I’m not an expert in electronics, and I have a project to modify an Apple AirTag to make it fit in a credit card format (85mm x 55mm) while remaining as thin as possible (3.5mm) to put it in my wallet.
I already have the PCB with the shell removed, cables soldered on the power contactors to place the battery next to the PCB, and a temporary cardboard case (until I make a 3D-printed one). Everything works fine!
Now, I need to replace the AirTag speaker. Indeed, I would not like to reuse the integrated coil because:
the operation seems very difficult (the wires are very tiny, I already broke them during disassembly ).
the volume will be lower without the original shell (see the post below), and I find a normal AirTag already too quiet.
I don’t need to save space, there is plenty of room in a credit card format to easily fit the PCB, a battery, and a speaker as long as it is thin.
So I looked up the specs of the AirTag’s audio circuit and came across a great doc by Adam Catley (see the post bellow). It mentions that the audio amplifier is a Maxim MAX98357AEWL whose specs are available here.
I then looked for a speaker that both have a good thickness/decibel ratio and that is compatible with the AirTag. I found a lot of models on Alibaba (strangely, I found almost none on Digikey), and this one seems to check all the boxes:
3.3mm thickness (the AirTag PCB is 3.5mm)
good decibel level compared to the different models I’ve seen (I hope it’s a lot louder than an original AirTag )
specs seem to be compatible with those of the amplifier: Rated / Max. power: 0.7W / 1W ; Impedance: 8Ω
So I would like to get some advice on this choice. Is it really the audio amplifier that determines the choice of the speaker? Do the specs actually match, or am I wrong?
Sorry, I do not remember seeing this post.
The speaker that you referenced above should work but I would expect it to be lower volume as it is 8 ohms vs the 4 ohms that the specs recommend.
You can determine the specs for the voice coil in your original tag by measuring it with an Ohm meter.
Unfortunately, following my message yesterday, I ordered two sets of speakers (speaker 1, speaker 2) without having seen your answer. I hope the fact that they are 8 ohms won’t make the sound too weak. I got one in 1W and the other in 0.5W.
Well, since it’s Aliexpress, delivery was announced for mid-February. But I’ll update this thread when I’ve received and tested the speakers.