[subsonic1050]

Hey all - I don't have much experience in speaker building, so there are areas of building a speaker that I will need to rely on help from others (such as crossover assembly). What I have to offer is about 25 years of woodworking experience to hopefully add to the knowledge base out there.

I'm currently building 2 sets (4 total) triple servo subs. These call for 1" MDF for the baffle and 1.5" MDF for the walls of the cabinet. I hoped to just purchase some 1" and 1.5" MDF - but as you're probably aware there is a massive shortage right now. Therefore, I needed to laminate some .5" and .75" MDF together to achieve the desired thicknesses. This sounds simple enough, but if you just glue up some panels and slap some clamps on them you will run into problems. The center of the panels will not have the proper clamping force and you will have a bulging area in the middle of your panels that will cause all sorts of problems.

To solve this you can either use a vacuum bag and pump, or, use fasteners like screws spaced every 6" or so to pull the panels tight, OR if you don't have a vacuum press and don't want screw holes all over your panels you can use the method I will try to explain.

What I use are cambered cauls. A caul is simply a block of wood that spans across the item being clamped. The camber means that there is a curve on the caul on one side. You can see that this caul does not sit flat on my jointer - that is intentional. I use a hand plane and take staggered passes to achieve the curve. The amount of curve will depend on how long the cauls are and how thick and stiff they are.



You need several opposing pairs of these. The idea is that you position them so that the cambered side is facing towards your panels (curved side up on the bottom, curved side down on top). As you clamp the outside ends of the cauls, the curved portion of the caul will exert force on the middle of the panels where clamps would otherwise not reach.

Then simply apply glue to your panels - a glue roller is helpful to achieve an even amount of glue.



Then place the panels into the clamps with the cauls as described and shown. I am gluing up several panels at once (a nice advantage of this method). To keep the panels from shifting around I use a single small brad in 2 corners on each glue up.





After you get those cauls in place, you can even add some cambered cauls running in the opposite direction to ensure that enough clamping force is reaching the middle of the panel.



That's all there is to it! Just make sure you make your panels slightly oversized. Don't try to make them your final dimension right away. You will want to trim the sides off to reach your finished dimension.

Hope this helps somone!

-Brian

[glynnw]

Or simply have them wrapped.  Lacking your skills I recently had my Spatial Audio x5s wrapped in black for $200.  Looks great.

[S Clark]

Or simply have them wrapped.  Lacking your skills I recently had my Spatial Audio x5s wrapped in black for $200.  Looks great.

What you mean by this?  Wrapped in black _____??

[subsonic1050]

I'm not sure what you mean by that glynnw - this is not laminate - or veneer - this is laminating (combining) multiple sheets of MDF to make a thicker panel. It is structural to the speaker cabinet - not aesthetic.

[WGH]

I use Grizzly Glue for all my laminating. Grizzly is a polyurethane glue which has a much longer set time than yellow glue, important if you are doing a lot of panels at once. I like Grizzly better than Gorilla, it spreads better and is much cheaper plus the quality is excellent. Grizzly One is available on Amazon and through their website.
https://www.grizzlyglue.com/

Use clear plastic sheeting between panels in a multiple panel glue-up and clear packing tape (masking tape works too) on the cauls, glue won't stick to either plastic or tape.

If you are working on longer panels like for a tower speaker you will notice that even with a lot of cauls and a 3" thick platen on both sides of the panel you will still get ripples which is why professionals use a vacuum bag veneer press.

I've been doing woodworking professionally since 1981. Sold my building a couple of years ago and currently taking a break.
Plenty of laminating and veneering photos on my site if you poke around.
http://www.wghwoodworking.com/

[Sonicjoy]

Lacking a vacuum press, clamping caul's are nice and I have used them. However they are a lot of work to make (especially for a one off project) and you never seem to have the right size when you need them. I just stack the glued up panel's on strong flat surface like a cast iron table saw or solid workbench (or floor) and then use some leftover 3/4" plywood or MDF whatever you have on top of that to spread out the load (more layers are better) and then stack weight on top of the whole thing. Bricks, rocks heavy tool boxes whatever you have. You don't even need clamps. It is MUCH faster than messing around with all those clamps and caul's while your glue is starting to set up. That way you can use yellow wood glue with no worries, just use a piece of scrap wood to spread the glue quickly or a paint or glue brush.  Lot's of ways to do it. And yes sheets of plastic between panel's so they don't stick together helps if you are sloppy with the glue. And yes make your panel's oversize for gluing then cut to final size after because the layers will slip sideways and not be perfectly aligned while gluing up.

More tips from a finish carpenter.

[Sonicjoy]

Hey Subsonic1050, nice shop by the way! Love the Powermatic jointer.

My comments above are aimed at beginners or those that may not have a nice well equipped shop. There are many here that want to have Danny's awesome speakers but have little to no woodworking experience or tools, so I am trying to offer easy ways for them get started.

For those with dedicated shops, clamping cauls are a great addition to your clamping options for sure.     

[subsonic1050]

Good suggestions all around. Lots of ways to get the job done. I've never used polyurethane glue for laminating - that's a good suggestion. I use Titebond III and have never had an issue with it setting up before I'm in the clamps (when laminating - I definitely get glue anxiety with other projects!), and if I'm worried about it I use Titebond Extend but a longer working time is almost always welcome. I've also never run into issues with panels sticking to one another if I use a glue roller so that it isn't extremely messy. I don't know how you would glue a caul to the panels - there isn't glue near them, but if you're worried about that the tape works. I use tape on jigs used for thin strip laminations like for chair backs because you're going to get glue on the jig itself and that is a must in that situation.

I'm not a huge fan of stacking weight on top - here's why - it's almost impossible to have enough weight to achieve truly proper clamping pressure. For example, when you use a vacuum press you are essentially using atmospheric pressure to use as a clamp. That doesn't sound like much, but it's actually 14.7 psi. To put that in perspective, on the 14.5x41" panels I was gluing up here which will be trimmed down to make the sides of the servo subs, you'd need (14.5x41x14.7) = 8,739 pounds of weight stacked on top of those panels - evenly distributed - to achieve the same clamping force. Now in the example of cauls, in my example I'm using 10 parallel clamps - each with a clamping force of about 1500 pounds - so that's equal to 15,000 pounds of weight stacked on top. I'd still prefer the results from a vacuum press as that pressure is 100% evenly distributed - but in both cases you are achieving adequate clamping pressure. With weight - even if you were to stack 500 pounds on top (which would be hard to achieve in an area of that size) you don't even have 1 psi of clamping pressure. This will result in a panel with a glue line that is too thick. It will glue up, it will even be strong - but it won't be as strong or uniform as it could be. I'm sure you could, and sonicjoy you clearly have - used this method to good effect. I just think that unless you are short on clamps in your shop that one of the other 2 options is preferable - but that's just my opinion!

[subsonic1050]

Thanks sonicjoy! I love that jointer. Coincidentally, you can also make cambered cauls on a jointer if you're looking for a quick and dirty way to do it. I don't prefer that method because it really just makes a hump in the middle rather than a true curve, but it is fast if your primary concern is that it takes some time to make the cauls - which is a valid criticism. It is time consuming, but personally I'll take about any excuse to bust out the hand planes - I love planes so much I make my own wooden bodied planes and my iron planes almost never get used anymore.

[Sonicjoy]

What you said about clamping pressure is true. However I have found that the weight method works just fine. As long as the parts fit good it really does not take that much pressure. I used to worry about that also but not any more. I build high end custom homes for a living and efficiency of time is just as important as quality. I glue up things almost every day, building fancy trim, counter tops, mantles, cabinets, built in furniture, you name it.

No criticism intended, just an alternative idea. That's the thing with woodworking, there are so many different way to accomplish things.   

Hey I get it. When I'm doing my own projects without the pressure of the workplace, I love to slow down and do things the more traditional way. It is somehow more satisfying. I used to have access to a vacuum press so I have done it all the different ways, they all work.

Just my 2 cents.

[subsonic1050]

Totally get it sonicjoy - you're at least familiar with the advantages and disadvantages - other more inexperienced people may not be. My brother in law is a contractor, and I often tell him I couldn't do his job because I'm always in the pursuit of perfectionism. In the trades, you are often forced into a "this is good enough" type situation - otherwise you couldn't make any money! I expect that most people making these speakers are guys doing it on their own and a little bit of time isn't the end of the world. This could be a good thread for people to simply share how they have tackled their builds.

[MasterHiFi]

Just food for thought, it has been validated by multiple people that plywood, particularly two or more sheets glued together, make a stronger and more acoustically dead cabinet structure than MDF. I'll see if I can get some links that point this out, but I'd recommend this over MDF where possible. B&W is now using bent plywood in their matrixed Nautilus line of speakers, as are many other manufacturers these days. A thin coat of a rubberized material BETWEEN the sheets of plywood results in a virtually inert cabinet.

For bonding larger sheets together, if you don't have a workshop at your disposal, a quick and dirty method is to drill a hole or several, depending on the size you're bonding, and slide a bolt and some large washers through the hole(s), use a nut and large washers on the other side and tighten them down to bring the sheets together. You then can either plug the holes by tapping in a round dowel or slug with some glue, or plan to have the location end up as waste in your final design.

I realize this isn't the best method for everyone. I look at the amazing shop in the photos above with envy. My shop is my back yard. My work bench is two saw horses with a board in between. And my saw horses are two chairs facing each other. I'm just happy to have the yard. So for all those people out there like me who are flying by the seat of our pants, don't be afraid to get a little ghetto when you have to. What ever gets the job done.

I truly appreciate the education, subsonic1050. I will remember what you've said and pull it out of my back pocket when I'm in a bind. I just don't want the amateurs out there to be intimidated by the high level trade craft, though you obviously have such a command of this medium. I hope you'll continue to share your considerable experience with us.

Regards to all,
Dan

[subsonic1050]

Interesting MasterHifi - I had not heard that about plywood being more acoustically dead than MDF. That is surprising to me considering the construction of plywood. I would assume it would have to be a very high grade of plywood - like real baltic birch which doesn't have any voids in it. In general I don't like MDF as a material. It is considerably weaker than plywood, but I use it for situations where I need something nice and flat - or where I might need to paint the surface. I'm only using MDF for these servo subs because it seems to be generally accepted that MDF is a good, acoustically dead material to use.

Also - FOR SURE there are lots of ways to do this kind of stuff on the cheap. Really, a speaker cabinet is not something difficult to build. You could definitely do it in a backyard with a circular saw if you had to. The nice thing about the cauls is they don't cost any money if you have some scrap material around, but you will need some clamps. Having clamps is really a prerequisite for building speakers cabinets though, so I don't think there is anything more there. I suppose you would also benefit from having a hand plane or a jointer, but you can achieve the same curve on the cauls by using strips of thick tape - use large strips as a base and keep adding shorter and shorter strips centered on the caul until you essentially have a curve. Your quick and dirty method also works, as does simply using screws to pull the sheets together - just make sure you drill a pilot hole all the way through the first sheet so that the screw is only pulling on the bottom sheet. You could either leave the screws in (in something like the servo subs they would be covered by No Res anyway - or you could pull them out after the glue dries and fill the holes with a filler of your choice.

I certainly didn't intend to send the message that you need to have a shop to do this kind of stuff - I just wanted to share my method. It's been pretty extensively stated that there are many ways to skin this particular cat but I just figured I'd make a post about it as I hadn't seen anyone cover this topic.

[MasterHiFi]

Interesting MasterHifi - I had not heard that about plywood being more acoustically dead than MDF. That is surprising to me considering the construction of plywood. I would assume it would have to be a very high grade of plywood - like real baltic birch which doesn't have any voids in it. In general I don't like MDF as a material. It is considerably weaker than plywood, but I use it for situations where I need something nice and flat - or where I might need to paint the surface. I'm only using MDF for these servo subs because it seems to be generally accepted that MDF is a good, acoustically dead material to use.

Also - FOR SURE there are lots of ways to do this kind of stuff on the cheap. Really, a speaker cabinet is not something difficult to build. You could definitely do it in a backyard with a circular saw if you had to. The nice thing about the cauls is they don't cost any money if you have some scrap material around, but you will need some clamps. Having clamps is really a prerequisite for building speakers cabinets though, so I don't think there is anything more there. I suppose you would also benefit from having a hand plane or a jointer, but you can achieve the same curve on the cauls by using strips of thick tape - use large strips as a base and keep adding shorter and shorter strips centered on the caul until you essentially have a curve. Your quick and dirty method also works, as does simply using screws to pull the sheets together - just make sure you drill a pilot hole all the way through the first sheet so that the screw is only pulling on the bottom sheet. You could either leave the screws in (in something like the servo subs they would be covered by No Res anyway - or you could pull them out after the glue dries and fill the holes with a filler of your choice.

I certainly didn't intend to send the message that you need to have a shop to do this kind of stuff - I just wanted to share my method. It's been pretty extensively stated that there are many ways to skin this particular cat but I just figured I'd make a post about it as I hadn't seen anyone cover this topic.

Hi Sonic,

Yeah, I didn't know this about plywood either, and as far as I know this is something that has only recently come into vogue. The damping coefficient of plywood is actually slightly better than that of MDF, though only marginally so. But if bonding two sheets together, the application of a damping layer in between is highly effective. There are some other links out there that address plywood vs. MDF but I couldn't easily find them. Here is one useful link, though, and it includes some helpful demonstrations that back up the science. You'll want to start at 28:00 minutes in (before that is all about the theory of a Voigt tube speaker):

https://m.youtube.com/watch?v=EEh01PX-q9I

He also points out that the cheapest plywood still offers these benefits, which had me also scratching my head.

I think everyone should take a look at this video, it really altered my understanding of MDF. And assuming that most people are going to paint or laminate their build, there is no reason not to use the cheapest plywood available (unless you need to worry about things like humidity, etc.).

And yes, I think minimally everyone should have clamps on hand, a router, vibrating or random orbit sander, circular saw and drill at a minimum. I've already learned a lot from reading your thread about building the NX-Studios, like the recess you made to hide the platforms of the speaker stands, as well as other useful tips and tricks. Plus, I really like your idea about making a caul using tape! Who doesn't have a roll of duct tape laying around? If you do, pretend that you can't find it so you have an excuse to go to the hardware store... 

Dan

[subsonic1050]

MasterHifi - just want to be clear, I haven't previously built any NX-Studio's. I think maybe you are thinking of sonicjoy - who also posted on this thread. Two different "sonic's"! I do have on order 2 pairs of NX-treme's which I'll be building once the flat packs arrive from Jay, and in the meantime I'm working on 2 pairs of triple servo subs. I'm building one set for myself and one for a friend. I'll be veneering them in quartersawn teak.

I actually just watched that video recently. The gentlemen in those videos is clearly a very smart guy, but you can also tell he doesn't really know what good sound actually sounds like. He thinks some pieces of balsa wood with a $6 Dayton driver attached to the back give world class sound. While I haven't heard them in person I find that to be extremely unlikely. You can even somewhat tell in the Youtube video what it sounds like, despite his music choices being pretty poor. He does have some interesting scientific data to be sure, and I would certainly prefer to use plywood over MDF, which for the most part I try to avoid!

[WGH]

there is no reason not to use the cheapest plywood available

There is one reason: the cheapest plywood has internal voids. The only plywood I know of that doesn't have voids is architectural plywood and the Baltic birch plywood which is why both are expensive.

Here is a short video I made demonstrating the resonant properties if three popular speaker cabinet materials - Baltic Birch, Richlite, and MDF.
https://youtu.be/SkSxH40x5SA

Premium Combi-Core is ideal for veneering and painting because of the MDF top layer. Combi-Core also holds screws better than MDF.


Baltic Birch is available everywhere although 4x8 sheets may have to be special ordered

[subsonic1050]

WGH - that was exactly my thought as well. I can't imagine cheap plywood with voids would have better sound characteristics than a homogenous material like MDF.