These smartphone passive amps are probably more of a novelty than actually are useful. I have designed a few of these and I keep trying to get more volume. This is the best I have designed so far. I have not measured the volume increase but I would guess it is about a 50% to 75% increase.
It does also have another benefit. It seems to increase the fullness of the music. Maybe more bass?
I made this prototype out of Baltic birch plywood but you can also use a nice hardwood.
I added a leather seal over the opening to help keep the sound in the channel.
After I glued up the tube I sanded an angle so the cone would be angled up. It just looks better.
$12 per sheet of 12 coins plus $3.50 shipping
Inlay with a 1" Forstner Bit.
The perfect way to sign your work.
Email Newsletter Readers: Remember that the Newsletter is just a copy of the daily blog post. To see the post in it's proper formatting click this link. If you ever misplace a pattern or any item you see here you can always find it on the blog. Everything stays on the blog forever.