BillFitzmaurice.info

Gregory East wrote:Real deal PL bond will break out the ply on a rightangle butt joint.

Been there, done that. PL is crazy strong when applied properly

I hope you heed the advice of those who come before you and made the mistakes so you don't have to.

What the others have said is the truth, (un)fortunately. The 12mm( 1/2") 5 or 7 ply is plenty sufficient. Unlike conventional boxes, Bill's cabs are braced properly, and in the subs, the panels themselves are the braces for the side panels.

Using that plywood as shown will undoubtedly not let the cab be air-tight, which in turn will not let the driver do it's work properly......likely causing one to push the driver harder until the magic smoke appears.

Building these cabs is different from conventional cabs, so read, read, and reread the plans until you can build it with your eyes closed. This is not said with anger or disdain, but only to help.

Thanks Tom.

I feel the love...

If PL bonds to that finish I don't see a problem. The guys seem convinced it won't bond but there's moisture in the unsealed edge.

I tested PL equivalent on pvc, no dice. It stuck "on" but broke away clean.

On another note, quirks of bass in smaller rooms being what they are, be prepared for the location to possibly not work for your listening position.

Thanks...starting to wonder if it's all worth it....wrong glue, wrong ply, possibly wrong placement, what next...., wrong driver, amp..?

Oh boy, wrong glue? Seriously? You need expanding polyurethane for the expanding gapfilling. Pressures in the driver chamber and throat are extreme. PL is available in Aussie now.

Before you go hoisting your cab up there, put the sub where you sit and see if there is good bass up where you intend the sub to be.

Gregory East wrote:Oh boy, wrong glue? Seriously? You need expanding polyurethane for the expanding gapfilling. Pressures in the driver chamber and throat are extreme. PL is available in Aussie now.

Before you go hoisting your cab up there, put the sub where you sit and see if there is good bass up where you intend the sub to be.

Hi Greg

No, I have used poly glue...it's just that the substrate on the ply is a smooth finish...so the forum members have said it's not going to work. I'm just testing some pieces now...if not, I will change plans. An easy fix is to relay the existing two black elevations with a thin ply. Note - all my internals have been cut already...so I don't want to throw away a couple of hundred bucks of wood. By relaminating the two built pieces, I will be OK....as all the other ready-cut panels do not have the black surfece on the ends, where they glue.

Then, I'll be on speaking terms again with the forum buddies...!;-)

Oh, for testing leaks....Bob's suggestion is good re the use of the flexi pipe...but this will only test the outer cabinet walls...not certain sections of the internals...eg near the horn throat. How do you know if ALL of the internal pieces are free from leaks?

Atilsley wrote:Oh, for testing leaks....Bob's suggestion is good re the use of the flexi pipe...but this will only test the outer cabinet walls...not certain sections of the internals...eg near the horn throat. How do you know if ALL of the internal pieces are free from leaks?

Blowed if I know, but using the real deal PL is a good start.

You'd have to do a stellar laminate job, better to get some more ply for top and bottom. And rout off a couple of plys where your sides join.

OK, thanks guys for your insights.

Before I progress anyfurther, I'm doing some testing on the poly adhesive with this substrate on the ply.

The poly product is expensive, and the instructions state it is the expanding type, moisture triggered, and can be applied to porous and non porous surfaces. The dry time is 12-16 hours.

http://www.selleys.com.au/adhesives/con ... s-platinum

I've taken two samples and created a 90 degree join to test the strength of the adhesive. See pics.

I will assess tonight by prying the joints apart.

If they simply pop apart cleanly, I will know my build has failed. If the adhesive holds securely, I will continue on my project.

Perhaps we need a new rule #3. 'If someone has done something wrong, but has thoroughly tested the fix, then they should be encouraged by fellow forum members to proced with the fix in order to save throwing in the towel and starting over....and in all cases, pleasantness and civility applies.'

Atilsley wrote:Oh, for testing leaks....Bob's suggestion is good re the use of the flexi pipe...but this will only test the outer cabinet walls...not certain sections of the internals...eg near the horn throat. How do you know if ALL of the internal pieces are free from leaks?

Use a light on one side of the panel and if you can see it on the other you have a leak, or compressed air and sawdust. Then once you are certain you have no leaks make sure your panels are level on the last side, test and retest dropping the last side in place, THEN goop a ton of PL on all the edges. That is about it.

Your ply may work to a minor degree but do you really want to go through all the trouble of the build, mounting, finishing everything to have a joint come loose from the vibration of the cab itself. I get that you don't want to waste the wood but unless you dado every joint and brace location you are taking a big risk. Also your path will still be off from the oversized ply. Think of it as trying to ice skate with roller blades, it can be done but getting ice skates is really the way to go.

Lastly WE are encouraging you, to follow the plan!

Your crossways joint isnt really a representative test, I guess it will show if your glue sticks to the phenolic coat, but you really should have a compressed squeezed out layer of it.

Scary little amount of squeezeout showing there doesn't bode well. If it was PL it would be all over the place, maybe too quick with the camera?

Gregory East wrote:Your crossways joint isnt really a representative test, I guess it will show if your glue sticks to the phenolic coat, but you really should have a compressed squeezed out layer of it.

Scary little amount of squeezeout showing there doesn't bode well. If it was PL it would be all over the place, maybe too quick with the camera?

Thanks Greg. Certainly, the adhesive continues to pour out of the tube when you stop squeezing. Perhaps this PL product doesn't have the same aggressive expansion you are used to.

Also, I'll be adding additional sealing to all the internal joins after the gluing up of panels.

Further, the screw/glue build process is per Bill's plan. I'm using three inch course thread wood screws...placed each five inches.

Squeezing out of tube not same thing. We're looking for moisture induced curing expansion.PL is not generic for polyurethane, it's a product line of Loctite. PL Premium is the goto one, cheap enough even in Aussie.