BillFitzmaurice.info

I'm starting construction on a narrow THT and I thought I would make a thread showing my progress. While it may open me up to some scorn I'm deviating from the plans a little bit. I'll be using a Rockford Fosgate P2D2-12 driver (it has very similar specs to the Dayton RSS315HF and costs $60 less), I moved the access panel to the front of the cabinet, and I'm using regular Titebond II wood glue.

This cabinet will be 15" wide internally and will be built out of 1/2" baltic birch plywood. I'll most likely be staining the cabinet when its done so I want to keep the wood looking as nice as I can. Here are some pictures of my progress thus far:


I cut the side panels 1/4" oversize so I can come back and trim them perfectly flush after the cabinet is complete. My panel 1 is split in two to allow for the access door.


Panel 2 is being glued in. It required some creative clamping techniques to get good pressure on the middle of the panel.

Triticum Agricolam wrote:...and I'm using regular Titebond II wood glue.

How do you plan on making all the wood connection joints air-tight? Titebond II does not fill gaps, nor does it expand, and both qualities are required for the build. Any air leak will severely compromise output.

DJPhatman wrote:

Triticum Agricolam wrote:...and I'm using regular Titebond II wood glue.

How do you plan on making all the wood connection joints air-tight? Titebond II does not fill gaps, nor does it expand, and both qualities are required for the build. Any air leak will severely compromise output.

Lol, I knew someone was going to bring that up. PL Premium is a good adhesive and I keep a tube in my woodshop for situations that require it, but it always ends up making a mess, so I don't use it if I don't need to. The gap filling properties of PL Premium are very handy, but they are something that I very rarely need to take advantage of. I build a lot a of cabinets, getting the accurate cuts needed for an air tight joint isn't any trouble for me.

Triticum Agricolam wrote:

DJPhatman wrote:

Triticum Agricolam wrote:...and I'm using regular Titebond II wood glue.

How do you plan on making all the wood connection joints air-tight? Titebond II does not fill gaps, nor does it expand, and both qualities are required for the build. Any air leak will severely compromise output.

Lol, I knew someone was going to bring that up. PL Premium is a good adhesive and I keep a tube in my woodshop for situations that require it, but it always ends up making a mess, so I don't use it if I don't need to. The gap filling properties of PL Premium are very handy, but they are something that I very rarely need to take advantage of. I build a lot a of cabinets, getting the accurate cuts needed for an air tight joint isn't any trouble for me.

This is the time that you need to use it. And, as an experienced woodworker, you also know the there is no such thing as a "perfect" joint. If it could be done, it would be a recommended practice. It isn't because you cannot cut a "perfect" air-tight joint with wood.

FTR, PL Premium is not the only expanding polyurethane adhesive, it is simply the cheapest option in the USA. But, choosing to not use the correct type of expanding, gap-filling adhesive to seal all of the joints is nearly guaranteeing your build to fail being air-tight, let alone having a decent amount of structural strength. We can only recommend to you what to use and why. Your failure to follow the advice on this forum, and/or the plans directions, will, in all likelyhood, cause your build to fail due to air leaks. Even the tiniest of pinhole leak can completely ruin output.

Just know that I, personally, don't usually say things on here to be an asshole. I recommend what works, and why. I try very hard to discourage any builder from straying far from the plans, but especially from using the wrong adhesive. Once you put the 2nd side on, you can't go back to fix any air leaks along the horn path. Don't like the mess PL makes? Try Gorilla Glue polyurethane expanding adhesive. Or, any other brand of expanding, gap filling adhesive.

DJPhatman wrote: Don't like the mess PL makes?

I personally don't know what all the fuss is with "the mess PL makes"... what mess? IME eating golden syrup and cream crepes with your hands can be messy if you're not careful, but using PL is a simple affair; remove plug from caulking gun, use caulking gun to make small PL bead, release pressure on gun just before end of said bead and replace the plug, voilà! No mess!

The crepes on the other hand, thats a different story...

commander_dan wrote: I personally don't know what all the fuss is with "the mess PL makes"... what mess?

+1. If it makes a mess you're using too much.

DJPhatman wrote: This is the time that you need to use it. And, as an experienced woodworker, you also know the there is no such thing as a "perfect" joint. If it could be done, it would be a recommended practice. It isn't because you cannot cut a "perfect" air-tight joint with wood.

FTR, PL Premium is not the only expanding polyurethane adhesive, it is simply the cheapest option in the USA. But, choosing to not use the correct type of expanding, gap-filling adhesive to seal all of the joints is nearly guaranteeing your build to fail being air-tight, let alone having a decent amount of structural strength. We can only recommend to you what to use and why. Your failure to follow the advice on this forum, and/or the plans directions, will, in all likelyhood, cause your build to fail due to air leaks. Even the tiniest of pinhole leak can completely ruin output.

Just know that I, personally, don't usually say things on here to be an asshole. I recommend what works, and why. I try very hard to discourage any builder from straying far from the plans, but especially from using the wrong adhesive. Once you put the 2nd side on, you can't go back to fix any air leaks along the horn path. Don't like the mess PL makes? Try Gorilla Glue polyurethane expanding adhesive. Or, any other brand of expanding, gap filling adhesive.

Thanks for your input DJPhatman, I know that you have honest intentions and are only telling me these things because you really would like me to have a successful build. I fully acknowledge and genuinely appreciate that. With that being said, there really isn't anything anybody can say to me that is going to convince me that a expanding polyurethane type glue is an absolute requirement for building an air-tight THT. I can certainly see why it would be the best choice for many, if not most, people looking to build these cabinets though.

Like I said before, I build a lot of cabinets, I built over thirty last year alone. I have reached the point that it is something I can do very well. I am confident in my ability to build an air-tight cabinet using Titebond glue. If you would like to see some examples of what I have built I have tons of pictures on my facebook page here: http://www.facebook.com/triticumaudio

I recognize that I might be wrong and am making a mistake, but that's a risk I'm willing to take. If it turns out I can't build an air-tight cabinet I will be more than happy admit to it here so that, if nothing else, I can serve as an example to others of what not to do and why you should strictly follow the instructions

Let me say again, I appreciate yours and anyone elses input, even if I don't always follow the advise. I'll be posting lots of pictures as I go. Maybe when you see my work for your self it will increase your faith in me a bit

Triticum Agricolam wrote:With that being said, there really isn't anything anybody can say to me that is going to convince me that a expanding polyurethane type glue is an absolute requirement for building an air-tight THT. I can certainly see why it would be the best choice for many, if not most, people looking to build these cabinets though.

Have you considered the pressures involved and the inflexibility of Titebond? One of the properies of PL is that it does have some flex. While it may be true Titebond holds just as well if not better on a well prepared surface... but over time wood flexes and expands and contracts and Titebond won't expand and contract with it. Even if you have a perfectly sealed cabinet on day one, it may not remain so throughout its life. PL or other PU adhesives will stand up better over time.

Use whatever adhesive you like, of course.

I have built a ton of cabinets, and the only joints that really need to be air tight and perfect for cabinets are the face frame butt joints, which really isn't that many joints or that many linear inches of perfectly tight butt joints per cabinet. The rest of the cabinet joints are in some sort of rabbet or dado and not flush butt joints. A THT has about 50 panel butt joints and they all have to be perfectly tight along the entire perimeter which amounts to hundreds of linear inches of plywood butt joints per cabinet. It certainly could be built with great carpentry skills, perfect cuts, and tightbond glue, but it isn't worth the risk or time for most builders.

BrentEvans wrote:
Have you considered the pressures involved and the inflexibility of Titebond? One of the properies of PL is that it does have some flex. While it may be true Titebond holds just as well if not better on a well prepared surface... but over time wood flexes and expands and contracts and Titebond won't expand and contract with it. Even if you have a perfectly sealed cabinet on day one, it may not remain so throughout its life. PL or other PU adhesives will stand up better over time.

Use whatever adhesive you like, of course.

Titebond is certainly not inflexible. You can flex and peel Titebond right off of any non-porous surface without it breaking. You should see how guys use it to clean vinyl records.

A whole lot of people build a whole lot of speaker cabinets using Titebond. If the movement of the wood was enough to weaken the bond, there would be a ton of leaky cabinets out there.

caddylackn wrote:I have built a ton of cabinets, and the only joints that really need to be air tight and perfect for cabinets are the face frame butt joints, which really isn't that many joints or that many linear inches of perfectly tight butt joints per cabinet. The rest of the cabinet joints are in some sort of rabbet or dado and not flush butt joints. A THT has about 50 panel butt joints and they all have to be perfectly tight along the entire perimeter which amounts to hundreds of linear inches of plywood butt joints per cabinet. It certainly could be built with great carpentry skills, perfect cuts, and tightbond glue, but it isn't worth the risk or time for most builders.

I agree, for most builders Titebond probably isn't worth the risk, but I like a challenge.

At this point I pretty much feel obligated to use Titebond, just to see if I can prove you non-believers wrong

Thanks everyone for your input.

Made some more progress on the THT. The one big drawback to the driver I'm using is it can't be reverse mounted, so Rockford Fosgate gets -10 points. I just made an adapter plate which the sub front mounts to. Would have been easier if I had just gotten a driver that can be reverse mounted, but apparently I like doings the hard way.

Here is the sub with the mounting plate, the groove around the outside of the plate is for some gasket tape to ensure I get a good seal:


Gluing in the screw mounting blocks to the back side of the baffle:

Triticum Agricolam wrote:I recognize that I might be wrong and am making a mistake, but that's a risk I'm willing to take. If it turns out I can't build an air-tight cabinet I will be more than happy admit to it here so that, if nothing else, I can serve as an example to others of what not to do and why you should strictly follow the instructions

Let me say again, I appreciate yours and anyone elses input, even if I don't always follow the advise. I'll be posting lots of pictures as I go. Maybe when you see my work for your self it will increase your faith in me a bit

Good luck with the build and keep posting the beautiful pictures

The final words in construction are:
1. Passes a high power leak check
2. Passes an impedance sweep (which you'll need to confer with Bill because of the Rockford Fosgate driver)

P.S. - A vented cab is not air tight by design. Tuned yes, but not air tight like these horns need to be....by any stretch. They are an instrument, not simply a cabinet.

Got some more time to work on the THT tonight. Here I am gluing in the driver mounting panel:


Here is a close up of the glue line, for you Titebond naysayers


Fifth panel being attached:


I'm getting a lot of use out of my tapered cauls on this build:

You certainly seem to be able to build a box judging by your other work. Hopefully this one is as well made and air tight as it needs to be, dude. Keep it up.

I too have built a jillion cabinets. Occasionally I use yellow glue for some styles, but none of Bill's. It can be done, no doubt. If I were doing it with a horn though, I'd caulk the joints. It's not so much about the strength (pl is stronger, I tested it) as it is the air. Even a pinhole will affect performance. Pl is as much about insurance against that as anything else.


You should run an impedance sweep when you're done if you're able.

Nice work btw.