Universal Phone Speaker (Passive Horn Speaker)

thingiverse

# Universal Passive Horn Speaker for Smartphones Quite Easy to make ## Design Horn speakers are known to increase the perceived volume of a speaker, even without adding an electronic amplifier.They effectively bundle the sound waves and increase acoustic pressure. Originally I wanted to design an exponential horn. However, I also wanted it to fit on common printers and I wanted the printing process to be easy enough for most people. After checking some options, I decided to design a linear horn, instead of an exponential. I might try an exponential design in future. I decided to go with a 3 piece design and the glue it together. I added the 3D design as STP files too, so others can use it easily. ### How is it universal ? It is wide enough to carry probably all phones on the market and the width is not physically limited by the design. The slot that holds the phone is 14mm wide, which should be enough for most phones It has an open sound port on the right side but also a "pre-cut" sound port on the left (see pictures). As long as you have USB-C or Lightning and the connector is in the bottom center, you should be able to use it with the power cord connected to the phone. ## Printing The pictures of the "work-in-process" print beds show which sides of the parts should face up. As you can see in the pictures, I could print both side covers in one print on my Prusa i3. If your printer is smaller, you might need to print them separately. Make sure you have a good first layer sticking, when you print the horn or consider using a raft. As you can see, I did not need one. See the print settings section for some other details. ## Assembly First of all check, where your speaker is! On iPhones, the speaker is on the bottom right side. If your phone has the speaker on the bottom left or has speakers bottom left and right, use a sharp cutter (or your favorite tool) to remove the recessed plastic area on the left side of the horns phone holder area. The plastic is only 0.4mm thick there, so it should no be too difficult to cut out. Next, place your phone in the correct place and check, how well the speaker fits the sound ports in the horn. The sound ports are quite big and your phone might not cover all of it. The more "air-tight" the interface area is, the better your horn will perform. It will work as it is and you can proceed without spending time here. However, if you want to get the best out of it, you might want to close part of the sound port(s). I have experimented with 2 layers of insulation tape and I could hear the difference, especially when I removed my phone from the (relatively soft) protective case, it is normally in. Next, make sure the coves fit on the horned you can assemble the 3 parts completely without applying a lot of force. Carefully look, where the cover and the horn touch each other. After this check is completed, put some glue everywhere on one of the covers, where it touches the horn part. Lay the cover flat on the table with the glue facing up in press in the horn part. Then put glue on the other cover and press the second cover on the horn part. Fix it with rubber bands, screw clamps or heavy books and let the glue set. I am either using semi or high viscosity cyan acrylate glue or plastic glue(I really like "Pattex Spezial Modellbau" because it has a nice applicator). ## Expectation Management Of course this little plastic thingy cannot really boost your low frequencies (base) significantly. It increases the total volume though. If we were to build a horn to boost your base, we definitely needed an exponential horn and it needed to be significantly longer. An expo horn with a lower cut-off frequency of 100Hz for a driving speaker with (hypothetical) 20mm^2 membrane would be 5.85 meters long and have a mouth opening of 0.93 m^2 I guess you get the point. If you want to get as much base as possible put the speaker in a corner of your room. The corner will help you to gain the most possible base. -----