THT LP build

[slinger]

Hello. This is my first BFM build and I am building a THT LP with 23.5 panels for an overall 24.5 finished product. I am using the bash 300 and the recommended Dayton DVC 385-88 woofer. I am hoping this will be an upgrade to my current dual MFW-15 setup. I will post as many pictures as I can and would love any feedback. I have a question. Can I do more than one panel in a day or do I have to wait until one panel dries until going onto the next?

Thanks, Drew

[Radian]

Can I do more than one panel in a day or do I have to wait until one panel dries until going onto the next?

There's many ways to go about this.

My technique is to dry-fit the entire cab first, making sure all the pieces fit precisely together without adhesive, then take it all apart and finally glue-up in one or two marathon assembly stages.

[Bill Fitzmaurice]

Can I do more than one panel in a day or do I have to wait until one panel dries until going onto the next?

There's many ways to go about this.

My technique is to dry-fit the entire cab first, making sure all the pieces fit precisely together without adhesive, then take it all apart and finally glue-up in one or two marathon assembly stages.

That's OK if all your wood is perfectly flat. I do two, maybe three panels a day. That's enough to fill a couple of hours work, and allows you to use warp removal techniques.

[Ryan A]

You may do more than one panel per day, provided the panels are mechanically secured until the adhesive dries.

Many people start to cut corners when they get tired or work too long, which is a good reason to take it slow and do just a few panels at a time.

[67baja]

I agree that you can do more panels if you use screws to hold them while the adhesive sets. I built most of my cabs as marathon sessions working from 9 in the morning until 10 ish at night. You can build your tht in a weekend this way.

Good luck!

[Drey Chennells]

Hello. This is my first BFM build and I am building a THT LP with 23.5 panels for an overall 24.5 finished product. I am using the bash 300 and the recommended Dayton DVC 385-88 woofer. I am hoping this will be an upgrade to my current dual MFW-15 setup. I will post as many pictures as I can and would love any feedback. I have a question. Can I do more than one panel in a day or do I have to wait until one panel dries until going onto the next?

Thanks, Drew

Don't mount the amp in your sub. Make yourself some stout 90deg jigs to clamp against to set up your brad nailing. Yes it will be an upgrade.

[slinger]

Thanks for all the replies. I expected to see more of the PL premium coming out of the sides of the joints than I do. How big should the bead of PL be? Will it expand ovenight? I attached the side to panel 1 around 7pm.

Thanks, Drew

[miked]

How are you securing the panels to each other? Screws or brad nailer? I realize that with PL, the panels slide around a lot when you're trying to get them aligned and nailed down. That's all part of the fun, my friend! Ideally, you want to PL the joint, line the two panels up together, then drive one screw or one brad just to hold it in place. Then you clamp the crap out it and continue to screw/nail it in place. Then you don't touch it until the next morning. These cabs are not jigsaw puzzles that can be assembled in one sitting. That fact is frustrating to me as well.

The size of the PL bead depends upon how much space it will have to fill. I.E. if your cuts are all precisely the correct size, and when you dry fit the panels you can't see any light peeking through that joint ANYWHERE, then you only about a 1/4" wide bead on 1/2" material. If you have gaps to fill, slather the PL on there and let it sit overnight. PL EXPANDS big time as it dries, which is exactly why it is so important to let the assembly sit overnight. If the whole thing is clamped AND the temperature in your assembly room is over 80F (PL is VERY temp sensitive AFA curing goes), you can probably get away with removing clamps after 8 hours or so.

When PL is fully cured, it's like concrete. It's impossible even scrape the crap off, let alone break a bond b/t panels. But you've got to let it cure.

If you don't see a lot of sqeeze out, that POTENTIALLY means that joint is not air-tight. If possible, hold a flashlight on one side of the joint and eyeball the other side as you slide the flashlight around. If you see light, you need to slather PL in that area. NO squeeze out is bad for sure. A little squeeze out PROBABLY is not bad. Lots of squeeze out is great, but also means you used too much PL on that joint. PL usage and cab building is a learning process. I can dry fit two panels and know exactly how much PL I need to use. That said, I still make a lot more mistakes than I should at this point. Check my build thread, link in sig for some potentially helpful hints.

*edit*
Saw your pic. IMO you need to be laying down a wider bead of PL and really clamping those panels together. Bill's designs are pretty forgiving of "airspace errors" but they absolutely require airtight joints. Particularly with one of the subs, that puppy needs to be airtight. PL is cheap; blown drivers aren't.

[slinger]

Ok thanks miked. I'm hoping there will be more squeeze out by morning. If not I will PL the seam and use more on my next panels. I am going to screw together panels dry the remove add PL then re screw.

[miked]

Ok thanks miked. I'm hoping there will be more squeeze out by morning. If not I will PL the seam and use more on my next panels. I am going to screw together panels dry the remove add PL then re screw.

PLing the seam, AKA "a finger fillet" works very well. PL seals airtight, just like silicone does, but once it dries, it grabs like concrete, which silicone does not. In my Omni Top build, I "finger filleted" many of the joints, even though I probably didn't have to. It's a holdover habit from 20 years ago when I would build subwoofer boxes for the trunks of cars and use white bathtub caulk to seal the joints. Old habits die hard. But again, PL is cheap.

PL expands as it dries. Whatever squeeze out you have after 3-4 hours will not significantly expand in the following 3-4 hours. "PL fillet" that joint, let it dry, and move on.

[slinger]

Here is a pic of the Baltic birch I'm using.

[miked]

That's good BB. Best stuff to use. Your method "screw together, unscrew, PL, rescrew" is great. It's a proven, successful construction method.

[Bill Fitzmaurice]

Thanks for all the replies. I expected to see more of the PL premium coming out of the sides of the joints than I do. How big should the bead of PL be? Will it expand ovenight? I attached the side to panel 1 around 7pm.

Thanks, Drew

Judging by your location I'll go out on a limb and assume it's not all that humid. PL needs a fairly humid, and definitely warm, environment for full expansion. After you fasten the joint use a spray bottle to spritz some water mist on the joint, and be sure the room temperature is at least 65F.

[slinger]

I am assembling the THT LP in the basement as I figured it was too cold in the garage. I think I will make the bead bigger on next panel and cock the seam of the first panel to make sure it is sealed.

[slinger]

Here are some more pictures of my progress. For panel 4 can I just dry fit it to the other side panel until PL dries? Or how do I get the proper height of the panel on the clamping side? Is my panel 2 being slightly higher than panel 4 (first pic) going to be a problem?

Drew