Slim THTLP

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Seth
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Re: Slim THTLP

#46 Post by Seth »

JensToft91 wrote: Mon Jan 24, 2022 2:31 pm ...I don't have the driver, so I just have to hope that the dimension are accurate...
Think long and hard about this. Is that a gamble you're willing to take? I can't say I wouldn't, but just be prepared to get really creative in the case that it's not close enough. If the hole is too small, you're gonna have to get in there with something to open it up. If it's too big, you're gonna have to figure out a way to fill some space, or convert it to a removable baffle setup.

To be really honest, I've had the driver right in front of me and still cut it wrong. So, maybe it doesn't really matter after all. Well... for me anyway. :lol:

As far as putting the side on a slightly wonky assembly, I've had that a time or two. You certainly have a better vantage point, but I don't think I'd do it in sections. I've found that if I use screws and work my way down the most crooked side straightening and screwing as I go, using the length of the side as leverage, I can get it straightened out pretty darn well. Then I work the next edge, usually the short side. The final side can take some good tugging, clamping, strapping, banging , and swearing to get it as straight as possible. What that doesn't fix can usually be hidden with bondo and having the cab flush trimmed and rounded over. I think you said you're laying your cab down. If the cab's got a twist to it, consider putting 3 feet on the bottom. The tripod arrangement will eliminate any wobble in the cab.

This site doesn't get a ton of traffic. But be assured, there are plenty of people eager to read of your progress and see the photos. This thread's been up for 12 days and there are almost 600 views. That's about 50 people checking out your progress per day. I'm completely loving every post. Keep it coming Jens!

Did you see in ecut1's THTLP build thread where he mentioned "It goes noticeably lower than the TT's and there's much more "feeling" in the bass now."? I figured that would be music to your ears after deliberating about whether or not a THT would be worth it and actually deliver the bottom end you desire. I look forward to your report soon too!
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Seth
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Re: Slim THTLP

#47 Post by Seth »

JensToft91 wrote: Mon Jan 24, 2022 8:03 am Just realised a big mistake. I alligned panel 7, so the distance is the same to panel 1 at the top as it is on the buttom. But with the first side curved, that won't be a 90 Deg angle. Panel 8 is attached to panel 7, which will give it the same "not"-90 Deg angle. Panel 10 can't be rectangular now, as it won't allign with panel 8.
This will also make it impossible to straighten the curve 🙄
Well. The horn probably won't realise that it's not rectangular 🤔
I'll fit panel 6 and 9, and then cut panel 10 to fit.
I'll then split the other side's into multiples, without 45 Deg angles, as the side will end up as curved as the first. I won't be able to fit the 45 angle sides together.
The will probably not be the prettiest THT. But I won't quit until it works 👍
Had to put this up to follow along.
Screenshot (166).png
Still not sure I quite understand though.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

JensToft91
Posts: 140
Joined: Sun Feb 28, 2021 6:43 am

Re: Slim THTLP

#48 Post by JensToft91 »

Wow! Thank you all 👍
I'll keep posting updates.

I'll take my chances with the baffle, and get creative if it fails. My attempt on the TT was spot on. (No offense Seth 😅)

And uh! Just writing this, I realised I have a 12 inch sub lying around, with the exact same cut-out dimension. I'll use that as a test-fit 👍

I'll make a drawing to explain the panel misalignment, sometime this week.

JensToft91
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Re: Slim THTLP

#49 Post by JensToft91 »

Seth wrote: Tue Jan 25, 2022 3:31 am
JensToft91 wrote: Mon Jan 24, 2022 8:03 am Just realised a big mistake. I alligned panel 7, so the distance is the same to panel 1 at the top as it is on the buttom. But with the first side curved, that won't be a 90 Deg angle. Panel 8 is attached to panel 7, which will give it the same "not"-90 Deg angle. Panel 10 can't be rectangular now, as it won't allign with panel 8.
This will also make it impossible to straighten the curve 🙄
Well. The horn probably won't realise that it's not rectangular 🤔
I'll fit panel 6 and 9, and then cut panel 10 to fit.
I'll then split the other side's into multiples, without 45 Deg angles, as the side will end up as curved as the first. I won't be able to fit the 45 angle sides together.
The will probably not be the prettiest THT. But I won't quit until it works 👍
Had to put this up to follow along.
Screenshot (166).png
Still not sure I quite understand though.
Illustations not to scale. Only to show the principle of what I'm trying to describe.

Panel 7 has the same distance to panel 1 in the top and buttom. But i forgot that this can't be true, when the panel is curved. So now panel 7 is attached at an angle. Panel 8 is attached to panel 7 - must be the same angle. Panel 10 won't be able to fit now, if it's rectangular.

Panel 8 on the illustration should be 10*
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ACUA
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Re: Slim THTLP

#50 Post by ACUA »

You are dealing with plywood similar to what I am used to. It took me several cabinets to realize the effects of bowed panels across a build. I am still not in a position to boast that I have mastered it by any means. I initially figured that I could just bend the panels into proper shape as I went along with muscle and brad nails. As I did so I could get most the joints to align but as my builds progressed my fatigue and margin of error always grew and by the end even if the end piece fit the whole of the cabinet was still a twisted mess. It is tricky for me to stack my quad tuba 45s together as the out of squareness compound depending on the orientation. Today I would claim that I have sorted out some of those issues. For me, for what ever reason, it has been hard to follow the build plans where the L jigs and wax paper are specified. Dados have become my friend as of late, just have to compensate for the dimension changes along the way.

I thought I had some advice to post but it turned into a been there done that rant. I guess what I would say is for me, learning how to conceptualize in a 3 dimensional level the effects of a bow or how two small bows interact has helped me to visualize the build along the way and I am getting better at planning ahead. I better understand when extra effort is needed to straighten a panel or if it will straighten with the install of a later panel. I also have excepted that even though I get each joint to line up that does not ensure that the cabinet is squaring itself up over time, the result of my measurements and cuts being off slightly actually caused some out of square-ness and can compound the problems. If I slow down and check for square across the entire build before and after each panel install it helps me keep on track.

My last build I took extra care to clamp my starting panel the side or piece which all panels attach too, to my table. I made sure my table was pretty flat and I clamped the piece so that it became flat. This really improved my build. It is funny but an 1/8in bow to that base/side panel can really screw up the build if it is not dealt with.

Live and learn, no judgment here, I am a fool who is trying just like you. I appreciate you sharing your build. It is fun to see you overcome the challenges. Good work.
Advanced Concepts Underground Audio

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Bryan Cox
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Re: Slim THTLP

#51 Post by Bryan Cox »

JensToft91 wrote: Mon Jan 24, 2022 2:31 pm Baffle drawing. I don't have the driver, so I just have to hope that the dimension are accurate. They were on the Dayton for the TT, so I guess this will work aswell.
I didn't have the driver when I built my first T39. I used the spec sheet from Eminence. However, I don't think I'd do that again as I had to sand a little more material off to allow for expansion of the driver frame. If I'd made it too large then my whole box would've been trash. My $0.02, wait for the driver.

As for the warped panel....I think I'd start over. But short of that, you could spray water on the concave side of the warped panel, let it soak in, then affix the edge of straight 2"x4"s perpendicular to the longitudinal axis (using meaty wood screws). If you take your time this should straighten the warp out enough to continue. Just remember to place the screws in a location so that you can remove them later. After all your panels are in place (ideally before you close the box up) remove the 2"x4"s. If your box still wants to warp, then clamp the 2"x4"s inside the mouth to straighten the warp out while the PL from the final panel cures. This process is a PITA but it can work if you take your time.

This is how I did it and it worked out relatively well.
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Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

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Bill Fitzmaurice
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Re: Slim THTLP

#52 Post by Bill Fitzmaurice »

Most of the warp in that panel should have been pulled/pushed out with the installation of panels 2 and 6. If still warped at the other end a temporary brace the same size as panel 6 could have been screwed to the side and panel 1.

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Seth
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Re: Slim THTLP

#53 Post by Seth »

JensToft91 wrote: Tue Jan 25, 2022 6:37 am Illustations not to scale. Only to show the principle of what I'm trying to describe...
Great modeling skills Jens :thumbsup:

Make panel 10 rectangle and MAKE it fit. That's what forces the warp out of the other panel... securing it to parts that are true.

The route I'd first try is secure 10 to the side first, with as many screws as it takes to pull that little section of side snug and true to the short dimension of panel 10. Guessing only 2 or 3 would be needed for that short distance. Then, using the length of 8 as leverage, use a clamp to pull the 8/10 gap closed and secure 10 to 8 with brads or screws.

If the warp is being really stubborn, put a couple strips of lumber on the outside of the cab like Bryan said, straddle panel 10's location so you still have access to fasten 10 and screw them to the outside of the side panel from center if the inside of the panel to force the warp out and then put 10 in like mentioned above.

Do as much as you can reasonably do to pull that warp out and avoid letting the warp dictate panel dimensions. Fight back! Show that piece of lumber who the boss is, Jens! :evil: :cussing: :chainsaw:

It's the unfortunate tradeoff of using budget lumber. All but one of my builds have been out of budget lumber. I'd use it again. Just takes more effort to build as square and true as possible.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

JensToft91
Posts: 140
Joined: Sun Feb 28, 2021 6:43 am

Re: Slim THTLP

#54 Post by JensToft91 »

So many suggestion! Thank you all.

Fortunately, I got the other side sawn an inch or two wider than the first one, as the TT was a hard fit (curved as well).

So the box will end up as straight as possible - but I don't want to fight it too much. I'll focus on making this as tight as possible, so I know it functions as intended. The other side is warped as well - and by being longer it should fit right on top. What's lost on the "inner curved" is gained by the "outer curve". At least I hope so.
I will probably end up splitting the side, as I don't feel confident enough in how well it seals up. With a split side, I can chaulk the joints as I go along. The I'll punish it by sanding the shit out of it, and hide my mistakes with paint.
Function over looks.

JensToft91
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Re: Slim THTLP

#55 Post by JensToft91 »

Regarding the baffle cutout.

Here's the thing. I know I'm not strong enough to fight the urge to testrun the sub when I get the driver. Aaaand my will power is even weaker, when it's time to disconnect my new subwoofer and finish it.

So if I wait for the driver, I know for a fact that a raw sub will sit behind the couch and stare at me for several years.

The driver being late is probably my only chance of actually finishing this sub, and get it nice and pretty for the living room 🙄

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AntonZ
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Re: Slim THTLP

#56 Post by AntonZ »

A man has to know his limitations and apparently you do :cowboy:

Don't sweat it, I would think worst case the driver chamber is big enough for an adapter plate.

JensToft91
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Re: Slim THTLP

#57 Post by JensToft91 »

Well, I have learned after too many unfinished projects 🤔

Yea!. Worst case will be this. Maybe I'll wait with the inside stiffeners so there's space for emergencies.

ecut1
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Re: Slim THTLP

#58 Post by ecut1 »

If you haven't built panel 6 you might consider mounting the driver with a plate like the high excursion driver instructions (like AntonZ mentioned above). My panel 6 cut out ended up a little large because my router circle jig is homemade. I didn't realize the nail I was using for the center point was allowing the whole jig to rock about 1/16 of an inch which left me at about 3/8 over instead of 1/4. I was worried about it at first because the hole ended up pretty close to 17" leaving only a half inch on the top and bottom. In the end it sealed up great... I just didn't fasten anything in that thin area (just tons of glue). Moral of the story... you could probably cut the panel 6 hole with a little wiggle room and then build your mounting plate once the driver arrives. If you do it that way, the chamber braces will have to be custom fit.

JensToft91
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Re: Slim THTLP

#59 Post by JensToft91 »

I've tried the router-nail issue as well, it's so annoying, to have measured everything exactly right, and then the hole ends up way off.

Quick update:
If I believed in signs from above, the cracked saw 1 inch from the finish line mig scare me abit.
Then the dog ran off with one of the screw retention blocks.
Hmm. Taking my chances anyway.
My boy had great fun with throwing the retention blocks through the hole.
Testfit with a another 12 inch.
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ACUA
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Re: Slim THTLP

#60 Post by ACUA »

That’s awesome, cracked me up!
Advanced Concepts Underground Audio

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