Introduction: Smart Phone Passive Amplifier

About: I'm a single father, and much like most men, I enjoy building things, learning, racing my Mustang. I teach high speed driving and work in the government sector.

My version of a cheap and fun to build Passive Amplifier for your smartphone. There are lots of versions out there, some beautifully done in wood, others done with paper, and various other construction materials. My version uses readily available items from a local hardware store and provides a way to change the tones, and audibility of broadcasting your favorite music, news, or even phone conversations.

The total cost for this project depends on where you obtain your parts, but all of them are "very cheap." This design also allows you to acquire a variety of sounds based on the setup of the project. Total time to build can be a little as just a few minutes, or upwards of an hour plus depending on which version you like.

Since I'm gimped up right now (shattered my ankle into 10 pieces ZipLining), I've been looking for some simple projects to do while not being able to move much. This seemed like an obvious answer. A quick trip to the local Home Depot (they didn't have much for PVC fittings) and I was off and running (or hobbling on crutches as it is).

Almost all cell phones and tablets have their speakers on the rear of the device. Why? Probably to give me something to do while healing. I currently have one of the largest phones made, a Samsung Note II, which has been coined as a Phablet (part phone and part tablet). Like most other cellular devices and tablets the external speaker is on the lower rear portion of the device and when listening to music or watching movies it's very hard to hear at times depending on the environment. I almost always cup my hand around the rear of the phone to hear what's emitting from the rear speaker. To help hear your favorite music, news, movies, conversations, or even alarms in the AM, I've come up with a few different designs

Step 1: Tools and Parts Needed

I only used three tools in this project, a Dremel, Speed Square, and PVC Cutter (and a Sharpie). The Dremel tool of course had a couple of different attachments I used. The parts purchased is a 10 foot piece of 1 inch PVC Class 200, 1" inch 90 degree elbows, 1 inch end caps, 1 1/4" x 1" 90 degree elbow. Parts lists and prices from Home Depot (others are similar).

1" X 10' PVC Class 200 PVC Pipe
1 @ $1.68
1" PVC Pipe

1 1/4" x 1" PVC Elbow
2 @ $1.44 = $2.88
1 1/4" x 1" PVC Elbow

1" PVC Elbow
2 @ $0.65 = $1.30
1" PVC Elbow

1" PVC End Cap
2 @ $0.53 = $1.06
1" End Cap

1" PVC Tee
2 @ $0.86 = $1.72
1" PVC Tee

Total in Parts: $8.64

The total can be greatly reduced by purchasing just the parts that you need, but I wanted to experiment with different setups and configurations.

Step 2: Measure the Phone and Cut the Tubing

My Note II, with case on it, measured 3 3/8" wide and 1/2" deep. To measure the length of PVC Pipe you'll need take the width measurement (3 3/8") and include the depth of both end pieces you'll be using. The 1 1/4" x 1" elbow measured one inch in depth and all of the 1" fittings were 1 1/8" depth of insertion. So, if you are going to use the 1" Tee's on the end of the main tube, it would be 3 3/8" + 1 1/8" x 2 or 5 5/8" total length. You may want to add an additional 1/8" to 1/4" of length so as not to pinch the fittings against the phone, your call...

Once the length of pipe is determined and cut, you can then trace out the initial cutout needed to hold the phone. In my case it is a 3 3/8" x 1/2" slot. In the first photograph I had already cut the slot out and test fit the phone which was nice and tight to hold it in place. In the second photo, with the phone still in place I marked the location of the edge of the viewable screen, not the edge of the glass but the edge of the viewable screen. Mark this location for an additional cut as viewed in the third image. This second cut was to give me access the screen functions that would otherwise be be hidden inside the tube, but still hold the phone securely in place.

Once you are done with this you'll want to cut a few pieces of pipe 2" long for piecing together the system, see the next step.

Step 3: Design the Amplifier

At this point, it's pretty much done and now comes down to the look and sound you are looking for in the Amplifier. In my testing of several different configurations the best one for sound and stability was the simple Tee's attached to the main tube (Photo #1). This setup provided both forward and rearward firing sound giving it a slightly richer tone as it reflected off of the rear wall.

My next favorite was Photo #2. The forward firing tube, and open ended Tee provided a better sound again as you were changing the two methods of delivery.

The remainder are different configurations I came up with playing with the various pieces. Kinda fun to add and remove the pieces and testing the sound you get from each. The setup I really didn't like included the 1 1/4" x 1" Elbow. I just didn't like the sound being emitted from the larger elbows.

Anyway, the volume improvement is actually pretty impressive and my lady actually said, "wow," when I demonstrated the little device to her. Have fun playing with the setup and find what works best for you...

Step 4: Made a Few More...

Just as an update, I've made a few more of these for around the house...

One in the bedroom as a charging stand/alarm amplifier.

One in the bathroom for amplified music play while taking a shower.

One in the garage for working out there on projects.

One in the backyard for music amplification.

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