In my country it will be difficult to find "Baltic Birch plywood" just because I don't know how to translate it. 😕 
Here (Brazil) we have 2 kinds of plywood: Standard and other specially to build boats. Would it be the second option?
thanks
Highef
Here (Brazil) we have 2 kinds of plywood: Standard and other specially to build boats. Would it be the second option?
thanks
Highef
In my country it will be difficult to find "Baltic Birch plywood" just because I don't know how to translate it. 😕
Here (Brazil) we have 2 kinds of plywood: Standard and other specially to build boats. Would it be the second option?
thanks
Highef
Up here we also have "marine grade" plywood, which due to the availability and relative affordability of "baltic birch" ply, I've never tried. It would be my guess that it would be the better choice of the two options listed.
What you want to looks for is the plywood with the most plys. As a reference, 18mm BB has 13 plys, 15mm 11, 12mm 9.
dave
oh boy, here we go again
well, no problem in the sense that the drivers will work, but a lot of folks prefer the sound of the BB ply vs other materials
Hi Highef,
Where in Brazil are you? You won't find Baltic Birch ply as such, but you can certainly find stuff here in Brasilia which is probably as good, so most likely you can find it where you are also. You need to find a place that caters to furniture makers (quero dizer, marceneiros) rather than builders, and ask for "compensada" with enough layers, which is void-free, as someone stated above. There is plenty of this stuff made in Brasil so you can certainly find it if you look around. (To be completely honest, when I made my speaker cabinets I used some plywood salvaged from old furniture, but I did check out prices at the lumberyard first so I know it's available, and appeared to be pretty good quality.)
On a different note, since you are looking into Fostex drivers, do you know anywhere in Brasil they sell them? Or will you import? Better yet, do you know of any Brazilian made full-range drivers?
Cheers
Nigel
Where in Brazil are you? You won't find Baltic Birch ply as such, but you can certainly find stuff here in Brasilia which is probably as good, so most likely you can find it where you are also. You need to find a place that caters to furniture makers (quero dizer, marceneiros) rather than builders, and ask for "compensada" with enough layers, which is void-free, as someone stated above. There is plenty of this stuff made in Brasil so you can certainly find it if you look around. (To be completely honest, when I made my speaker cabinets I used some plywood salvaged from old furniture, but I did check out prices at the lumberyard first so I know it's available, and appeared to be pretty good quality.)
On a different note, since you are looking into Fostex drivers, do you know anywhere in Brasil they sell them? Or will you import? Better yet, do you know of any Brazilian made full-range drivers?
Cheers
Nigel
It seems that there were already lots of discussions about it here. Actually is was just a curiosity, I will use plywood.
Nigel,
I live in Sao Paulo and I see you have some expierence in my country, right?
I found several types of plywood here.
How much is the Balty Birch per ft2 or per piece? Maybe I can try to do a price comparison.
I found a very good marine grade ply "Cedro" that costs around US$ 100,00 on entire piece (3.5 m2) and it is 15mm thick.
We have very few fullrange choices here in Brazil. There are bravoxaudio.com.br but it is made for environment sound and I don't know anything about it's quality. We have many brands of other drivers and very good subwoofers. My TL sub has a brazillian driver.
There are no fostex dealer down here. I usually buy it on-line with international shippment. Not only equipment, but music media too.
thanks!
Highef
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Perhaps I wasn't clear. You won't find exactly Baltic Birch ply down here, but you certainly can find something equivalent. I don't know if the marine ply you found is the same as I saw, but certainly there are more than two kinds available if you look hard.
The Cedro ply you found is probably fine. If you can look at the ply before buying just look at the cut edge to see if there are visible holes or gaps - if not, and if the ply is reasonably heavy then it's almost certainly fine. (Neste caso nao ha razao acreditar que madeira do hemisfero norte e melhor do que do sul - madeiras diferentes tem nomes diferentes mas em geral o produto domestico neste caso e muito bom mesmo. Provavelmente muita madeira vendida nos EUA como "baltic birch" de fato e feito em SP de madeira de Manaus...)
It's about 18 months since I looked at price, so even if I could remember it wouldn't be much use to you... If I am near the lumberyards any time soon I will take a look and see how much they are asking per sheet, and let you know. (It isn't near home or work, so I can't promise any time soon.) In any event, I doubt if the price is very different from what you were quoted. If you are going to ask them to cut it for you then it's worth paying a little more to get good work done anyway.
I have looked into Bravox, Selenium et cetera, but you are right - no real fullrange choices. I am interested in the Akron drivers (although not full range, and they are expensive). Do you know anyone who has used them?
Sou ingles de nascimento, mas moro em Brasilia quatorze anos.
Cheers
Nigel
The Cedro ply you found is probably fine. If you can look at the ply before buying just look at the cut edge to see if there are visible holes or gaps - if not, and if the ply is reasonably heavy then it's almost certainly fine. (Neste caso nao ha razao acreditar que madeira do hemisfero norte e melhor do que do sul - madeiras diferentes tem nomes diferentes mas em geral o produto domestico neste caso e muito bom mesmo. Provavelmente muita madeira vendida nos EUA como "baltic birch" de fato e feito em SP de madeira de Manaus...)
It's about 18 months since I looked at price, so even if I could remember it wouldn't be much use to you... If I am near the lumberyards any time soon I will take a look and see how much they are asking per sheet, and let you know. (It isn't near home or work, so I can't promise any time soon.) In any event, I doubt if the price is very different from what you were quoted. If you are going to ask them to cut it for you then it's worth paying a little more to get good work done anyway.
I have looked into Bravox, Selenium et cetera, but you are right - no real fullrange choices. I am interested in the Akron drivers (although not full range, and they are expensive). Do you know anyone who has used them?
Sou ingles de nascimento, mas moro em Brasilia quatorze anos.
Cheers
Nigel
Hey Friends,
I was doing wood researching down here in my country, in a specialized DIY street called "Gasometro" and I found many types of plywood.
The best one (and more expensive but I can handle) is the "Cedro" marine grade ply. It is very solid and void free.
The only problem is that it's available only in the 10 mm or 15 mm thickness. Which one would be preferrable?
I was thinking about adapt the original fonken project and use 10mm so I can do the ports (suggested as 9.5mm) and use two pieces for a 20mm front baffle. What do you think?
I would appreciate any help.
thanks
Highef
I was doing wood researching down here in my country, in a specialized DIY street called "Gasometro" and I found many types of plywood.
The best one (and more expensive but I can handle) is the "Cedro" marine grade ply. It is very solid and void free.
The only problem is that it's available only in the 10 mm or 15 mm thickness. Which one would be preferrable?
I was thinking about adapt the original fonken project and use 10mm so I can do the ports (suggested as 9.5mm) and use two pieces for a 20mm front baffle. What do you think?
I would appreciate any help.
thanks
Highef
If it's not too late to offer an observation,we noticed quite an improvement when we switched from nominal 1/2" to 5/8" ( i.e. 12mm to 15mm) material on our Fonken builds. The port dimensions were specifically calculated to use 9.5mm (i.e. 3/8") MDF for the port spacer blocks. The theoretical difference that .5mm would make in the tuning could probably be swamped by other factors such as type or amount of damping, wire, etc., but as Dave could elaborate, the material was actually chosen to introduce a mismatch of mechanical impedance between the 3 layers that comprise the side wall panels.
I went so far as to thickness plane some BB ply for these spacers on one build, but except for the laminated Bamboo plywood pair that were last domiciled at casa Purvine, have stuck with MDF for this particular part. A softer solid wood such as Poplar, Douglas Fir, Yellow Cedar, etc., could also be deployed.
If you do elect for 15mm, in the interest of material conservation, a single layer for the front baffle would probably suffice.
Hi Chris,
thank you for the answer and it is not too late, I will order the wood pieces next weekend.
Let me see if I understood:
- I will use 15mm plywood and adapt this poject to preserve the internal volume of the cabinet.
- The ports remains with 9.5mm (problems in doing with 15mm? I think I didn't get it in you message). I will try to find some 10mm pieces in furniture makers since I need only small pieces.
- The front baffle will be 15mm thick.
thanks!
Highef
thank you for the answer and it is not too late, I will order the wood pieces next weekend.
Let me see if I understood:
- I will use 15mm plywood and adapt this poject to preserve the internal volume of the cabinet.
- The ports remains with 9.5mm (problems in doing with 15mm? I think I didn't get it in you message). I will try to find some 10mm pieces in furniture makers since I need only small pieces.
- The front baffle will be 15mm thick.
thanks!
Highef
In a word, thicker material for port spacers would not be recommended for this design. Same type of material (i.e. the plywood) would be fine, but if you have any further questions as to why MDF is preferred, or have any other questions, I'd suggest you contact Dave directly.
The use of multiple high aspect ratio of port slots, as well as their lengths was specifically intended to provide a more resistive load on the driver.
In at least one of the smaller members of this family with a single port, we built 2 versions; one with standard round port, and the other with a bifurcated slot on the bottom of the enclosure. The latter showed a distinct advantage in terms of smoother low frequency roll-off and therefore usable extension.
The slot spacer height is critical -- any deviation can dramatically change the port area because of the very high aspect ratio. 9.5mm was choosen for the Prime as it happens to be the thickness of a piece of locally sourced 3/8" MDF.
A material for the spacers that is different from the main carcass, as it will give a more dramatic impedance change across the thickness of the composite side panels. MDF or solid is recommended but Chris has run the same plywood thru
I am revisting all of the Fonken series plans with the idea to make them sufficiently detailed to be able to ask some token amount of money for the plans (even more comprehensive than the recent Lake District plans -- what is currently available will remain available), This will eventually include different material thicknesses and some port size options -- all this to better suit materials found around the world.
I have preliminary plans for 15mm almost done, they will not be available for general release, but i do need a couple beta testers for feedback. eMail me.
dave
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