Carvin LS1503 Bracing

[lbwdog]

Last night I played another gig with my MarkBass LMTube 800 into my (3015LF modded) LS1503, and I'm happy to report that I'm still diggin' this combination. The venue is a mid-sized casino lounge and I don't go in the FOH.

I did notice after three songs, the amp had vibrated almost off the back of the cab, so I removed it from there completely. Then, because I wasn't feeling too well, I would sit on top of the cab during ballads, and WOW, noticed the vibration was "off the chart"!

Carvin uses minimal bracing in these cabs, so I'll be adding some bracing (at least across the top) when I can get a chance. Curious if anybody has done this?

[billfitzmaurice]

Originally Posted by lbwdog

Carvin uses minimal bracing in these cabs, so I'll be adding some bracing (at least across the top)

If by 'across the top' you mean a stiffening spar, that's the least effective bracing scheme. A single 1" dowel running from the top to bottom mid panel would be at least twice as effective.

[jnewmark]

Curiosity has got me here. What is the best way to attach a brace like this? Do you use just glue, or drill a little pilot hole on each end to snug the dowell in, then glue it into the holes?

[greenboy]

The spar in conjunction with other spars usually works better for me. It gives local damping as well as overall rigidity when used as part of a system. It as a system can also can be worked into the cutouts for handles and connector cups for their screw bite, and gives a lot of glue surface.

Anyway, regardless of opinion on all that, the dowel straight up and down isn't going to be optimized here: there's a shelf that goes right up to the pole-mount socket at the place where it would make sense to connect at the bottom if I recall.

[billfitzmaurice]

Originally Posted by jnewmark

Curiosity has got me here. What is the best way to attach a brace like this? Do you use just glue, or drill a little pilot hole on each end to snug the dowell in, then glue it into the holes?

Drill a 1/16" to 1/8" deep hole in each panel, cut the dowel a smidge longer than the panel to panel distance. Put a dab of PL adhesive in each hole, flex the dowel to snap it into place. The expanding PL will make everything tight and right. One dowel in the center of the panels is equivalent to doubling the panel thickness. Four, at 1/3 intervals fore and aft and front to back, equals quadrupling the panel thickness.

[lbwdog]

Greenboy, not sure how your reply got posted to another thread so I'll put it here.

(quote)
I forget whether you have the "cup" midrange chamber or the stronger plywood one that because of its build style also provides bracing to the top one side, and the baffle. Carvin had it so right, back then.

Anyway, check this out: http://greenboy.us/fEARful/bracing.htm - I figure either a 1.5" "stick running from front to back near the center of the top panel like in the pic there would do what you need.

and, my reply;

Yeah GB, I got mine shortly after you got yours and was surprised to find the chamber was the plastic cup.
Just recently, I mentioned how the cab resonated like a tom-tom when knocking on the top. When sitting on my cab Sat nite I couldn't believe how it vibrated my teeth on all the low notes! I can see where that 3015LF could destroy a flimsy cabinet in time! LOL!

I have some 1x2 sticks so I can cut one to where it fits snug from front to back, and glue it in. Maybe three or four screws too?

[lbwdog]

Originally Posted by billfitzmaurice

If by 'across the top' you mean a stiffening spar, that's the least effective bracing scheme. A single 1" dowel running from the top to bottom mid panel would be at least twice as effective.

Originally Posted by greenboy

Anyway, regardless of opinion on all that, the dowel straight up and down isn't going to be optimized here: there's a shelf that goes right up to the pole-mount socket at the place where it would make sense to connect at the bottom if I recall.

Yeah Bill, I don't think the dowel will work on this cab because of the port shelf and pole mount. Wouldn't be able to get it close to the center line. Sounds like a good idea otherwise.

[billfitzmaurice]

Originally Posted by lbwdog

Yeah Bill, I don't think the dowel will work on this cab because of the port shelf and pole mount.

It will if you do it like this:

[lbwdog]

Originally Posted by billfitzmaurice

It will if you do it like this:

Thanks, I'll check into that.

[greenboy]

As a system, that's nice, Bill; each dowel tied into at least two more, and with the verts sitting on shelf dividers which are part of an overarching plan.

[billfitzmaurice]

Originally Posted by greenboy

As a system, that's nice, Bill; each dowel tied into at least two more, and with the verts sitting on shelf dividers which are part of an overarching plan.

With 1" dowels they don't need to be tied together, as there are no lateral shear forces when the box is in compression mode, and they're only slight when it's in decompression mode. If you did tie the dowels together you could reduce their diameter to 1/2" with no ill effect, but that would require precisely locating the receiving holes in the cab walls so that they'd join well.

[Doug Parent]

Following this and I beg the forgiveness of the OP if I piggyback this thread with a similar query. I have a Carvin LS1501 single 15 Sub enclosure that has a shallow shelf port (17.5 wide X 1.75 high and the depth is only 4.5") ...as can be seen in the photo the internal bracing is minimal. I have two questions, using the dowel method I assume the port shelf is too shallow to bother incorporating any dowels, and that I should just dowel the center of the cabinet (top to bottom and side to side) ??

Also, I plan in using a 3015LF in this cabinet. Does the existing port area look anywhere near being correct or am I correct in thinking it needs to be deeper? The photo on the right is shot looking down into the cabinet and the horizontal shelf is shown inside the cabinet.

(20 X 19 X 22 is roughly the internal dimensions with the port area included)

[billfitzmaurice]

Originally Posted by Doug Parent

I have two questions, using the dowel method I assume the port shelf is too shallow to bother incorporating any dowels, and that I should just dowel the center of the cabinet (top to bottom and side to side) ??

There's no need to brace within at least six inches of the box corners. The corner is the strongest part of the cab, that's why corner cleats are a waste of lumber. You should brace in every direction, including front to rear.

Also, I plan in using a 3015LF in this cabinet. Does the existing port area look anywhere near being correct or am I correct in thinking it needs to be deeper? )

I can't tell from the pictures.

[Doug Parent]

Thanks, I like the dowel approach! Here's another pic of the port from another angle. The port is 17.5 wide X 1.75 high and the depth of the port shelf is 4.5". (The bottom of the port is the bottom panel of the cab)

There is a center partition in the port but I subtracted the width of it from the above data)

[Doug Parent]

Originally Posted by billfitzmaurice

Drill a 1/16" to 1/8" deep hole in each panel, cut the dowel a smidge longer than the panel to panel distance. Put a dab of PL adhesive in each hole, flex the dowel to snap it into place. The expanding PL will make everything tight and right. One dowel in the center of the panels is equivalent to doubling the panel thickness. Four, at 1/3 intervals fore and aft and front to back, equals quadrupling the panel thickness.

Bill do you mean drill a pilot hole that is the same diameter as the dowel?
What is "PL adhesive? PL?

[billfitzmaurice]

Originally Posted by Doug Parent

TThe port is 17.5 wide X 1.75 high and the depth of the port shelf is 4.5".

7 to 8 inches would be better.

What is "PL adhesive? PL?

The only thing one should use for cabinet building.
http://www.loctiteproducts.com/p/12/...n-Adhesive.htm

[Doug Parent]

7"-8".....thats more or less what I was going to guess. I think I can extend the existing shelf somehow. Unless you have another suggestion, I'm thinking glue some new cleats in place and screw an extender shelf to them.

[Greenman]

Originally Posted by Doug Parent

Bill do you mean drill a pilot hole that is the same diameter as the dowel?
What is "PL adhesive? PL?

Start a hole with a forester bit, the same size as your dowel 1/8 deep.

Cut your dowel 3/16 or 1/4 inch longer than your inside dimension.

Bend and insert. Probably the ply will fail before the PL.

[lbwdog]

I'm just wondering how easy it is to bend a 1" dowel!

[Greenman]

Originally Posted by lbwdog

I'm just wondering how easy it is to bend a 1" dowel!

Start one end in one of the holes and pound it into the other. It'll go.