The Scrappy's:
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Design Goals
Build a cost effective high value speaker using available materials in less than two weeks in order to take it to Iowa DIY
2007. (No sense waiting until the last minute.)

After Wayne and I discussed the available materials and drivers in stock, we determined a small MTM would suffice. Since
we were using scrap wood to build the enclosure Wayne suggested calling them the Scrappy's.

Driver Selection
Due to the time constraints, we were pretty much limited to what we had on hand. After looking at the likely candidates, we
ultimately chose the
Hi-Vi B3N's, and Dayton ND20FA tweeter. Both drivers exhibit excellent performance and their low cost
make them a great choice for cost sensitive projects.
Enclosure Design
This one is simplicity itself: Sealed, with dimensions somewhat determined by the scrap pieces
of oak and cheery Wayne had around. I'll admit, they are well proportioned, and I've always felt
that speakers finished in hardwood are just gorgeous. Certainly if your prefer,  MDF can be
used as well. No bracing is required in an enclosure this small. Wayne ran a nice .5" bevel
around the baffle, but certainly you could do a round over as well.
Continued...
Photo courtesy of Sefferdog
Click for enclosure drawing
Crossover design
After Wayne had built and finished the speakers, they were delivered to be for measurement and crossover design. In
keeping with a high value design, I designed a relatively simple crossover, then went to the crossover 'goody box' to see if I
have the components to build it. The time constraints meant I had no time to order parts, and had to make do with what I
had on hand. As a result, we have two crossover designs: The original design, (as heard at DIY Iowa) made by unwinding
inductors and paralleling caps, and the optional design, which uses standard value components. [Since then, I now find that
PE carries the
1.2 mH Jantzen P core inductor. This value will work fine for the 1.15 mH specd on the original design.]

Regardless, all three designs will be presented here. The optional design may be slightly more forward sounding, with less
apparent bass, but since the original was somewhat relaxed, it may end up sounding more neutral to some. The response
variations of the now 3 different variations are shown below:
Response Variations:
Note that substituting the 1.2 mH inductor has
very little effect. while the optional crossover
raised the response about a dB from around
400 Hz to 2 kHz. At this juncture I'll still
recommend the original design but using  the
1.2 mH inductor.