Curvy Speaker Experiments

[gdmoore28]

After building a pair of small curved cabinets for no other reason than to see if I could do it, I decided to experiment on a larger scale using some drivers that I already have on hand. These will be three-way speakers utilizing Dayton DA270 10" aluminum cone woofers, Fountek FE85 3" aluminum coned mids, and Vifa 1" soft dome tweeters. The boxes are 1.5 cu ft, slightly larger than the specified 1.2 cu ft for a sealed enclosure.

The boxes are constructed from 3/4" plywood and 3/4" MDF. Building the small enclosures it become apparent that I needed many more clamps, so on these boxes I built a jig that would allow me to clamp over every rib in the enclosure using only a minimum number of clamps. This method allowed me to use only two staples thru the sides to hold them straight while the clamps were applied.

My first inclination was to build two of these jigs so that I could glue both sides at once, but the first one nearly exhausted my supply of scrap MDF and took up so much time that I decided to do one side at a time.

Here are some pics of the small enclosures I built, followed by pics of the larger ones.



GeeDeeEmm

[lowpolyjoe]

Re: Curvy Speaker Experiments

Looks great. Is that Masonite / HDF that you're pressing for the sides? I'm hoping to do some curve builds with that material at some point.

Those harbor freight quick-clamps are convenient but I was never able to get much clamping pressure out of them. Hope you're having better luck with them.

Looking forward to more pics

[gdmoore28]

Re: Curvy Speaker Experiments

Looks great. Is that Masonite / HDF that you're pressing for the sides? I'm hoping to do some curve builds with that material at some point.

Those harbor freight quick-clamps are convenient but I was never able to get much clamping pressure out of them. Hope you're having better luck with them.

Looking forward to more pics

Thanks, lowpolyjoe.

Yep, it's masonite, 1/8." As gently as this cabinet curves, I feel quite sure that I could have used 1/4" material. I'll be applying another layer or two, although it's probably not necessary. I have so many backing ribs that there is very little unsupported area.

I agree, that model of Harbor Freight clamps are quite crappy. I broke one of the better ones yesterday. They do not have good clamping force. If the money frees up some time in the future, I'd like to replace all my clamps (except for my pipe clamps) with good quality ones.

I'll post more pics as the build progresses.

I have a question for anybody that might have experience with Gorilla glue - the expanding type. I'm using wood glue for attaching the side panels, but bought a bottle of Gorilla glue today, but I'm wondering about whether that's a good product to use for this application. Will the glue have a tendency to ooze out of the exterior joints? How do you clean it off wood?

GeeDeeEmm

[bobbarkto]

Re: Curvy Speaker Experiments

Nice work. I like the ribs. I too would think the skin can be thinner with that much support. But two layers really makes for a nice dead wall.

Gorilla glue will ooze. That's what it does! ;)
Any opening, any joint, is fair game.

If you are finishing the wood with stain or other clear finish where the wood will show then it's best to keep it off entirely. Use masking tape and paper to cover any areas that might be exposed to squeeze out.
It is very difficult to remove entirely. Anywhere the glue touches it will be absorbed into the wood and will prevent even finish appearance.

If you are painting or veneering...
You can remove the bulk with a scrap of wood or cardboard or something, just sort of scoop and lift it off after it has expanded and set a little bit. Wear gloves!!!
The residue can be scraped/sanded smooth after it dries.


Incidentally, I occasionally use a jig similar to yours. Two sided. But I seldom can glue up both sides at once. Can be used as a veneer press, too. I place a thin sheet of cork covered with wax paper between the veneer and jig when "pressing". Wax paper between the veneer and cork to keep inadvertant glue squeeze out from bonding the cork to the veneer.

[tomzarbo]

Re: Curvy Speaker Experiments

I second what Bob said.

Gorilla Glue foams a bunch. If you can find Tightbond poly glue, it will foam much less, but it still does it. In my opinion, Gorilla glue is the best for gluing the first layer to the carcass. It's foaming and filling abilities are helpful for that first initial bond from the skins to the frame -- especially on smaller builds where it's tough to get inside the box to caulk the seams -- with gorilla glue, no caulking is needed.

And Bob is right, after the glue dries, you can scrape it off, but it will stain the wood if you intend on finishing what you have.

By the way, you boxes look very nice, I like the vertical ribs you used on the heavily curved portion of the box. That thing should be nice and dead when finished. It's cool how dead a thin walled cabinet can get with a curve in it! Nice job, those are beautiful!

TomZ

[bkeane1259]

Re: Curvy Speaker Experiments

I second...wait, third the above about Gorilla glue. It's the sloppiest crap on Earth but it's great for gap filling and for turning your fingers black.

Nice cabinets. You make it look easy and we all know it's not.

[gdmoore28]

Re: Curvy Speaker Experiments

I second...wait, third the above about Gorilla glue. It's the sloppiest crap on Earth but it's great for gap filling and for turning your fingers black.

Nice cabinets. You make it look easy and we all know it's not.

Thanks to all for your comments and suggestions. I decided to go with the Gorilla glue and I'm glad I did. It's working fantastic at filling the miniscule gaps that I didn't even know were there. And it DOES ooze - oh, my gosh! But, since these will be painted I'm not too worried. The ooze cleaned off quite easily with a dry cloth when wet, with a flexible scraper when dried.

I applied the second layer on one speaker yesterday so it could dry overnight, so we'll see this morning how it did.

Next question: I've been very frustrated in finding a good fool proof way to seal this wood before painting. I've tried several brands of automotive primer, heavy and medium fill, sanding between coats, and the MDF, especially, just keeps soaking it up and leaving splotches in the first coat or two of paint - especially when there was a smear of glue underneath. I've tried sealing with polyurethane. It seals excellent, but once hardened it is almost impossible to sand smooth, and doesn't like some paint formulations, especially lacquer.

Any suggestions on what kind of sealer I can use that will seal well, sand easily, and give me a choice of topcoats without worry of reactions? Maybe I'm asking too much.

GeeDeeEmm

[knowledgebass]

Re: Curvy Speaker Experiments

Try (dewaxed/blonde) shellac or a shellac based primer. The general rule with shellac is that it sticks to [nearly] everything, and [nearly] everything sticks to it (I hear poly and waxed shellacs do not play nice). I have used shellac under paint and varnishes, but Zinsser is the shellac based brand I see tossed around a fair amount with regards to shellac primers. You may need to treat the 'end grain' with something different to hide the seams (people use white glue, bondo, fibreglass resin, epoxy...).

Ask a question, get a hundred different answers and twice as many exceptions

[jon96789]

Re: Curvy Speaker Experiments

I use Zinsser BIN Primer... Make sure it is the shellac-based primer and not the odorless which is water-based. Two coats brushed on will seal MDF really good...

[gdmoore28]

Re: Curvy Speaker Experiments

Well, these turned out fine. There are two layers of masonite on the sides, and with all the internal bracing, I haven't been able to discern any appreciable cabinet resonance no matter how much bass I give them. All that's left now is to finish sanding them, seal them, then paint them. I'll probably go with textured white on the cabs with smooth white on the fronts. Thanks to all for their suggestions and advice.



*For anybody who is interested, here's the rundown on the components I'm running: cabinet is sealed with lots and lots of polyester fill. Volume is 1.6 cu. ft. The woofer is a Dayton DA270-8 10" aluminum cone. The mid is a Dayton DA135-8 5.25" aluminum cone. The tweeter is the lovely, articulate, allways-sounds-good Dayton DC28F 1 1/8" silk dome. This tweeter has earned it's stellar reputation.

The crossover is a simple off-the-shelf Dayton 260-150. It crosses at 375/3000 Hz at 12dB/octave. The only problem I've encountered is the wild impedance climb of the Dayton mid/woof. I'll be adding an impedance compensation network to the mid to make it match more closely.

The sound? It's hard to describe sound, isn't it? I listen to pop, rock, and jazz. I love listening to a nicely recorded album on the speakers. The bass is plentiful and tight -- but not at all boomy. The highs are on the bright side, but not enough to be obnoxious. This is the first time I've used the DC28F that it actually draws attention to itself. But I have hi freq hearing loss, so the presence is pleasant to me. The mids are smooth and present, not in your face, well-defined. This is the first time I've used a metallic mid, so I'm growing accustomed to their texture. They are not at all objectional, just different from the paper cones I'm accustomed to.

I would recommend this build combo for the amateur builder. It is quite fun

GeeDeeEmm

[Thumper Tom]

Re: Curvy Speaker Experiments

If you can get us the true dimensions of your boxes and location of each speakers, one of the guys might be able to design a custom crossover for this project. Trust me, there will be huge gains by getting rid of the off the shelf crossover.

[gdmoore28]

Re: Curvy Speaker Experiments

If you can get us the true dimensions of your boxes and location of each speakers, one of the guys might be able to design a custom crossover for this project. Trust me, there will be huge gains by getting rid of the off the shelf crossover.

I'd love that. Obviously. I'll post dimensions and specs as soon as I get the time.
GeeDeeEmm

[kenmcculloch]

Re: Curvy Speaker Experiments

GD!!!! What a great build!! Looks great.

This is perfect timing. My next project on the board is a large (49" tall x 14" wide (at front) x 17" deep curved side speaker. I've been playing with different curves but you're look great (I used to tell all the girls that in college!!) Seriously, I was planning in my head to use 5 identical front to back curved braces and use 3/8" bendable plywood (two layers with possible open weave tool box liner in between with glue) then cherry veneer over that. I might use your method of the 1/8" or 1/4" Masonite.

Your clamping jig is also a great idea. I assumed you use the scrap off the curved cutout for the jig? Did you have trouble with the clamps holding on the curved back side?
Question. How did you layout your side curves? I'm trying to optimize the interior cf for the two 10" woofers that will be in these. I've used some curved pieces I had laying around but still not what I want.

Did you put any damping material on interior walls? I've used the Home Depot peel and seal stuff in my current build.

Any help is appreciated. Great Job!!

[gdmoore28]

Re: Curvy Speaker Experiments

GD!!!! What a great build!! Looks great.

This is perfect timing. My next project on the board is a large (49" tall x 14" wide (at front) x 17" deep curved side speaker. I've been playing with different curves but you're look great (I used to tell all the girls that in college!!) Seriously, I was planning in my head to use 5 identical front to back curved braces and use 3/8" bendable plywood (two layers with possible open weave tool box liner in between with glue) then cherry veneer over that. I might use your method of the 1/8" or 1/4" Masonite.

Your clamping jig is also a great idea. I assumed you use the scrap off the curved cutout for the jig? Did you have trouble with the clamps holding on the curved back side?
Question. How did you layout your side curves? I'm trying to optimize the interior cf for the two 10" woofers that will be in these. I've used some curved pieces I had laying around but still not what I want.

Did you put any damping material on interior walls? I've used the Home Depot peel and seal stuff in my current build.

Any help is appreciated. Great Job!!

Hi Ken,
Sorry taking so long to reply. The jigs: yes , I did use the scrap left over from the original top and bottom cutouts. Four jigs per panel seemed to work fine. And, yes, there was quite a bit of serious wrangling to make the clamps hold the jigs in place on the curved sides. The ideal solution would be to make two jigs, one for each side, the second jig used primarily to make clamping easier. I ended up stapling 3/4" square strips of wood on the hangover edge of the opposing side and anchoring the clamps on to those.

One thing I would have done differently would be to make the cross-bracing in the jig from solid wood rather than plywood and mdf. The plywood cross braces were not too bad, but the ones using mdf presented a number of problems, including bending and less-than-solid joints. Neither the mdf nor the plywood held the nails as good as solid wood.

As far as laying out the side curves, I simply cut the front and rear baffles, laid them out on butcher paper with the depth I wanted, then hand-drew the curve i wanted. (I didn't start the curve until a few inches from the front baffle - it just looked better that way) I then transferred the curve to paper, then used the paper pattern to create a pattern from 1/4" masonite. Then, of course, I used the masonite pattern to transfer the curver to my 3/4" plywood tops and bottoms. i've never used "bendable" plywood, but that product would be essential to curving a panel as thick as 3/8." I tried 1/4" plywood at first, but just was not satisfied with the resulting look. It seemed to bend in recurring patterns of flat, curved, flat, curved, etc.. I don't know why that happened. But working with the 1/4" masonite was a real breeze. It's extremely dense, but very easy to bend -- and the curve is consistent from front to back. Once I had 1/2" thickness after two layers, it became obvious that that thickness would be more than sufficient due to the number of internal braces I had installed.

I don't know what to tell use about using the open-weave tool box liner between the layers. I don't think that adhesion or rigidity will be a problem due to the fact that your adhesive will fill the open weaves. It sounds like a good plan, though, because you will be breaking up the natural transmission of sound thru the sides. You could easily do a test mock-up of this configuration and test it side-by-side with a simple two layers glued directly without the liner material.

I initially used a large quantity of polyester pillow stuffing in the cabs, but it simply sucked the bass out of the system. I later removed all of the stuffing and that made the bass kick in very hard. These woofers are crossed at 500Hz, and I think the combination of low crossover point, very narrow back baffle (6"), and curved sides prevented any problem with back waves in the cabinets. I would just experiment with the type and quantity of stuffing until you get the bass response you are looking for.

(Just out of curiosity, which drivers are you planning to use? Will you be using an off-the-shelf crossover or build your own? I hope to later build a custom crossover for these -- just as soon as time and money permits. I think there's a lot of potential with these drivers that could be exploited with a REAL crossover.)

Be sure to post picks and updates of your progress on this project. You can be sure there are dozens of forun members who will be curious about your idea. I think it's a good one.

GeeDeeEmm

[kenmcculloch]

Re: Curvy Speaker Experiments

Thanks GD. I just finished a 3 way with two 10" woofers, mid horn and tweeter horn using an angled side which was a pain to do. Pic attached. Swore I'll never do it again. Connecting two pieces of cherry veneer on 45degree angle isn't my forte. So the curved side is the solution using one not two pieces of veneer. The 3/8" bendable plywood will bend to a 20" circle. Here's a pic of a round sub I built using a paper tube with one layer of the ply then etimoe veneer.

The project I'm about to start will be another 3 way with 2 Klipsch 10" K-1089AV woofers, mid horn and tweeter horn with compression drivers similar to the pic. this will take some crossover building skills and testing. This should be a Klipsch RF7 low end with low midrange xover and a tweeter added. basically a KLF20 with copper colored woofers.

I appreciate your advice on this. I may use some strap clamps from Harbor Freight also. I've used the mesh method before and it does dampen the vibrations. Actually used it in the round sub with carpet adhesive that I spread with trowel.