Aurora

Aurora


Designer:
Matt Doherty

Project Category:
Bookshelf Speakers

Project Level:
Intermediate

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
This pair of bookshelf speakers was designed for hi-fi listening in a close-to-on-axis environment but was also designed to look as good as they sound. These will be in a very visible part of my dad’s home, so the visual aesthetic was as important as the sonic experience. I intentionally did not want to get into the business of “veneering” but would rather showcase the fusion of the beauty of hardwoods and the technology of state-of-the-art drivers in my projects.

Design Goals:
Beautiful natural wood, clarity in sound, unabrasive frequency production.

Driver Selection:
I chose the HiVi F5 woofers and TN25 tweeters due to their compatible frequency ranges and visual interest.

Enclosure Design:
Naturally, lots of factors go into the enclosure design, but as the TN25 tweeters are sealed with a proper enclosure, the only dimension to worry about is the volume as it pertains to the woofer. To determine the size of the box, I first used the “golden ratio” to decide the face dimensions of the front baffle. I then considered the thickness of the material – as all 12 corners were to be mitered – to determine a proper depth of the box. After lots of math (and some spreadsheet work), I was able to appropriately model the build in SketchUp. To accommodate the crossover and dimensions of the rear areas of the drivers, I planned on a 10% decrease in interior box volume which was adjusted by poly-fil.

Enclosure Assembly:
The twelve miters are difficult if you can’t guarantee consistent cuts or thickness of the case material. The bottom part of the box is removable via the rubber feet (with posts installed inside the box for mechanical fastening). The front baffle was carved out on a CNC due to the unusual and specific tweeter dimensions. Images will show the necessary dimensions. The miter keys were installed after the sides were glued up using a table saw and dado stack on a shop-built sled. The keys are decorative, but also support the joint for wood movement and end-grain glue connection.

Crossover Design:
Purchased the Dayton Audio XO2W-3K 2-Way Speaker Crossover 3,000 Hz (Part # 260-144). After pricing the components, the Dayton Audio XO was a better deal, and upon receiving the product, it was very high quality. I recommend this! The panel was hot-glued to the interior of the cabinet in a place that would not interfere with the drivers, binding posts, or vent tube.

Tips & Tricks:
I used a CNC (a learning curve for me; it was my first time), but if you choose a different tweeter, this is very approachable with a Jasper Jig! In fact, I had every intention of using my own router, but ran into problems as I didn’t have bits, nor do I have the shop setup, to get the curved radius correct for the HiVi TN25 tweeter cutout. The CNC was available for free for my use, so I did a YouTube crash course on path writing for CNC routing (and Fusion 360) and it turned out great.

Also, the shop-built key jig (you can search YouTube for ‘spline jig’) was a 30-minute project that added additional detail that more than paid for itself in aesthetic ROI.

Seal the interior and exterior of your hardwood box. There is a product by General Finishes called “Seal-A-Cell” that will go on all surface areas that will not receive glue in the future.

Conclusion:
This is definitely more of a woodworking project than a speaker building project. The wire-up of the crossover to the binding posts and drivers was very straight-forward (I used female crimp terminals and shrink-tubing, and solder for the binding posts). Final assembly only took an hour or so, but the woodworking, truing up the miters, and multiple coats of finish (take time here!) are where the hours disappear.

About the Designer:
Matt is a high school band director and music teacher that pursues more hobbies than he cares to admit. These are his first attempt at building speakers, and will be opening a small custom speaker business. We’ll call these “Aurora”, named after the Roman goddess of the dawn – these are the dawn of what Matt hopes to be a lifetime fusion of what makes him tick: music, woodworking, and science.

Project Parts List:

HiVi TN25 Fabric Dome Tweeter
HiVi F5 5″ Bass/Midrange
Dayton Audio XO2W-3K 2-Way Speaker Crossover 3,000 Hz
Speaker Cabinet Port Tube 1″ ID x 4″ L Flared
Speaker Cabinet Port Tube 1″ ID x 4″ L Flared
Parts Express #6 x 3/4″ Deep Thread Pan Head Screws Black 100 Pcs.
Parts Express Binding Post Banana Jack with 1″ Thread 2 Pair Black Gold
Acousta-Stuf Polyfill Speaker Cabinet Damping Material 5 lb. Bag
Primary Wood – African Mahogany
Secondary Wood (miter keys) – Hard Maple
Finish – General Finishes Arm-R-Seal Satin

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