sourcing void free plywood

[Guest " "]

I like the multi layer cabinet grade plywoods such as birch, oak, and even the maple plywood with the birch top layer.

The best looking cabinets I ever made were K-horns made from mahogany plywood, hand rubbed with tung oil, purposely using very fine steel wool to add an oxidized tone to the finish. The edges were not covered with veneer strips. They were steel wooled until they looked smooth as glass, like the edges of the old school chairs of yester-year that were made of bent cabinet grade plywood.

[dtel]

Jorjen:

I've built several Klipschorn bass bins using 1/2 inch mdf. How many have you built?

You must be kidding 1/2 inch , i must have heard wrong 1/2 would be a joke for a Klipschorn bass bin, don't waist your time .

Sorry i kept thinking 1/2" as i read through the rest of the thread, had to say something.

[JJkizak]

I don't like MDF because it warps under pressure---set something (amplifier) on a shelf made of MDF and 6 months later it is warped and looks terrible---. There are many forms of MDF and it is very confusing. Some manufacturers add ground up metal particles which tear up saw blades. The klipsch use of MDF I believe is very well thought out to prevent warpage with the panels supported with angle blocks and the reccommended glues. Some glues are waterproof and some are not. The house behind where I live ($2,000,0000.00) used MDF support beams (6" x 18") but when it came push to shove they installed steel beams. The floors were MDF 12" trusses 10" apart with 3/4" tongue and groove MDF glued to all areas with waterproof glue. After a few rains there was some raising of the edges. I have videos of the house during construction. My HDTV and regular tv sit on cheapo MDF cabinets and yes they are fully warped. My 4 computers sit on an MDF desk (1" thick MDF) and yes it is fully warped. I have several MDF boards leaning against the wall in my closet and yes they are fully warped. I had to add a huge amount of plywood support and steel angle braces to support the HDTV cabinet. The TV weighs 205 lbs. So you are correct, I do not like MDF at all but I tolerate it.

JJK

[Jay481985]

maybe your a warped kinda person? []

[JJkizak]

I do have my warps. If I could change the vibrational state of the matter in the MDF I could listen to the K-horns in multiple dimensions and multiple universes.

JJK

[bluesboy]

The interior parts of Klipschorn bass bins have always been constructed from 1/2 inch material. The way I understand it they used to use marine grade plywood but now MDF is used because it is absolutly void free and can be had at a fraction of the cost. Another thing that guys want to make a big deal about is that old K-Horn bass bins were glued and screwed together. The only reason they used screws was because they didn't have nail guns. The glue is what gives the joint it's strength.

[Clarence]

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[HarleyMo]

If my memory serves me right, there is a picture of a Khorn being built in the pictures section that is from last years pilgramage. And if my memory serves me right it was being constructed from plywood. Did they change to mdf between last year and this year?

Harley

** EDIT **

I knew alltimers hadnt set in yet. Hope visit 9-17-05

[JJkizak]

The mathematics of this thing looks like something out of Mr. Spocks brain. How many times did PWK have to re-do all of those complex miter cuts?

JJK

[HarleyMo]

Im in the process of building mine. Getting ready to put on the oil finish. The angles are wild. But not too bad with the correct measurements, the right saw, thinking through all the cuts repeatedly and alot of patience.

Harley

[jwc]

Guys. I have a question about wood in general and I apologize that is a little off the main point of the thread.

I was considering making a "curve" on one of the side panels of a Bass horn I was piddling with. In that case I would need a "bendable" material to do so. Now I know you can buy bendable 1/8 inch plywood and possibly glue several sheets together.

But how about this. Anyone ever considered masonite. You can get 3/16 inch masonite and layering 4 sheets together will get you about 3/4 inch in thickness. I was "feeling" some of this today at Home Depot and it is pretty sturdy. Couldn't you glue these together and get a "solid" wall of a cabinet with a curve. Any glue recommendations?

jc

[WMcD]

Sorry the picture is not better. It is in the interest of a quick reply.

This a strip of 1/8 thick Masonite left over from making polycylinders.

It will bend to the extent shown. Much more than this and it will snap. It is probably enough for a basshorn sidewall but not a 90 degree bend of a small radius.

As you can see this one-inch wide strip does not require much force to bend - - maybe a few pounds. That is just some clear packaging tape as a bowstring. The problem is that if you have a 30-inch wide panel and want to bend it, the force numbers add up. If you have have a sandwich of six panels, each 30 inches wide, you're talking a lot of force..

I have not tried gluing Masonite sandwiches. I can only think that yellow glue will work.

I have bent and glued bending plywood to form the sides of midrange horns (much smaller than 30 inches wide of course). Yellow glue does work for me. I apply it to each side and spread it thin and even. I let it sit for a while so it is exposed to air. In any event, It makes for a slippery, messy stack.

I use a form to bend the ply around. It is necessary to use screws with washers under the heads to pull it into place.

Overall I'd say you can certainly use Masonite for the walls of a basshorn. Let me suggest it is worth your while to experiment before using it on your final project.

Gil

[Quisitive]

Even though I rarely get involved in contentious subjects in on-line forums (especially this one!!), I really must concur with filmboydoug.

I've been working wood - in all forms and for many different purposes - for over forty years now, so I can speak from the perspective of some practical experience.

The trick to all this is to understand what you're trying to accomplish, and then use the most appropriate material - and more importantly - the most appropriate construction technique.

Furthermore, I haven't seen any mention of the relative amount of flexing for different material choices. Density (e.g., MDF, and I have used *miles* of the stuff) doesn't solve everything, nor does void-free plywood. The density that MDF provides won't do you much good once you exceed a certain dimension. After that, it starts flexing like any other sheet good because it has no lateral strength. Plywood, on the other had, uses veneers laid down in alternating direction - plus glue - to achieve less flex.

As an example, let's look at the Chinese 11-ply sheet goods availabe at your local home center. Yes, it has ply overlaps and some voids, but more importantly, its density is no greater than common 7-ply with birch faces. If you want greater density, go with 13-ply Baltic or Russian birch, which is much denser, and flexes less. The reason it flexes less is due to the fact that it uses birch plies throughout, so it has more density, whereas domestic birch uses interior plies of fir. In addition, the moisture-resistant glue between each ply gives more strength and less flex.

Now. That said, all of these can be used in speaker construction with effective and incredible results if you understand the physicals, mechanics, and construction techniques that they each may require.

For example, on the back of large horns such as Karlson or University S-9s, you can use open-face torsion box construction techniques that increase the rigidity of large surfaces *incredibly*. If you're not familiar with this technique, do a Google search. I have yet to see this construction concept applied in any threads in the speaker forums. Most contributors just go for straight sheet goods and argue about the relative merits of each instead of talking about mechanical engineering approaches to the problem.

Alright, so I know this may be a bit of a rant, but I truly enjoy - and value - the exchange of knowledge that forums such as these provide and it pains me greatly to see someone shut down simply by trying to prove positional authority by asking one of the members "how many of these have *you* done?" That doesn't prove anything. One member may have put together many systems that were just awful, even though they followed a cookbook example to every last detail. Not only that, they may not have understood *why* they were doing it, other than it was conventional wisdom. Someone else may have produced a superlative example exactly once by thinking everything through and carefully applying some innovative construction techniques. Others may be new to the hobby, have lots of enthusiasm and lots of questions, and are simply looking for some guidance and a better understanding of *why* things work.

Forums like this aren't about egos. They're about sharing knowledge. So come on, let's have a little charity, OK?

Because here's one thing I've learned over the years - no matter how smart you may think you are, or how accomplished you may be, you will undoubtedly come across someone who is far your superior, usually when you least expect it and when it will be most personally embarassing.

Chris

[WMcD]

Thanks for the good advice to all of us. Both on the subject of good manners and good construction technique.

A few of us got a little heated up. But things get more heated on the subjects of amps and wire. Smile. In comparison, the discussion above was a tea party.

Reading the thread as a whole, it seems to me that people's positions and the underlying reasons were fairly clear. This leaves the reader to make a rational decision. Actually, I think either MDF or a decent quality ply will work, and work well. Someone used the term "fool". I believe anyone will that with a grain of salt.

If I may comment further on some points. It is somewhat to defend against any implications that we all here exercise more contention than intellect. It does happen, but not too often. Smile, again.

1) My comments on MDF and strenght was not a matter of chipping the edge off a raw board. Rather, I tend to move the heavy speakers around after construction (no veneer applied yet). So pure resistance to rough handling and dings does count with me.

Also, I believe that if someone is not an expert in woodworking, plywood is easier to work with because it is forgiving of mistakes and particularly mistakes with the use of screws at the edge. It is better for this woodworking klutz.

2) PWK wrote about the use of various thickness of ply on the KHorn. He noted that 1/2 inch had better bass perfomance than 3/8 inch. Yup, hard to believe that thin stuff was used by anyone, but in the late 40's maybe it was prevalent. He attributed the benefit to less acoustic loss in flexing of the structure. I would have thought this would drive him to 3/4 inch. Perhaps he tried that last step and did not find an added benefit. We'll never know unless more info becomes available.

3) Generally, the KHorn, LS, Belle, and Jubilee do have box sections (e.g. the dog house and the "ramps" in the first flare) and are quite stiff.

There are people on the forum who have recognized and addressed issues of relatively large panels which resonate to some extent. These are the exterior side walls of the LS and Belle (maybe the dog house too), and the back panel of the CW. These are treated with bracing of various types by the tinkerers.

In my view such bracing should be be enough. I like box sections too. None the less, we're just trying to get the panels to stop resonating at bass frequencies. I'm not sure we need the admittedly superior qualities of box sections. Of course, it can't hurt.

Best,

Gil

[Quisitive]

Gil -

Very good thoughts indeed!

Wish I had made them myself.

You're quite right about choosing material based on skill level, as well.

I once saw a guy carve an absolutely beautiful Chippenale cabinet leg using a hand axe, a couple of rusty old chisels, a claw hammer, and a throw-away paring knife that had been re-ground. Knocked it out in about25 minutes.

Saw another guy in a seminar with a couple thousand dollars worth of specialty tools who was trying to follow the instructor's directions. You guessed it. He ended up with a pile of expensive kindling, many wasted hours, and a heck of a lot of frustration.

Here's the funny thing. You couldn't even talk to the secon guy. Oh well.

But you know, at the end of the day, what's important about this hobby of ours is whether or not we get any personal satisfaction out of what we try. Gettint there is where I think the fun is.

Chris

[Quisitive]

Gil -

Very good thoughts indeed!

Wish I had made them myself.

You're quite right about choosing material, tools and technique based on skill level, as well.

I once saw a guy carve an absolutely beautiful Chippenale cabinet leg using a hand axe, a couple of rusty old chisels, a claw hammer, and a throw-away paring knife that had been re-ground. Knocked it out in about 25 minutes.

Saw another guy in a seminar with a couple thousand dollars worth of specialty tools who was trying to follow the instructor's directions. You guessed it. He ended up with a pile of expensive kindling, many wasted hours, and a heck of a lot of frustration.

Here's the funny thing. You couldn't even talk to the secon guy. Oh well.

But you know, at the end of the day, what's important about this hobby of ours is whether or not we get any personal satisfaction out of what we try. Getting there is where I think the fun is.

Chris

[Erland]

HarleyMo,

Thank you very much for the great picture.
I am in the process of building my first K-horns, and your pic explained a few details I have been wandering about. If you have more of them, please post them.

Thanks

E

[HarleyMo]

Erland,

I got that pic from the photo section here on the forum. It was taken by a forum member on a visit to the klipsch factory. There are a couple more pics out there, just hit the photo tab at the top of the screen and go to klipsch gallery.

Also, I am finishing up my Khorn project and when I am finished I will be starting a thread here and posting my contruction pics. The guys on here always love seeing DIY pics. Good luck with your project.

Harley

[Erland]

Thanks for the advise HarleyMo,

So maybe a pic. of the build of my "Mother of all preamps" project an't out of place on a speaker forum then.

[Guest " "]

""So maybe a pic. of the build of my "Mother of all preamps" project an't out of place on a speaker forum then.""

Let's see it....