easily and glue it too. I like Titebond 3 because of water cleanup, and the joint is waterproofed as well once it dries. But it sets up very fast so you have to move quick.

 

[highfigh]

I think the style of bracing as well as the spacing is really dependent on what the box size and shape is. If its ported, you need room for that. If the Helmholtz math allows for a slot port, then that is built in bracing for a portion of the box.

I would not think of adhesive for its sound damping qualities, if it allows flex then your structure cannot be rigid. That alone can 'muddy' the bass. Remember, you want it to be 'chocolatey'!

Price should be your determining factor for substrate. As long as it's a wood product, you can manipulate it pretty easily and glue it too. I like Titebond 3 because of water cleanup, and the joint is waterproofed as well once it dries. But it sets up very fast so you have to move quick.

Some construction adhesives set rigid, because they need to but if the material (like a dowel) is forced into the space, it's not really necessary for it to be rigid, it just needs to stick.

 

[ryanosaur]

On the move right now, but I did want to say the same thing... these construction adhesives are very strong and rigid, but still maintain some flex. My understanding is this actually increases it's strength as an adhesive because a firm-dry and brittle adhesive can actually break under more extreme situations.

 

[highfigh]

On the move right now, but I did want to say the same thing... these construction adhesives are very strong and rigid, but still maintain some flex. My understanding is this actually increases it's strength as an adhesive because a firm-dry and brittle adhesive can actually break under more extreme situations.

PL6000?

Go to about :35 into the video-

 

[ryanosaur]

PL6000?

Pl 3X, linked in the OP.

 

[TLS Guy]

@TLS Guy
In a TQWT/Transmission Line build as we have discussed before (tapered large closed end to open narrow end), would the rule of bracing still apply if the CSA at the larger end big enough to warrant Bracing?
I presume, if so, a dowel would be enough to stiffen the panels there while minimizing the impact of taking away volume from the line?

IIRC, smaller lines don't usually require Braces as the fold (partition) serves that purpose in the cabinet?

Likewise, I've seen mention of using small dowels to create a support structure to stabilize the stuffing and prevent it from settling. Thoughts?

Thank you!

Because of the internal folds, TLs tend to be self bracing. If the TL is wide like the bass lines in my LR main speakers, then I add a central brace the length of the line.

Central brace.

Lots of screws into the back.

 

[highfigh]

Pl 3X, linked in the OP.

I helped a friend move and when I removed the fire extinguisher from the basement wall, he told me to leave the hanger. I asked why and he said there's no way it would come off because he had used PL 600, which was about the strongest at the time. I hit it with a hammer and it didn't budge.

 

[ryanosaur]

Re: Adhesives
I watched several build videos and perused many build threads earlier this year. Various flat packs and different designs, all with the intention of learning more about actual design, assembly process and learning from other's mistakes.
There really is two schools and I don't necessarily think that one adhesive is absolutely better than the other. Wood Glue is probably easier to use, but can be messy (as evidenced by the runs and drips (inside and out) on all the builds I've seen, including a common thought that if it isn't gushing out when you clamp pieces together, you didn't use enough!). Yes, it's easier to clean up (water when fresh) and it sands easily.
The flipside is the people using the Construction Adhesives with PL3X seemingly the preferred. Liquid Nails I think is a little more fluid and can be messier compared to a more pasty consistency of PL3X (also LN takes longer to dry and cure, and is a weaker bond). Above that, the PL3X is suitable for filling gaps which means if you get a good consistent bead, it should seal very well with no need to go over it repeatedly with free glue the way I've seen people do. Lastly, is the aspect of it's flexibility as a component of its strength as an adhesive in resisting breaking apart through shock, as well as it's potential to also dampen vibration from being conducted directly through to other panels.
The downside of the PL3X is that it is much more difficult to deal with cleaning up. It contains petroleum distillates which indicate needing a good solvent to break down when fresh. It resists sanding when dry, and any excess is best left to dry and cut away by knife prior to finishing.
Neither wood glue nor construction adhesive can be stained over without seeing it through the finish, so paint or veneer is still ideal if you are messy in application and care about the final appearance.

This is what I have gathered this past year, both watching and reading, as well as working with both in a more crude fashion. I have yet to assemble a Speaker or Sub Cabinet.

 

[lovinthehd]

Wood glue from Elmer's I got a good deal on in quantity, works fine.

 

[TheWarrior]

This is what I have gathered this past year, both watching and reading, as well as working with both in a more crude fashion. I have yet to assemble a Speaker or Sub Cabinet.

This.

You're obsessing over details that are relatively insignificant to the end result of a functioning subwoofer. A well glued, clamped and cured joint should be stronger than the wood itself. Just wipe up the excess after clamping.

Have you figured out what driver and amp you will be using? Room modes mean that one sub may serve one seat well, but get inconsistent results at other seats, meaning multiple subs should be made. And that's the big benefit of DIY is the cost savings. Duh.

Have you considered doing passive subs, so you can have an amp in your rack to power the subs, and then only need to run speaker cable to the locations?

 

[TLS Guy]

Re: Adhesives
I watched several build videos and perused many build threads earlier this year. Various flat packs and different designs, all with the intention of learning more about actual design, assembly process and learning from other's mistakes.
There really is two schools and I don't necessarily think that one adhesive is absolutely better than the other. Wood Glue is probably easier to use, but can be messy (as evidenced by the runs and drips (inside and out) on all the builds I've seen, including a common thought that if it isn't gushing out when you clamp pieces together, you didn't use enough!). Yes, it's easier to clean up (water when fresh) and it sands easily.
The flipside is the people using the Construction Adhesives with PL3X seemingly the preferred. Liquid Nails I think is a little more fluid and can be messier compared to a more pasty consistency of PL3X (also LN takes longer to dry and cure, and is a weaker bond). Above that, the PL3X is suitable for filling gaps which means if you get a good consistent bead, it should seal very well with no need to go over it repeatedly with free glue the way I've seen people do. Lastly, is the aspect of it's flexibility as a component of its strength as an adhesive in resisting breaking apart through shock, as well as it's potential to also dampen vibration from being conducted directly through to other panels.
The downside of the PL3X is that it is much more difficult to deal with cleaning up. It contains petroleum distillates which indicate needing a good solvent to break down when fresh. It resists sanding when dry, and any excess is best left to dry and cut away by knife prior to finishing.
Neither wood glue nor construction adhesive can be stained over without seeing it through the finish, so paint or veneer is still ideal if you are messy in application and care about the final appearance.

This is what I have gathered this past year, both watching and reading, as well as working with both in a more crude fashion. I have yet to assemble a Speaker or Sub Cabinet.

Don't listen to nonsense. Use wood glue, but use the yellow stuff and not the white. Do not use butt joints, for speakers. Dado the joints. If you do that a plan carefully you can use pre veneered wood. That saves a pot of time, expense and the veneer will not lift. You can get pre veneered plywood and particle board.

 

[highfigh]

Lots of good ways to join the panels- rabbets and dados are preferred, but butt joints will work if you add cleats in the corners and use mechanical fasteners (screws are best, followed by glue coated staples or finish nails. Brads work, but are really too small. Mitering the corners is difficult and inaccurate (not straight or even) unless the right machines are used ($$$$$). If you have the ability, rabbets and dados aren't difficult using a router and straightedge with good clamps. It's best to make the cuts and do the glue up without much delay- if the humidity increases, you could need to recut or sand some pieces in order to get them to fit.

Wood glue, specifically TiteBond II, is one of the best choices because it is a bit flexible and that means the joints won't fracture. If you're using plywood, use dado and rabbet joints, but if you use screws, pre-drill the holes with a bit like the one in the link-

Insty-Bit Wood Screw Countersink/Pilot Hole Drill Bits

Countersink portion extends along the pilot bit to provide clearance for a thicker, unthreaded shank—perfect for traditional wood screws.

www.rockler.com

You can use the same method if you use MDF, HDF (high density fiberboard) or anything else and if you want to make life easier, get some gluing clamps- I have built literally hundreds of sub boxes with the type in the link and they're small, but they work great. They can be used to butt one panel into the face of another panel, too.

https://www.lowes.com/pd/Pony-3-in-9100series-Corner-Clamp/1000989038?cm_mmc=shp-_-c-_-prd-_-tol-_-bng-_-PLA_TOL_216_Construction-Hand-Tools-_-1000989038-_-0-_-0-_-0&msclkid=d8fc27dd9da41da560cf464c828f3789&gclid=d8fc27dd9da41da560cf464c828f3789&gclsrc=3p.ds

As far as veneering, there are many ways to do that- the most difficult is using wood glue, but there are ways to make it easier- woodworking forums have discussions about this and one method involves applying it to the veneer and substrate using a roller to make the coating as even as possible, letting it skin over to the point where it's almost dry and using a clothes iron to make the glue on both surfaces stick. No steam- that will screw up the veneer.

You can also buy pre-glued veneer- the glue is a type of hot glue and this also uses an iron to make it stick. You can also buy glue sheets, cut them to size and sandwich this between the veneer and substrate. If you want to make the corners stand out, you don't need to worry as much about perfect veneer cuts- use a rabbeting bit in a router, make the cuts on the corners and glue a strip of wood or some other material (could be almost anything, really), using a flush cut bit and sanding to make the corners the way you want- could be square corners, rounded or chamfered or some other profile.

 

[ryanosaur]

Eek!
I thought the adhesive would be an interesting side conversation to bracing. Didn’t mean to stir the pot.

For the record, I value these discussions. It is easy to learn a lot from bringing different people and their views together. I've seen a lot of conversation that is focused exclusively on the wrong details, and I know I've been guilty of it too. As always, my gratitude for participating; sharing! Thank you,

Since it was brought up, I am planning for multiple passive (most likely) subs. Depending on how my designs come together, I have 6 drivers to work with and am expecting to use 3 finished Subs in my main room, be they single or dual driver.
Amps are problematic in that they are sold out: two models of Crowns (XLS2502, XTI4002), even Behringers, etc. I’m also talking to a person about using Hypex modules to build Amps for me. On the other end of that conversation is Speaker Power, however their Amps are priced somewhat prohibitively to me. Not saying I can’t afford them in the long game, but that’s aside the point.

I am set up for dado and rabbet construction. I have a very good router and table. I already have a collection of bar and pipe clamps, and will be using a Brad Nailer to help stabilize the joints while whichever adhesive sets.
I will be using a double thickness baffle.

If screws become necessary, I have a countersink bit similar to what was linked above.

While material costs are still high, I am looking at MDF to build a 4cu.ft sealed and a 10cu.ft vented cabinet. Mainly, I want to test the performance between the two and see how they behave in my room. I’m hoping with a little more time, Baltic Birch will come down some more in cost… and perhaps Amps will be available again by then.

My pace is slow and deliberate. I tend to be like that when I am learning something new. Probably instilled in me by my Dad, an engineer (EE, working for defense contractor straight out of school during the late ‘60s).
I did pretty good in jr high wood shop, but that was a long time ago. More recently, I dusted off some very rudimentary drafting and architectural skills and built our own greenhouse. I’ve also done some basic items like raised garden beds, work bench, utility table, workroom tables, as well a few specialty projects requiring a little more finesse. I know how to and can frame a wall and have built and installed two false walls for a project I was recently doing for an acquaintance (one of which can be taken down with almost no sign of it having been there in the first place; a request he made (I used Liquid Nails Heavy Duty for the sill plate on concrete because it was suggested in a few places that a good whack with a Sledge Hammer could knock it free whereas the Poly Adhesives require much more effort and would likely require prying to dislodge through destruction of the wood. He did not want to drill and use concrete screws... (I digress ))).

These Sub cabinets will be my first foray into “fine” cabinet making.

Finishing will be another thread altogether.

Back to regularly scheduled programming.

*note: I say "passive, most likely..." I am not going to install a plate amp at all. I have not seen any affordable Plate Amps that will do what I require. I have considered when I build the finished cabinets to include a compartment where I could Rack Mount an amp unit directly in the cabinet. This would only be the case if I were to be able to acquire the Hypex Modules I am considering as a dark horse option. The Amp chassis would be designed so that the "face" is the business end of the Amp with all connection points and switches, thus allowing for easy connection from whatever DSP solution I use to manage the drivers, and the cabinet itself would still have Neutrik SpeakONs to plug into.
As the conversation with the Amp Guy unfolds, I will share if there is anything worthwhile.