Chromecast Audio Speaker V2

Following the relative success of my first ChromeCast Audio speaker, I have decided to build another. Despite not getting around to finishing off the cases, both the original prototype and a second production speaker have been in almost daily use. Both sound good for the price of the speakers, with the original prototype sounding nicer to my ears, mostly because of the slightly larger drivers (5.25" vs 4") and a slightly large box volume. I have uploaded a video of the production speaker to my you tube channel DIY Home Build Multiroom Speaker where I discuss the build.

As mentioned in the video the new version will utilise the aclaimed Overnight Sensations design by Paul Carmody. I am hoping this will give a significant increase in sound quality. Paul's design uses the Hivi B4N woofer and Dayton Audio ND20FA-6 tweeter

Hivi B4N and Dayton Audio ND20FA-6

Hardware

I am sticking with the 15W per channel TA2024 amps , mostly because I bought several already, and they sound fine.

12V 15W TA2024 Amplifiers

Revised Design

This time I designed the enclosure in Autodesk Fusion 360. I have opted for a more adventurous cabinet shape, which will again be constructed from slices of 1 inch MDF. Unlike the first design I will be separating the woofer chambers and using Fusion 360 I was able to determine that I need 8 x 1 inch slices to obtain the 4.5 litres volume per chamber required by Paul Carmody's design. I am hoping the finished speaker will look like this.

New design rendered from Fusion 360.

One of the issues with the construction of the original cabinet was making the MDF slices the same shape. Using Fusion 360 to model the cabinet design I have been able to 3D print a router template so that all the slices are exactly the same size and shape. I had to print this in 3 pieces that were then glued together.

3D printed template

Using the template I marked out the cabinet shape on the MDF slices.

Marking out using the template.

I rough cut the MDF slices using a bandsaw, drill, and jigsaw.

Rough cut MDF slices

Then I attached my 3D printed template with double sided tape and used a flush cut bit in my router table to trim the slices to their finished shape.

Flush trimming the MDF slices

The finished slices turned out really nice..

Rough cut MDF slices

Next was glueing the slices together to form the speaker cabinet. This was actually quite a pain, as the slices kept sliding around on the glue. I ended up glueing just one slice at a time and using some weights to hold them in place. Glad the weights came in useful for something!

Glueing the MDF slices together to form the speaker cabinet

I then planed and sanded the cabinet.

Planing and sanding the cabinet.

The cabinet was cleaned with a tack cloth to remove any dust and then I applied paint to the cabinet with a roller. I used a product called Tuff Cab from Blue Aran, a specialist speaker company located about 5 mins from where I work. Tuff Cab is a specially formulated speaker cabinet paint that dries to a hard wearing waterproof surface. It requires no sealing and is applied directly to bare wood/plywood/MDF. With a small roller it is easy to apply and leaves nice uniform surface.

Painting the cabinet with Blue Aran tuff Cab.

Once the first coat is dry I will sand it to further elininate the slice joints. Very pleased so far.

Planing and sanding the cabinet.

After several more sessions of painting and sanding I managed to get rid of most of the visible slice lines. I bought a random orbit sander which made a massive difference to the quality of the finish.

Finish painted case.

I then turned my attention to the front panel. I glued a layer of 5mm acrylic between 2 layers of cherry to form the front panel. I used 2 part epoxy to glue the layers together. The acrylic will be lit from behind by LEDs.

Glued up front panel blank.

I then used my 3D printed template to mark the outline of the front panel.

Front panel marked using 3D printed template

I then used my router to cut out the woofer speaker holes. The tweeters were drilled with a forstner bit. Off camera I reattached the template and cut the panel blank to finished size, again using my router table and flush trim bit.

Routing out the speaker holes

Using Forstner bits I drilled out the holes in the rear panel for the bass reflex ports.

Drilling out rear panel bass port holes

The bass reflex ports are also 3D printed to the precise length described in Overnight Sensation design. These fit the holes in the rear panel very tightly.

rear panel with 3D printed bass ports

Off camera I completed the front panel by chamfering the woofer and tweeter holes on the router table. A quick dry fit gives a better idea of what it will look like.

dry fit of panels and case

More to come soon

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