Nagaoka advice first project

Dunhas

Member
2016-02-29 1:59 pm
Hi everyone,
I've been following this forum for some time, finally I decide to go for my first project. I have a pair of fostex fe168esigma, and after searching the web I found the map for the Nagaoka D-37 (with great reviews) image.jpeg .
My question is, After seem the map, I believe if Is posible adjust the map to use a router instead plain tables, curve the angles, go for a final slide instead of the table ladder (that most people cover with peebles). Do you Think is a good idea¿? Any experiences? I don't want to compromise the final sound... Any advice in how to do this remaping? (Angles? Etc?)
I believe this is the first step for a loooong project, with mano doubts on the way, but I'm really entusiastic about it!!!!!!!!!!
Any help will be appreciated

Cheers
Daniel
 
Short answer is 'you can -but it's not a good idea.'

Nagaoka-san's horns were deliberately designed using the expanding cascade of straight manifolds / sections. The shifts in cross section and sharp edges through the expansion path are functional parts of the low-pass filter. If you round them off, you will simply improve efficiency at the upper end of the horn's functional bandwidth (upper bass / lower midrange) right where you least want it. Back-horns, like any back-loaded enclosure, are only useful over a very limited bandwidth: 300Hz is about the practical upper limit before you run into problems with excessive group delay etc.
 

Dunhas

Member
2016-02-29 1:59 pm
Thanks scottmoose, point taken!!!
Do you have experience with this cabinet? Do you think it is the best alternative for this drivers?
Also, After some research I found fans for either MDF or MDP, what do you think is the best choice for this project?

Best regards
Daniel
 
Briefly. It's a decent example of its type.

As far as 'best' goes, that rather depends on what you mean by 'best'. All loudspeakers are a compromise, and you select those that most closely meet your particular criteria. About as far as I can go is that the D-37 is one of Nagaoka-san's most successful / highly regarded designs. It has reasonable extension and gain, and a fairly effective acoustic low-pass. It's also reasonably easy to adjust the tuning, for e.g. by reducing the volume of the low-pass (driver) chamber.

Like designs, different materials have different properties & different balances of advantages & disadvantages. I assume by MDP you're referring to plywood?

Anyway, short version: the Nagaoka boxes were designed assuming a quality void-free plywood would be the construction material. In general, for a given thickness, a high grade, void-free plywood like Baltic birch is superior for bass enclosures to MDF. It has greater structural rigidity and is lighter, so its basic resonant bandwidth is naturally higher. The multiple plys and glue-lines also inherently result in greater boundary losses than a more homogenous material like MDF. You can use MDF, but based on typical MOE values you need about 1 1/8in - 1 1/4in of it to equal the rigidity of 3/4in of Baltic birch ply, albeit with much greater mass. That can be a good or bad thing depending on what you're doing. It's OK for typical midrange / HF enclosures.
 
Planning on building my own ON, too.

I have good woodworking skills (cabinets, boatbuilding) so the intricacies do not bother me too much.

But I am a novice on speakers so, some questions, please.

1. The plans (http://p10hifi.net/FH/downloads/SpawnHo ... 070412.pdf) call for 3/4 inch plywood and the spacings take into account plywood that's a full 3/4" thick. But local 3/4" ply are really 5/8". Should I adjust then the cuts so that the cavity dimensions are preserved? Or should I just cut the planks according to plan and just center them where they should be attached (making each cavity slightly larger). Or am I fussing with this too much?

2. The front baffle is sandwiched between the cabinet sides and attached to the butts of the 4 horizontal chamber dividers. I am planning to put some vertical battens on the interior of the cabinet sides sides so I can make sure there are no leaks. Battens would probably be 1/2" tto 3/4" triangular planks. Would these battens mess up the acoustics?

3. To strengthen the joints, I plan to fillet the 90" joints with epoxy putty. Filleting is an old technique in boatmaking. Sort of like having a C-crown-molding made of epoxy. Will this again mess up the acoustics?

4. I plan to sheath (paint) the inside with epoxy resin to make the inside stiff, hence, increase reflectivity. Is this a bad idea?

5. The plywood available in my place are lauan, a tropical hardwood. Appreciate any comments on this wood.