Passive iPhone amp

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Project by rockmolsen posted 07-26-2015 10:42 PM 4410 views 21 times favorited 8 comments Add to Favorites Watch

My version of the Koostik mini amp. I used two different woods which made it easier to create the channel for the sound. Made from cherry and walnut 4” W x 5” L x 1 3/8” T. I drilled the speaker hole on the drill press with a 2 1/8” forstner bit then finished it off using a CMT bowl & tray bit in a plunge router. Each of the holes are eased over with a 1/8” round-over bit. This one was for iPhone 4 or 5 (they are the same width 2.31”) – I’ll make one for the 6 next by making the recess for the phone a bit wider (2.64’). The slot width for the phone is 1/2” – accommodates all phones and lets it lean back a bit.

-- Rick --------The measure of who we are is what we do with what we have.

8 comments so far

View observer100's profile


421 posts in 1375 days

#1 posted 07-27-2015 02:57 AM

Simple, functional, beautiful … I really like it!

View verntoolboxjunkie's profile


5 posts in 1325 days

#2 posted 07-27-2015 04:27 AM

That’s awesome! Looks much better than putting the phone in a bowl. Nice project

View kmerkle's profile


33 posts in 2599 days

#3 posted 07-27-2015 01:27 PM

I like the Jackyl>Chainsaw>Woodworking connection.

-- Every project is perfect until it's started.

View hhhopks's profile


654 posts in 2642 days

#4 posted 07-27-2015 03:42 PM

I like how yours lean back a bit.
I assume that it sounds great. Right?

Thanks for sharing.

I am thinking of building some as Xmas gifts (for iphone).
The slot length is dependent on the model.
I am hoping that I can build for the 6 and used plug (s) to fill (shorten) the slot for the 4 & 5?
Do you think that is possible?

-- I'll be a woodworker when I grow up. HHHOPKS

View Cajunrotor's profile


35 posts in 2592 days

#5 posted 07-27-2015 03:42 PM

That’s pretty neat. How’s the sound? I’m not familiar with the Koostik amp. Does this really act as an amplifier? I’m thinking that would be pretty cool if it did.

-- Earl

View gbrown4's profile


116 posts in 2958 days

#6 posted 07-27-2015 05:03 PM

Looks great. I just finished making my version. I used English Oak and Zebra wood. I have a I phone 6 and it works really good. I also made one with two speaker holes. I have a CarveWright CNC which makes it easy to carve the bowls and grooves.

-- Greg, Concordia, Mo

View rockmolsen's profile


278 posts in 1837 days

#7 posted 07-27-2015 10:55 PM

Thanks for all comments. I will try to address everyone’s questions in this post. I downloaded a decibel meter app for another phone and it did increase volume by about 15db. I have toyed around with the idea of a one size fits all model and actually did create one. I will post a picture later. Basically there are 2 channels. Stand it up for iPhone 4 or 5 and lay on side for 6. I learned in making these there is only one speaker port on the bottom right, the other is a microphone. All the phone dimensions are available on the web. Someone that’s in to music told me that if I were to create a round channel as opposed to square one it would sound better?

I do not have a CNC but could see how that would make it easier! Doing it on the router table is not too difficult. I made a homemade fence with adjustable stops just for this purpose to route the slot for the phone.

I purposely made the slot deeper than needed so it would lean back. The problem is accommodating some of the protective cases people have.

Thanks for looking

-- Rick --------The measure of who we are is what we do with what we have.

View rockmolsen's profile


278 posts in 1837 days

#8 posted 07-27-2015 10:56 PM

Greg yours look great also – mix of woods is nice

-- Rick --------The measure of who we are is what we do with what we have.

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