Baltic Birch

[Mark_1042]

What grade is typically used for speaker cabinets and where do you get it? I see that Woodcraft carries grade BB/B, I also found a seller on Amazon that carries the same stuff at a slightly lower price. Woodcraft indicates that BB/B has one face that may contain patches and knots - is this acceptable for speaker cabinets? (provided there are no voids or loose bits anywhere?) Alternatively, are there any other types of plywood you can use?

The local Menards also carries Baltic Birch in grade BB/CP or something like that - didn't look too bad but it had quite a few knots in it.

Right now I'm leaning toward doing a CLD enclosure, a curved cabinet made of 1/8" thick layers, using hardboard for the damping layer. Maybe 2 layers of plywood, 4 layers of harboard, then 2 more layers of plywood for an overall thickness of 1".

[agrippa]

I have heard some having problems with doing layered curved speakers. Many prefer kerfing. Some use other methods. There are tons of designs, on this site, that document how they make curves. As I have been saying it seems like curved is the new square/rectangle.
As far as wood goes. I use MDF and birch 3/4" plywood from HD or Menards. It isn't as good as some but it is cheaper. I think it is abround $45 a sheet. Depending on the design. I will sometimes use two layers(standard box designs) of it or one 3/4" layer with a 1/4" or 1/2" layer. Depends.
Get a mask for mdf. it is bad stuff. In fact my wife bought me the best sander in the world... a festool sander with vacuum. No dust and no need to use a mask. I still use one though. That sander has made me enjoy sanding...wow.

Research

[Mark_1042]

I have seen a couple of people who ran into some troubles building curved cabinets. This is the best thread I've found, which seems to cover most of the hang-up's:

http://techtalk.parts-express.com/showthread.php?t=230233

Some of the links in that thread are very helpful, one of them includes a jig which can be used to attach the layers - seems like the best way to go. (and hats off to the author of that thread, very helpful in covering a lot of the problems one might run into).

But in reading up on materials, I found a thread at DIY audio that seemed to indicate baltic birch was the best plywood to use because it is free of voids and has a relatively stable moisture content. Although other people seem to be using other types of plywood without any issues.

[agrippa]

I had another thought this morning. If your goal is eliminating those out of phase waves by making a box that doesn't vibrate. Then you should focus on Damping as best you can. In fact it is more important then bracing(still important). In Vance Dickason's cookbook he mentions using roofing felt for some of his damping. Some people will use an unglued layer between layers 1/4" or 1/8" hardboard/plywood. If you do this don't glue the felt otherwise it gets hard. Of coarse use your favorite damping material as well on the inside.

Yeah... the post about Curved is good. Stay away from HF clamps. I have broken a few also. Buy American or German.

well I am out of time...

[Mark_1042]

Thanks agrippa, I'll look into the things you mentioned.

I thought that a constrained layer of MDF/harboard also acted as a damping layer? I am wanting to use MDF but am having some trouble finding it in thinner sheets (1/8" or 1/4"). I was also looking at Green Glue for damping but it looks like its a little more money than I wanted to spend.

[Face]

Yeah... the post about Curved is good. Stay away from HF clamps. I have broken a few also. Buy American or German.

Or Canadian...Bessey .

[gmed]

Check out Rockler. you may have a local store.
If you are using it for a simple enclosure, it doesn't matter if you have one side with patches. B/BB is acceptable. Im my experience, even if you have patches, once you stack them, you wont be able to tell.
I have been working with BB ply for years, and B/BB is great.

http://www.htguide.com/forum/showthread.php4?t=30964&highlight=gmed

http://www.htguide.com/forum/showthread.php4?t=32517&page=2&highlight=gmed

[PMazz]

Kerfing any panel product is not recommended in speaker construction. Talk about voids....

[Mark_1042]

Check out Rockler. you may have a local store.
If you are using it for a simple enclosure, it doesn't matter if you have one side with patches. B/BB is acceptable. Im my experience, even if you have patches, once you stack them, you wont be able to tell.
I have been working with BB ply for years, and B/BB is great.

http://www.htguide.com/forum/showthread.php4?t=30964&highlight=gmed

http://www.htguide.com/forum/showthr...highlight=gmed

Wow, that's some nice work there gmed. Very classy. :T

It looks like the nearest Rockler store is a bit of a hike, about 150 mi. I talked to a guy at the local Woodcraft store yesterday and he said they had all sizes of BB, but that they didn't "grade it out." Not sure why, the stuff on their website is graded. So I'm thinking I'll have to go there, or perhaps order it online.

Speaker components should be arriving from PE sometime soon. So hopefully I'll be posting a build thread shortly, or at the very least have some plans to put up.

Cheers.

[agrippa]

Kerfing any panel product is not recommended in speaker construction. Talk about voids....

true. The ones that kerf fill with putty before bending and glueing. Lots of work and mess.

I have seen some that build a typical box and then put a 1x2 or 2x2 on the side(middle usually). Then curve a thinner (1/8" or 1/4") plywood over it and fill the void with sand. It doesn't have the advantage of being curved, its mostly about looks but the dampening is great.

Others will put curved pieces on the inside of a typical box (back mostly) and back fill that void with sand (back heavy)or other dampening material.

I like to make a small void in the bottom and fill with sand. Good ballast and dampening.

The bottom line is make a box that is as sound dead as possible. Wilson's speakers are unbelievably heavy but are about as dead as you get.

I could make mine like that but that isn't practical. have fun.

[agrippa]

Rockler clamps are also good... I thought Bessey was German. Oh well. Get quality if you plan to make other speakers or other things. Cheap ones are fine if this is a one time thing.

[---k---]

I've always got good ply from Menards. Just dig through the stack to find ones that look good.

[mattsk8]

I think I would only use the baltic birch if I wanted to stain it, but even that would be a really tough build. You'd have to 45 all the corners plus you wouldn't be able to do roundovers or anything. Otherwise I'd say use MDF for sure and paint it or veneer it. MDF is way cheaper and delivers equal, if not better, speaker cabinet qualities. I'm not sure why guys use baltic birch; it warps and it's more than double the price. That being said, if you're set on using baltic birch I've used the Menards stuff quite a bit for drawer boxes and found it to be (for the most part) void free and nice wood compared to the baltic birch at other suppliers, plus it's cheaper at Menards.

Agrippa, I also have some Festool sanders and the dust collector- one of the best tool investments I've ever made!! Virtually no dust while sanding MDF and that stuff was NASTY before I had the Festool. Not to mention how amazing those sanders work anyhow. Was a tough choice between the Festool or the Mirka Cerros but I'm in love w/ my Festools now! Only downside is once you start buying Festool it's a downward spiral! To me, sanding was the bane of woodworking before the Festool, now almost enjoy it 8)

[agrippa]

Yup.... I bought the festool jig saw. it is a dangerous biz

[Face]

Festool saw and router here. If I had the coin, I'd have everything Festool.

[mattsk8]

I have 2 sanders, the track saw and the dust collecter. I almost bought the jigsaw just the other day but had to practice some restraint. I have an older Porter Cable jigsaw and the thing still works really well. The dust collector on the Festool jigsaw would be nice, non-exsitant on the PC and it's amazing the dust and mess a little jigsaw can make. I thought about making a base for the PC that had a 0 clearance blade guide out of 1/4" hardboard but haven't gotten around to it. If I need it any straighter I should just get a scroll saw, plus you can use the Festool jigsaw blades (which are awesome) in any jigsaw.

I think my next Festool purchase will be the domino joiner. That's another one that I'm on the hairy edge of getting all the time but just can't seem to justify it since my other biscuit joiners still work well. I know the domino's tenon joint is miles stronger, but the biscuits have heald so far. Either that or the Kapex. Same scenario w/ that though cuz my Makita still does a great job. Amazing how once you bite into Festool all of a sudden all the other tools you have that worked great are obsolete!

[Mark_1042]

I think I would only use the baltic birch if I wanted to stain it, but even that would be a really tough build. You'd have to 45 all the corners plus you wouldn't be able to do roundovers or anything. Otherwise I'd say use MDF for sure and paint it or veneer it. MDF is way cheaper and delivers equal, if not better, speaker cabinet qualities. I'm not sure why guys use baltic birch; it warps and it's more than double the price. That being said, if you're set on using baltic birch I've used the Menards stuff quite a bit for drawer boxes and found it to be (for the most part) void free and nice wood compared to the baltic birch at other suppliers, plus it's cheaper at Menards.

Yeah, the stuff at Menards does appear to be the best bet. Way cheaper than the BB/B grade and I can't see it having any significant disadvatage when compared to BB/B. Probably more knots but I plan on adding veneer to the cabinets so that shouldn't be an issue. The top layer of the baffle will most lilkely be MDF or hard wood to allow for roundovers.

Warping, as you say, is my only concern with using ply vs. MDF. From what I've gathered from online readings, baltic birch has better acoustic properties, but there seems to be a wide range of opinions there. Wilson Audio has some measurements on their website which show BB to have superior damping properties when compared to MDF, but they don't provide much detail in regards to the test methods used:

http://www.wilsonaudio.com/company_excellence_materials.shtml

I would hope that with proper sealing ply would have a decent lifespan (?)

I also believe my original post was incorrect in stating that a layer of MDF between 2 layers of ply would constitute a constrained layer damping (CLD) system. As Agrippa pointed out, roofing felt is a cheap material which is commonly used for the damping layer. Other materials which I've seen recommended for the damping layer are Silicone RTV, vinyl, or 3mm sheet rubber (used for waterproofing decks?). I've also seen Melamine glue recommended as a substitute for Green Glue, reported to offer comparable perfomance at a fraction of the cost.

Just like me to be up at 3 a.m., researching damping techniques. :B

Cheers.