Bluetooth Cello, Junk Making Music Again!

This all started with electronic recycling day, and someone turned in an old set of speakers.

Somewhere on line I had seen someone who had added speakers to an old upright bass, creating an amazing work of art.

From there I started looking for an upright bass, but instead found a musty old plywood cello.

Here are the materials:
Old set of speakers with crossovers
Beat up student cello
Bluetooth 100watt amp
Speaker mounting foam tape


Tools:
Dremel
Drill and bits
Jiggsaw
Soldering iron
Heatshrink tubing
Heatshrink gun
Compass
tape measure
ruler

Step 1:

So here are the speakers, an old set of Marantz.  The front panels were shredded by a cat and they sounded kind of weak. The speakers were built out of particle board so I figured I would salvage the parts.  Upon inspection, one of the mid range speakers was ripped.

I ordered up a set of mid-range Dayton's from Parts-Express.com, while I was there I picked up some 5.25" Woofers as well, since the cello didn't have space for a 10" woofer.

At this point I thought the project would be passive.

Step 2:

So, this cello.  It came from my brother-in-law.  A student model that was missing a few pieces.  No bridge, no strings, and a cracked neck.

It had been in the basement for 20+ years and had this sort of... smell. That, family of mice kind of smell...

I used a light mix of water and bleach to kill the stink.

Step 3:

Ok, time to start planning out speaker placement.  I cut out some paper circles in the sizes needed.

From there I used a compass to mark out holes.

Step 4:

Here is where cello players or luthiers should leave the room!

I drilled holes then used a jig saw to rough out the holes.

Once the holes were roughed out, I used a Dremel Tool with a sanding drum to smooth out the holes to the compass markings.

Initially I was planning on having the speakers rear mounted, but without a smooth circle, it just wouldn't look right. So we were going to surface mount.

Step 5:

At this point we did a test fit.  Initially the squarish speaker frames bothered me, but I got over it.  The gold finish on the tweeters however did bug me.

So I used a paper cup to mask off the cones and sprayed the frame black.

The cello is curved, I used some speaker mounting foam tape to fit between the speaker frames and the cello, then tighter things up till it was snug, careful not to warp the frame.

Step 6:

On the back of the cello I cut an 8" access hole. This allowed me to reuse the crossovers from the Marantz speakers.  Using a bit of hot glue and some screws, these were mounted inside.

Good solid capacitors and coils. Say what you will about the late 70's, they had some great audio gear.

Step 7:

THEN Parts-Express.com sends me this email. A 100watt BLUETOOTH amp is now available.

Oh man.

It was more than I wanted to spend, just about $130.oo bucks, but the project would jump to a new level of coolness.  Audio from my iPhone via Bluetooth to my cello speaker.

Boo-YA!

Step 8:

ok again, more ripping into the cello.  For those luthiers and cello players still reading.. fair warning.

The best way to say this, is I hogged out the hole.  Due to the proximity of the neck, and the thinness of the material, and then the supporting material where the neck connected to the body of the cello needed a combination of techniques.

Basically I used an xacto blade to cut through the thin material, then the Dremel Tool again to smooth and gouge out the rest.

The scrapes in the finish will sand out.

The end result was the amp sliding right in with a compression fit.

Step 9:

The 8" hole in the back was then re-installed.  I used a couple of scrap pieces of plastic from old laptops, and secured them just inside the cello.  Which gave me tabs to re-attach the chunk from the hole.

Step 10:

So, how does it look?  GREAT!

Big question, how does it sound? Sweeeet!

The original speakers were rated for 200watts, the new amp is 100watts, so we're safe there.

The ability to fire up my iPhone and play some jazz without having to connect to a cable is very cool.  I'm already thinking how this could be used in a stage performance production.

The student cello could have been repaired, probably, but it will get used now, verses being a nice looking mouse house. The plan is it will lean in the corner of the office, and the computer speakers on the desk will disappear.