Sub box construction question?

L

Loren Jones

Sophomore
Jun 25, 2011
155
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16
Hampton Roads VA
Hello DIY pro audio speaker cabinet builders.

I have a simple construction question. I am building a cabinet with multiple panels inside that are part of the cabinet design. These internal panels have been attached to the bottom of the cabinet with glue and pocket screws. I will do the same for the sides, baffle and rear of the cabinet. When I get ready to put the top on the cabinet I won't be able to get inside to put pocket hole screws in due to the design. How would you attach the top of the cabinet?

1) Just clamps and glue
2) Brad nails and glue
3) Glue plus screws through the top panel into the internal panels from outside

Basically I am wondering if just glue is strong enough. Baltic birch is the material. Use will be portable use but almost always in just one (church) building.

Thanks,
Loren Jones
 
Re: Sub box construction question?

I do all 3;

I put glue on the joint for strength, a good air seal, and to prevent cabinet rattle. Then I use an air powered brad nailer as I put the cabinet together because you can precisely line the edges of the joint up and tack them in place as you go along. Finally I use a countersink bit and drill a few pilot holes, just a couple per side of cabinet is usually fine, and use 1 1/4" coarse thread drywall screws to add extra strength and pull the joint together for a good glue bond. The screws also help keep the joint from splitting if the cabinet gets dropped. Finally fill the screw and nail holes with bondo, sand, and paint.
 
Re: Sub box construction question?

Loren Jones said:
Hello DIY pro audio speaker cabinet builders.

I have a simple construction question. I am building a cabinet with multiple panels inside that are part of the cabinet design. These internal panels have been attached to the bottom of the cabinet with glue and pocket screws. I will do the same for the sides, baffle and rear of the cabinet. When I get ready to put the top on the cabinet I won't be able to get inside to put pocket hole screws in due to the design. How would you attach the top of the cabinet?

1) Just clamps and glue
2) Brad nails and glue
3) Glue plus screws through the top panel into the internal panels from outside

Basically I am wondering if just glue is strong enough. Baltic birch is the material. Use will be portable use but almost always in just one (church) building.

Thanks,
Loren Jones
Click to expand...

The glue is always stronger than the wood, as long as good and accurate joinery methods are used. The fasteners just minimize the need for clamping and waiting for the glue to set. While pocket hole/screw fastening is nice, it was a lot of extra work that really wasn't needed. You could have butt jointed and nailed/stapled it all and been just fine. Occasionally a screw might be needed due to "real life"(some accumulation of errors over the course of assembly, wood decides to misbehave, etc.).

Best regards,

John
 
Re: Sub box construction question?

John Halliburton said:
The glue is always stronger than the wood, as long as good and accurate joinery methods are used. The fasteners just minimize the need for clamping and waiting for the glue to set. While pocket hole/screw fastening is nice, it was a lot of extra work that really wasn't needed. You could have butt jointed and nailed/stapled it all and been just fine. Occasionally a screw might be needed due to "real life"(some accumulation of errors over the course of assembly, wood decides to misbehave, etc.).

Best regards,

John
Click to expand...

Thanks John,

Yeah, I know the glue is strong if the joint is true. When I do woodworking things building furniture I completely trust the glue and try to avoid the need to use any mechanical fasteners. As far as the pocket hole screws they seemed the most convenient way to precisely position the various panels while the glue was setting up. I guess I have my answer there; I will be OK with just glue, especially for internal panels. The back/sides of the cabinet I will at least nail and probably will screw as well.

Loren
 
Re: Sub box construction question?

Tom Manchester said:
I do all 3;

I put glue on the joint for strength, a good air seal, and to prevent cabinet rattle. Then I use an air powered brad nailer as I put the cabinet together because you can precisely line the edges of the joint up and tack them in place as you go along. Finally I use a countersink bit and drill a few pilot holes, just a couple per side of cabinet is usually fine, and use 1 1/4" coarse thread drywall screws to add extra strength and pull the joint together for a good glue bond. The screws also help keep the joint from splitting if the cabinet gets dropped. Finally fill the screw and nail holes with bondo, sand, and paint.
Click to expand...

That is probably what I will do with the back and sides of the cabinet. The internal panels will be hard to mechanically fasten because I won't be able to see where they are, so I'll probably just rely on the glue there. I was just making sure there was no consensus that said I would be setting myself up for failure by relying on just glue for parts of the project.
 
I agree with John. A screw into the side of plywood is not adding much strength once the glue is set.

When I was doing a lot of cabinetry I always preferred biscuits on end joints.
 
Jay Barracato said:
I agree with John. A screw into the side of plywood is not adding much strength once the glue is set.

When I was doing a lot of cabinetry I always preferred biscuits on end joints.
Click to expand...

Just last week I repaired a loose baffle board on two EAW JF560z's. It was only glued across one section (added support for the horn meant there was more going on up top) and evidently over time it broke partially loose. The defect was hidden behind the grill but I could hear it at some frequencies. I used some special, low viscosity chair-joint repair adhesive that wicks into joints and nailed it back together as a quick repair.

Of course better initial construction - using biscuits or other joinery techniques - would have also solved the problem. So too would not moving the speaker repeatedly!


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Re: Sub box construction question?

Loren Jones said:
That would work and I will probably do that for a couple pieces right in the middle where the clamping pressure won't be as tight.
Click to expand...

I've built 16 LAB subwoofers among many other things. I used sheetrock screws and glue for the first 4, then decided it was just as effective to use brads and glue for the latter 12. In either case, use LOTS of clamps. I have an arsenal of the huge QuickGrips which work great. I use PL Premium for glue since it expands as it dries, and I only use butt joints.
 
Re: Sub box construction question?

Silas Pradetto said:
I've built 16 LAB subwoofers among many other things. I used sheetrock screws and glue for the first 4, then decided it was just as effective to use brads and glue for the latter 12. In either case, use LOTS of clamps. I have an arsenal of the huge QuickGrips which work great. I use PL Premium for glue since it expands as it dries, and I only use butt joints.
Click to expand...

Thanks Silas,

Excellent information born from experience. Your LAB subs I'm sure were used and moved around under much more strenuous circumstances than this cabinet will see at our church. I'm using Gorilla (polyurethane) Glue for the same reason. That way I don't feel the need to go caulk every joint.

Loren
 
Re: Sub box construction question?

I have heard people say to stick with regular woodworking glue as the gorilla glue expands. Have not used it myself so have no opinion but have had good results with the standard stuff.
 
Re: Sub box construction question?

Before building his LABs a friend did some destructive testing of glues. IIRC Gorilla Glue was less effective than good ole' Elmers Carpenters Glue. The most effective was West System Epoxy, which not only held the bits together, but soaked in and reinforced the plywood. (He also used the stuff as his outer coat - it's holding up well.)
 
Re: Sub box construction question?

Bennett Prescott said:
Go to one of the big cabinet shops and see what they're doing. It's good construction (big CNC routers means you have to cut fewer corners), regular wood glue (I prefer Titebond II) and some nails to hold it together while it cures.
Click to expand...

I would've stuck with regular wood glue if everything had been cut on big CNC routers rather than the Harbor Freight table saw I paid $100 for used. I know the line about a poor carpenter blaming his tools, but between whatever skills I am lacking and any margin for error in my equipment small inaccuracies when cutting precise angles meant that the slight wiggle room the expanding glue allowed was a welcome luxury come assembly time even though the final strength isn't as high. The last boxes I built were less complex and I used Titebond II on them.

This box is a done deal now. The top was attached with Poly glue, brads around the edges and a couple pocket screws from the inside through the driver cutout. Should hold together for the gentle use it will see at our church.

Loren
 
Re: Sub box construction question?

Tim Padrick said:
Before building his LABs a friend did some destructive testing of glues. IIRC Gorilla Glue was less effective than good ole' Elmers Carpenters Glue. The most effective was West System Epoxy, which not only held the bits together, but soaked in and reinforced the plywood. (He also used the stuff as his outer coat - it's holding up well.)
Click to expand...

Yeah, the West System Epoxy is very good stuff. I have used it on other furniture building projects. I feel like it is overkill (expense and hassle to work with) for most woodworking needs, but it definitely comes in handy sometimes.

Loren Jones
 
Re: Sub box construction question?

I stronglly disagree with the statement "The glue is stronger than the wood-therfore you don't need mechanical fasteners".

OK- yes the glue is stronger than the wood-BUT ONLY FOR ONE LAYER OF THE WOOD!!!!

Once that layer peals off-you are hosed. Like relying on something that "sticks to paint". You are only as strong as how well the paint sticks to the wall. You may not be able to seperate the item from the paint-but the paint can easily come off the wall. And if the paint is really attached to the drywall-then you are only as good as the paper on the drywall attached to the "rock" material. A nail or screw all the way through to the stud will hold up MUCH MUCH more!

I prefer glue AND lots of mechanical fasteners. Glue coated staples or large finish nails. Little brads are better than nothing-but not as good as long thick/strong fastener. That way when the fastener goes in-the glue around it melts and then reglues the fastener into place-a double "whammy".


The mechanical fasteners are for A LOT more than just holding the piece together while the glue dries.

When you start dropping cabinets and banging them around-the ones with glue and mechanical fasteners are the ones that are going to hold together longer.

Screws are nice-but are very time consuming and expensive. I usually use them only for special places in the cabinet.
 
Re: Sub box construction question?

Ivan Beaver said:
I prefer glue AND lots of mechanical fasteners. Glue coated staples or large finish nails. Little brads are better than nothing-but not as good as long thick/strong fastener. That way when the fastener goes in-the glue around it melts and then reglues the fastener into place-a double "whammy".
Click to expand...
I agree with all you said.

One addition, I have used biscuit joints, and had them fall apart because the biscuit expands and contracts at a different rate than the plywood in differing humidity. Here in the high desert the usual is around 22%, but can go to 80% for a short period after a rain.

Now, anyplace I'd have use a biscuit I use a pocket hole jig and screws.

Art
 
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