Aside from being aesthetically pleasing and unique, using actual tree rounds as speaker enclosures is beneficial to the overall speaker design because it results in an almost seam-free cabinet, thick and acoustically dead enclosure material, and non-parallel internal sides which help to reduce unwanted frequency amplification and reverberation.
This Instructable describes the unique process of how I built these specific tree speakers, and is not meant to be a complete and comprehensive guide to speaker building. For that, please see my Instructable on How to Build Custom Speakers, which the DIY speaker builder working on his or her own project will find much more helpful.
I think that the appropriate question to ask here is not "why build speakers out of a tree", but rather, "why not"?
Step 1: Story
The giant tree's death was unfortunate and sad, but the loss of the tree ultimately led to the birth of something else: The Elm Tree Project. The joint venture between Brown University and The Rhode Island School of Design produced a set of classes, exhibitions and specially designed studios, all built specifically to explore and produce various forms of art that could be made from the deceased tree.
I was lucky enough to be a part of this unique program during my time at school, and have finally gotten around to documenting some of the work that I produced during my involvement with The Elm Tree Project on Instructables.
Step 2: Materials and Tools
- large approximately 14" or greater tree round (preferably dry, but wet is ok, just expect some checking/cracking and damage control)
- (2) 6" woofers
- (2) 1" cloth dome tweeters
- 16 awg audio connecting wire or lamp cord
- extra long binding posts
- crossover components (dependent upon speaker design)
- PVC for speaker port
Step 3: To Plunge Cut or Drill...that Is the Question
Either method would prove to be challenging and labor intensive since I was basically creating a 16" deep and 11" wide bowl out of a solid chunk of wood. Plunge cutting with the nose of a chainsaw is absolutely doable, but can be dangerous because if the top quarter of the bar nose should engage the wood, there's a high likelihood that the chainsaw will kick back. If you've operated a chainsaw before, you know that nose cuts are not something that you do every day and that they can be a bit challenging.
Fearing for my own personal safety, and not being an expert chainsaw operator, I decided to go with the more time consuming, but ultimately safer method of a powerful drill paired with an extremely large carbide tipped auger bit.
Step 4: Slice Off the Backs
The cuts below were made with a chainsaw. The chainsaw bar does remove a larger kerf of material then I'd like, but it was my only real option since most band saw's can't accommodate the rounds +14" diameter.
Step 5: Drilling
I used a very large carbide tipped auger bit (we're way beyond spade bits here since they take too long making dust out of the wood as opposed to larger shavings), and began boring holes into the elm wood, drilling from back to front, stopping approximately 1.5" from the front face of the speaker.
Mark the auger bit with some tape or a zip tie to indicate where to stop so that you drill too far and pop out the front face of the speaker.
To remove the material, I drilled many many holes to create a honeycomb type formation of wood that could then be removed using a hammer and chisel, smaller drill bits to break through the walls, and brute force. Removing the honeycomb structure is truly difficult because it's just so much material, and is connected to the solid wall of the tree round over the honeycombs entire exterior surface. That, coupled with the fact that with the wood was still slightly wet during this process made for some pretty tough fibers that I had to rip through in order to remove the honey comb.
This was by far the hardest part about building speakers made from tree rounds. All in all I'd say that it took even longer to bore out the centers of the tree rounds than it normally takes me to build a rectangular standard speaker enclosure, but, it was well worth it.
The internal volume that I bored out was about a 3/4 of a cubic foot - plenty of air for my 6" driver to move.
Step 6: Cut Holes for Speaker Drivers and Ports
The +5" hole for the woofer driver was too big to use a whole saw to cut, so I traced a line and used a jig saw instead. You could also use a circle jig on a router equipped with a long straight bit to cut the holes for this step if you like.
Step 7: Install Crossovers and Drivers
The crossovers were soldered together according to the speaker kit's wiring diagram and then mounted to Masonite backers using hot glue. The Masonite boards were into place inside the speaker enclosures with short screws.
Extra long binding posts that would stick through the 1.5" thick back cap were installed and then connected using the speaker wire or lamp cord to the crossovers, and then finally to the drivers themselves.
Small pieces of acoustic foam were mounted to the inside of the enclosure in between the Masonite backer boards using finishing nails and glue to hold them in place.
Once everything was wired up and installed into place it was time to put the back caps back into place. I used 8 large 3" wood screws to seal the backs on and complete the enclosure.
Step 8: Make Stands
There is one stand per speaker and they hold the tree speakers at a slight upwards angle towards the listeners ear.
The slices were cut with a chainsaw off of the original stock material branch, shaped on the band saw, and then finally sanded smooth.
Step 9: Finishing
Dutch Elm Disease is caused by a fungus that the elm bark beetle carries into the tree. The bark beetle itself is not what killed this particular elm, but it is the horse that the fungus rode in on so to speak.
The story of the bark beetle's reproduction leaves behind the unmistakable pattern on the surface of the wood that is pictured below. The beetle first burrows through the bark and into the outer flesh of the tree to create the dark line. It then lays it's larvae all along that burrow. When the the larvae hatch, the baby beetles dig and eat their way through the tree's flesh to escape, causing the lighter lines which radiate off of the central dark ones.
Oh bark beetle, I wish you never infected this lovely elm tree in the first place, but I am mesmerized by the beautiful artifacts of your stay that you left behind.
Step 10: Enjoy
The speakers were recently shipped across the country from storage at my folks home in New York to my home in Oakland, CA. They now reside happily in my living room and are my main speakers. Their entry back into my life was the inspiration that I needed to write this Instructable. Hopefully this Instructable will inspire someone else to make a pair of speakers out of something else unique and interesting, and the cycle of creativity will propel itself forward into the future spreading joy and ingenuity.
I'm very proud of them, and to this day, even after all the different things I've made, these unique tree speakers remain one of my favorites.