The project: Build a pair of reference quality speakers to cover the mid and high range of my speaker system. The bass modules are completed, except for the finishing of the maple front baffles. I’ll post pictures when that is complete. The cabinets themselves, for the electronics and bass modules, are from a 1970′s hifi set that belonged to my grandparents. I retrofitted the inside of the speaker cabinets and will put up info about them in a separate post.
Images here:
http://www.webherrera.com/photos/index.php?album=HiFi+Set
For those unfamiliar with the Zaph Audio ZD5, they were designed by John Krutke. Here are the design details:
http://www.zaphaudio.com/ZD5.html
The construction of these cabinets follows John Krutke’s guidelines as far as the cabinet width (within .5″), but I am going to be building a cabinet with curved sides. The front baffle will be rounded over, though with a 7/8″ radius that carries into the 11.25″ radius of the curved sides. It will be interesting to see the measurements of this design compared to Zaph’s original. If I muck things up completely, then I guess there’s always equalization…
As a side note, calculating the volume of a curved enclosure is made very easy by designing with Google Sketchup (basic version is free). I highly recommend the program for working out design issues and planning for the construction.
During the design phase, there was one major problem, pointed out by a friend, and that is wood shrinkage/expansion:
I want a cabinet where the exterior displays 100% real, non manufactured wood (veneer is ok) and I don’t want to paint any part of it, as I’ll be using a hand rubbed finish. If using Zaph’s enclosure parameters exactly, this is problematic because rounding over the top and sides of the front baffle means a veneering task that would exceed my skills, and using hardwood presents additional problems.
Real wood swells and shrinks a significant amount depending on the season and mixing real wood on front with manufactured plywood or mdf could cause issues where the enclosure tears itself apart. In addition, hardwood is a poor speaker building material because it tends to resonate within the audible range more easily than relatively dead, manufactured woods.
So, I knew I wanted a curly maple front baffle, and I got a nice, 1/2″ thick by 7.5″ wide board off ebay:
The solution is to thin the middle portion of the board down to about 3/32″ of an inch to reduce the movement issue – the wood will behave more like veneer at this thickness. That is the hope at least.
The sides will remain full thickness so that they will accept the round-over:
3/4″ Baltic Birch will then be attached to the back. The holes won’t be made until after the birch is attached. I’ll be using the router table with a stops on all sides to rout out the excess wood.
More to come….