Little speaker, big sound in this folded horn speaker hack.
I’m not that young anymore (born in 1965, the year of Moore’s law) but I’ve been interested in technology and engineering since I was young.
My uncle Hubert inspired me: he helped me setting the first steps in electronics. He also gave me some old magazines, more than 30 years ago.
The April 1964 issue of the Dutch magazine “Radio Bulletin” contained the building plan of a folded horn speaker (designed by Dipl. Ing. H.H. Klinger), which I built once when I was about 18 years old. It sounded fantastic.
With the release of the IKEA Symfonisk speaker I was wondering if that modern technology could fit in a scaled folded horn. And if it could be hacked in an IKEA shelf. The BESTÅ base element (602.459.62) seemed to be a good match: scaling the design to 49% would do the job.
Initially I wanted to build it using only BESTÅ shelves, but that didn’t work out. IKEA engineered these shelves such that they are light and strong, using a honeycomb structure. So I started over using fiberboard.
Hollow core structure in BESTÅ shelves
I just completed building it and the BoomBESTISK to me now sounds as a Sonos Play 3 while it costs less than a Sonos Play 1. Named it ‘BoomBESTISK’ based on Boombastic by Shaggy, BESTÅ and SYMFONISK. I hope you like it too.
1. Be sure to apply glue/kit between all panels mounted to make all connections airtight. I used screws and glue everywhere.
2. Start building the BESTÅ base element: connect bottom plate and sides.
3. Cut the BESTÅ shelf from 56 cm x 36 cm to 56 cm x 32.3 cm. Mount it vertically at 24 cm from the front of the base element. Use glue at the sides.
I used the cut off part of the shelf at the rear side to fix it.
4. Cut a 20.6 cm piece of the lumber and mount that on the bottom of the base element (yes: glue + screws) at 46.3cm from the left inner side of the BESTÅ base element. Cut a 30.5 cm piece to and mount that onto the rear side. Fiberboard panel f will be mounted at the left side of this L shape.
Building the labyrinth
5. From there the labyrinth is built, from top-right to left. This is a difficult and time consuming part. For panels that are hard to mount firmly, use parts of the aluminum angle bar (20mm x 20mm).
6. Note that I didn’t use panels m, n, o and p. I constructed the wedge using 9 trapezium shaped parts that were glued, tacked and screwed.
7. Drill the hole in the right side of the BESTÅ base element to be able to secure the top plate later on. Avoid damage by drilling with a piece of wood clamped onto the BESTÅ panel.
8. Mount panel f’ at the right inner side of the BESTÅ base element. Cut a 20,6 cm piece of the lumber and mount that on the bottom of the base element, it should neatly fit in. Cut a 30.5 cm piece and mount that onto the panel f’.
9. Cut pieces of lumber that fit on the bottom between the different panels.
10. Cut a 30.5 cm piece of lumber and mount that onto the right side of panel i. Cut a 30.5 cm piece to and mount that onto the left side of panel g.
11. At this time, the only panels left are the top of the BESTÅ base element, the rear panel of the BESTÅ base element and panel d.
12. Drill a 75 mm hole in the rear panel between panels f and f’. This will later be used to feed cables and wifi antennas to the rear.
Do not cut any cable. Be careful: do not damage the flex PCB. Keep all parts. Note: this is an electrical device. Make sure that it has not been plugged in (e.g. to test it) as residual charge can remain on the electronics.
14. Cut out the SYMFONISK front panel with the buttons and LED using a multitool. Then use a saw to make the cuts straight.
15. Mount the SYMFONISK metal cooling plate on a piece of fiberboard (I reused the part that I cut from panel g) using glue & screws. Mount the SYMFONISK electronics panel with 4 screws onto the cooling plate. Apply weatherstrip at the rear of the fiberboard panel.
Connecting the parts
16. Connect and secure the mains cable. Put isolation tape around this too (not shown in the picture). Feed this cable through the 75mm hole in the rear.
17. Connect a network cable to the electronics board. Feed this cable through the 75mm hole in the rear.
18. Mount the electronics assembly at the right side. I used only 2 screws in the top part.
19. Put the wifi antennes through the 75 mm hole in the rear. Mount them in 2 different directions using double sided tape.
20. Apply kit/glue on top of all wooden parts. Mount and secure the top plate of the BESTÅ base element.
21. Apply weatherstrip at the front sides of all panels and lumber. In the picture you see that I initially forgot one strip.
22. Drill the 75 mm hole for the woofer and the 38 mm hole for the tweeter in panel d.
23. Cut out a hole for the SYMFONISK front panel. This is a difficult and time consuming step: this front panel has to fit tightly in the hole.