4T speaker build, Rebooted

[BigguyZ]

OK, so I want curved speakers. To accomplish that, I was doing a stacked lam with MDF. I didn't have the $$ to use blatic birch, and I've read too many threads with Ply laminations delaminating, and MDF is at least pretty stable.

Here's the thread here:

https://www.htguide.com/forum/showthread.php?t=36251&highlight=4ts

I got pretty far in the project- I have laid out all of the pieces (about 60 of them), and drilled the alignment holes that are used to make the part from the template, and eventually for alignment during assembly. Here's all of the MDF sheets (cut into quarters or so). I'll have to find a use for it all, as that's a lot of material.

However, earlier this year I had a bit of an accident while trimming one of the layers on my router table... Don't look if you're squeemish.

https://www.htguide.com/forum/showthread.php?t=36112&highlight=lacerated

So, after that- and with the amount of work/ time it would take to cut and trim all of the peices in general- I decided to scrap the stacked lam idea and use a rib and sheath construction, as several people have done.

[Solid7]

OK, so I want curved speakers. To accomplish that, I was doing a stacked lam with MDF. I didn't have the $$ to use blatic birch, and I've read too many threads with Ply laminations delaminating, and MDF is at least pretty stable.

Delamination with Baltic Birch? MDF Stable? I don't mean to be a naysayer, but MDF has it's own problems, especially if you have to drive dowels into it, or if you stack too high. MDF doesn't delaminate in layers, but it will pull apart like a dry peanut butter sandwich in the material between glue layers. Your glue joint most likely won't fail, but the material itself, will. I have had this happen many times. I know that cost is a factor, but I would trust the BB ply over the MDF any day of the week.

One suggestion - make your sections extra thick, and make permanent tension clamps in the walls, using all thread, nuts, and washers. 1/4" works nicely. I usually try to make my wall thickness at least 1 1/4". Do not overtighten!

[BigguyZ]

I couldn't afford BB- I'm referrring to other birch plys as far as delaminating.

And unless you soak it in water, I've found MDF to be pretty stable. At least in the application that this would be in. I'm not talking about using it as a bookshelf, after all.

But anyways, that's no longer pertinent to the current build.

[BigguyZ]

Even though I had a template for the speaker already built, I needed to make a new one where the edge of the template defines the interior of the speaker.

The first picture is of the new template design. I want symmentry, so my thinking is it's easier to do the layout for one half of the template, and transfer that twice to make a full template.

To create the layout, I simply took the cross sectional area of the original design to determine what the total area needs to be. I know that the front baffle needs to be the same width, but everything else can change. Using graph paper, I counted full square inches, and then approximated the area for the last 5 or square inches worth.

Then, I transferred the outline to the MDF, referencing the square corner of the MDF sheet. I rough cut the outline of the half template with my jig saw, and then shaped to final dimensions on my disc sander.

Then, I transferred the outline of the template half to a larger piece of MDF, using the edge of the MDF and middle line as a reference point. Then again, I rough cut with the jig saw and shaped to the line on the disc sander.

And that's how I created the template for the braces/ ribs.

[Jed]

Glad you are at the 4T build again. I must have missed your original post when you had your injury. It's one of my worst fears that people will have injuries building one of my speakers. I hope you have a full recovery and things are back to 100%.

[BigguyZ]

Glad you are at the 4T build again. I must have missed your original post when you had your injury. It's one of my worst fears that people will have injuries building one of my speakers. I hope you have a full recovery and things are back to 100%.

It's healed as much as it will be, for now. But I have very little feeling in the area that was damaged. I plan to have surgery to attempt to get the nerve to grow back, but that'll still only get me to where the finger can sense hot/cold, and some pressure. Even so, I'm happy that it wasn't worse! I could have easily lost the finger...

I have a lot more progress pics, but I'm having difficulty getting them off of my phone. I'll add an update this evening.

Edit: Jed, I just thought of a question for you, and I might as well ask it in the thread. Why was the 1s discontinued, and what would you reccomend for a substitute?

[Jed]

Edit: Jed, I just thought of a question for you, and I might as well ask it in the thread. Why was the 1s discontinued, and what would you reccomend for a substitute?

I'll still sell it if you want to match the original Dynamic Series, which uses the XT25 tweeter. I "discontinued" it because I don't have a version with the HDS tweeter developed to match the rest of the MK2s.

[BigguyZ]

Jed-
Would the old 1s design match well with the MK2s? I'm open to other designs for the surrounds, as long as they'll match.

Here's the next batch of progress pics. The first one is one of the ribs rough cut from the sheet of ply. with this project, I did want to use plywood for it's structure. I wouldn't feel as confident that the MDF could withstand the pressures they'll experience.

Then I cout out the interior of the brace as well. Since the template registers off of the holes build into it, it also allows the part to attache to the template for routing with those same holes. This is faster and much more secure than double stick tape.

And the last picture shows all of the ribs stacked together. It's a near perfect match for the profile on all of the parts.

[BigguyZ]

OK, here are the final pictures showing where I am. I cut the inner front and back baffles for the speakers. The first picture shows how I matched the bevel/ angle from the ribs to the baffle. The second and third picture shows the ribs being placed on the front and back to just get a feeling on how the speaker will look. I'm very pleased so far.

The next step will be gluing the entire internal structure together, and then wrapping the sides with hardboard.

One concern I have is with the baffle glued to the speaker right away, how do I chamfer the inside of the baffle and how do I install the t-nuts for the drivers?

Previously, I'd always build the box with the baffle unglued. That way, I can remove the baffle and work on it until I'm fully realy to glue it in for good.

Thanks,
Travis

[looneybomber]

Because I too am working on curved 4T's and 4cc (but you're much farther than me) the way I figured out how to do it is to do all the baffle work prior to gluing it up. Because yours is already glued, you may have to cut the holes for the driver and use a bit like this.



But not that dove tail bit. You need one that's more than 14deg.

[BigguyZ]

Because I too am working on curved 4T's and 4cc (but you're much farther than me) the way I figured out how to do it is to do all the baffle work prior to gluing it up. Because yours is already glued, you may have to cut the holes for the driver and use a bit like this.



But not that dove tail bit. You need one that's more than 14deg.

I haven't glued anything up yet-I was just testing things out to see how they'd look. The only concern I have with doing the baffle work now, is I don't have the drivers to get precise measurements/ fits from. I was planning on building the cabinets first, then selling my curent Audax HT, then using tha money to buy the kit. Then cut the baffles, then install everything, then do the final speaker finishing...

I may have to rethink my process...

Any other ideas?

[BigguyZ]

Can anyone provide any suggestions? Do I do the cutouts first, or after the whole thing is assembled and I have the kit?

I thought I remember a top mounted bearing chamfer bit, similar to what looney posted. Does anyone have a source for those?

Thanks,
Travis

[ThomasW]

Travis,

T-nuts can be inserted through the driver holes in the front baffle. Use a 'C-clamp' to squeeze them into place.

Any big router bit supplier with have that bit. Try MLCS...

Regarding the woodwork, there's no right or wrong way. Anyone building a factory assembled box does all the work from the outside.

If you have accurate enough measurements go ahead and cut the holes. If there's any doubt wait until you have the drivers in hand.

[Jed]

Jed-
Would the old 1s design match well with the MK2s? I'm open to other designs for the surrounds, as long as they'll match. .

I'd like to explore less costly surrounds. The 1S has been the least built speaker of the Dynamic Series. Many say it is just too big for a surround, which I understand. I wouldn't mind coming up with some kind of wall mounted solution with an RS180 or RS150 and the HDS.

Jed

[BigguyZ]

Well I'd definitely be interested in what you have for surrounds. I have the Recession Buster kit that I plan on making for the surrounds in the meantime, but eventually I'll want to get pair of surrounds that will match the mains.

I looksed for undercutting chamfer bits, and this was all I could find. For $143, I'll probably risk cutting the baffles first- or just do what I can after the fact...

http://www.amazon.com/Festool-492668-Chamfer-undercut-66-5mm/dp/B003KN3W8Q

I looked at MLCS, and it they didn't have such an animal...

[ThomasW]

http://www.google.com/products/catalog?q=%2Btop+bearing+dove+tail+router+bits&hl=en&cid=14369959178085345741&ei=mPVSTPjbFZqkiAT_pYygAg&sa=title&ved=0CBkQ8wIwAzgA#p

[---k---]

Is this just for the driver relief? Just use a rasp and do it by hand. It won't take that much effort. You can buy a cheep one at HD or Lowes. Woodcraft or Rockler will have better ones.

[BigguyZ]

Is this just for the driver relief? Just use a rasp and do it by hand. It won't take that much effort. You can buy a cheep one at HD or Lowes. Woodcraft or Rockler will have better ones.

Oh duh, I should know better than that. Yeah, a rasp will definitely work. Trust me, I have a good collection already...

Well then, I'm hoping to have the "ribcage" glued up this weekend, realy to start having the hardboard sheets wrapped around...

Thanks!

[---k---]

I guess it is because I grew up near Amish country.
Glad I could help.

[looneybomber]

I'd like to explore less costly surrounds. The 1S has been the least built speaker of the Dynamic Series. Many say it is just too big for a surround, which I understand. I wouldn't mind coming up with some kind of wall mounted solution with an RS180 or RS150 and the HDS.

Jed

Jed, after finishing my 4cc and 4T's, I was going to build the 2T's as my surrounds. What are your thoughts on that lowish (for a surround) tweeter height?

Is this just for the driver relief? Just use a rasp and do it by hand.

Oh I feel dumb now.

[Jed]

Jed, after finishing my 4cc and 4T's, I was going to build the 2T's as my surrounds. What are your thoughts on that lowish (for a surround) tweeter height?

You could build them taller for your specific application as long as the critical dimensions near the mids and tweeter remain close.

[BigguyZ]

OK, so I have the skeleton built up completely for one speaker and almost completely for another (you can never have too many clamps, and I didn't quite have enough).

The next step will be to wrap it with hardboard. How flexible is 3/16" along a 4'+ length? Should I do 4 layers of 3/16", or 6 of 1/4" for ease of installation?

Thanks!
Travis

[looneybomber]

I don't know what radius of a curve you have, but I have been looking at 1/8" hardboard and 1/4" MDF and 3-ply. The 1/8" will easily make my curve. I have yet to see if the 1/4" mdf will make it without cracking. The hardboard would make me just as nervous as the MDF. 3/16" should be ok.

Just wondering, but did you mean 4, 3/16" or 6, 1/8"? Because that equals the same 3/4" thickness, where-as your original "6 of 1/4"" would be 1.5" thick.

[BigguyZ]

I don't know what radius of a curve you have, but I have been looking at 1/8" hardboard and 1/4" MDF and 3-ply. The 1/8" will easily make my curve. I have yet to see if the 1/4" mdf will make it without cracking. The hardboard would make me just as nervous as the MDF. 3/16" should be ok.

Just wondering, but did you mean 4, 3/16" or 6, 1/8"? Because that equals the same 3/4" thickness, where-as your original "6 of 1/4"" would be 1.5" thick.

Yup, you're right. I meant (4) 3/16" or (6) 1/8".

It's not a super drasctic curve, but it is over a long length, so that's why I'm concerned. But you're right, it probably won't be a big deal either way.

Thanks!

[BigguyZ]

Well, I looked into what I should use to wrap the skeleton, and after seeing the price of bendy ply and trying 1/4" MDF, I think 1/8" Hardboard is the only way to go. I'm concerned about how well veneer will adhere to it, but I'm doing a test right now and should see tomorrow how it's sticking. Of course, only time will tell. But I hope to get an idea at least.

I still have to post the pics of the glueup for the ribs. I hope to have time tomorrow night to do so.

Travis

[looneybomber]

If your hardboard is like mine around here, there's a real slick side. I was thinking it would have to be sanded in order to get glue to hold to it properly.

[BigguyZ]

OK, so I haven't had much time to work on these, so there's been little progress. However, I still have some updated pics of the initial glue-up process. I have one side on one of the speakers and already I've learned something.

- Cauls are absolutely necessary, and make sure they're long enough.
- curved cabinets are a pain to clamp up.
- Staples, even to keep things in place, will not work. The hardboard pulls right through them.
- I probably should have used Gorilla glue rather than TBII, as any small gap where the sheet doesn't quite fit to the ribs will be filled in. I'll use gorilla to attach the other 3 initial sheets. Though after that I'll use a thin layer of TBII.

I can't wait until these are done! I just need lots more time in my shop, and since I don't live where my shop is at the moment, that's an issue.

[BigguyZ]

more pics

[BigguyZ]

Last one. The parallel clamps were really a help, and I wish I have a lot more.

[godzen]

Great progress...Looks really nice so far

[looneybomber]

Where are you putting your crossovers? I'm at about the same stage you are with my square boxes and am wondering where to put them. I want them flat, but I don't have enough room to put both the MF/HF crossover and LF crossover on the bottom.

[Jed]

The standard crossover fits well on a back wall/side. As long as you have the inductors several inches away from the woofer magnets you are fine.

Jed

[looneybomber]

The standard crossover fits well on a back wall/side. As long as you have the inductors several inches away from the woofer magnets you are fine.

Jed

I have the upgraded XO's with Clarity caps.

Image not available

The caps on the woofer boards are loose and one's even come unglued. I'm going to reinforce them with more glue and some zip ties, but because of that, I'd like to keep my boards flat if possible. Although I was thinking of putting the MF/HF board 90º between one of the woofer braces, attached to the side wall.

[Jed]

I have the upgraded XO's with Clarity caps.

Image not available

The caps on the woofer boards are loose and one's even come unglued. I'm going to reinforce them with more glue and some zip ties, but because of that, I'd like to keep my boards flat if possible. Although I was thinking of putting the MF/HF board 90º between one of the woofer braces, attached to the side wall.

Yup, since you didn't get those crossovers from me directly, and they were shipped a few times you might want to look it over really good and use an epoxy glue to reinforce the hot glue (used on the earlier production boards). The new boards for the MK2 are built on circuit boards and glued with GOOP. They never come loose.

Jed

[BigguyZ]

I have 4 sheets of 1/8" glued to one side for the first speaker. Only two more sheets to go, then it's on to the other side, which has one layer so far.

I'm using a LOT of glue to laminate the sides. The toughest part of the keep the layers aligned, but I'm thinking I'm going to end up having to fill in some gaps with Bondo. I'm also slightly concerned with gaps in the layers. Even with cauls and 4 band clamps there were some small voids. To combat that I've switched from Titebond II PVA glue to Gorilla poly glue. The thinking is the foaming action will expand and fill any gaps in the lamination. I think overall it's still going to end up being quite rigid (I'm hoping- it's a lot of work to get this far!).

As far as the crossover boards, how big are they? Since the sides are curved, I'll either have to mount them with standoffs, or on the bottom of the cabinet.

[Solid7]

I'm using a LOT of glue to laminate the sides. The toughest part of the keep the layers aligned, but I'm thinking I'm going to end up having to fill in some gaps with Bondo. I'm also slightly concerned with gaps in the layers. Even with cauls and 4 band clamps there were some small voids. To combat that I've switched from Titebond II PVA glue to Gorilla poly glue. The thinking is the foaming action will expand and fill any gaps in the lamination.

I use a paint roller and Elmer's when I laminate sheets. As far as alignment goes, are you leaving overlap to route flush? If so, you shouldn't have any issues with either alignment, or squeezeout. (which of course you have to be more careful about with zero overlap and your choice of glue)

One other method you may consider - once you have the first layer on, what about using screws to secure subsequent layers? YOu can back them off with each iteration, and then into the next layer as you lay it down, applying evenly distributed clamping. Before you apply the final layer, pull the screws, and drill out the holes, and plug with dowels. Or just plug and flush the dowels, if you are going to veneer.

[BigguyZ]

That's a good point. Originally, I tried using staples, but the material is so thin it went right through. But at this point I could srew through the cauls, and into the lower layers... I'll try that!

[Solid7]

That's a good point. Originally, I tried using staples, but the material is so thin it went right through. But at this point I could srew through the cauls, and into the lower layers... I'll try that!

Yep, you got the idea. Some sort of firring strip, or even sheet metal strips with machine screws, if all else fails.

I think you will find a higher degree of success with that method. Just be aware that it does represent a higher degree of labor intensity... But I'm guessing at this point, you understand the trade-offs of curved cabinets. :B

[looneybomber]

Bigguyz, depending on how robust your bracing is, have you tried sand bags? You'd need to use just a few screws to align things and to make sure they stay put, but the sand bags will easily take on that curved shape and apply even pressure. 300lbs should hold those sheets down fine, but have another 100-150lbs on standby just in case.

This doesn't show all the weights I have used, but gives a good idea of how I "clamp" things.



Right now I have about 300lbs sitting on my 4T tower because that's all the weight I had here.

[looneybomber]

As far as the crossover boards, how big are they? Since the sides are curved, I'll either have to mount them with standoffs, or on the bottom of the cabinet.

What kind of circuit boards do you have? I have the standard XO's on PCB and can measure them if you want me to.

[Hdale85]

As long as you aren't blocking too much of the brace openings you can mount them on one of the cross braces. I think on mine I mounted the mid/tweet crossover on the underside of the mid/tweet chamber. The woofer board is at the bottom.

[Jed]

The 4T MK2 boards with double matrix and matrix boards are 5.5X5.625 and 5.625X11 (mid/tweeter section). They fit through a woofer hole of 5.75". They are usually mounted on the bottom for the woofers, and a side or back near the mids.

Jed

[BigguyZ]

Thanks Jed! I needed the initial front baffle for support the braces, but once the sides are completed I should be able to take that off. Then I'll have access to the inside for the foam and wiring.

The sand bad idea isn't bad at all. Where does one buy sandbags? HD? Menards?

[Solid7]

The sand bad idea isn't bad at all. Where does one buy sandbags? HD? Menards?

Seeing that you are a DIY'er, one doesn't necessarily need to "buy" a sand bag. (it is just a bag of sand, after all)

Just remember that sand bagging on curved surfaces may not give you sufficient or constant pressure, if you are both bending and squeezing out. The screws are still your best low budget alternative, but I understand that it may be more work than you want to get into.

I hope that whatever you choose provides good results. Like yourself, I can't ever quite seem to be content with square boxes.

[Hdale85]

I used heavy duty cargo straps that you can buy all over to clam the sides. You may have to make a piece of wood that has the same curve profile as your enclosure to put between the strap and the side to evenly distribute the force.