In the search of building the best 360 degree bluetooth speaker i came across the radialstrahler. The company MBL made a nice speaker using the design principle. I wanted to make a prototype to see how well it works.
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Step 1: Ideas
First i had to know how i can replicate it the best. MBL has uploaded a video on youtube which gives a lot of information about how they did it. To close the gaps between the sheets of the globe they use some kind of w-rubber strip. I couldn't find something similar to use, so i had to do it with the materials i had. I used a JBL CS-4 as donor and was able to make a nice mockup.
Step 2: Finished Prototype
First try i had a lot of wobble during a bass note as you can hear in the video:
To fix it i added a bipolar capacitor to filter the lower notes away and stiffend the sheets. It already sounded a lot better but the efficiency of the speaker is still horrible. Feeding a signal at the same amount of amplification to another speaker sounds a lot louder. Maybe adding that unique w-rubber strip helps but i decided anyway this kind of speaker wouldn't end up in the 360 degree bluetooth speaker. This is how it sounded at the last moment: