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I'd like to mount a small 8W speaker inside a 3D printed plastic casing, and I'm looking into possible mounting options. However, I see quite a few problems. Speaker could shake out from it's position, stress the PCB, stress the wires that connect it to amplifier, muffle the sound, etc.

As I see there are 3 types of small speaker shapes:

  • Small non-round ones that are usually found in smartphones (like this one), which seems to have a sticky tape - but I'm concerned about the glue wearing out due to vibration. I guess they are pressed into plastic by some hard-foam behind them (which also prevents PCB from receiving vibrations from speaker).
  • Bigger round ones with flat design (like this one). I'm not sure how to expose plastic membrane, and at the same time protect it from piercing. Looks like they should be fitted inside a recess in plastic, but I'm not sure how to hold them on their back side.
  • PCB mounted speakers (like this one). I like the supposed easy way to mount them, but I'm very concerned about shaking the PCB all the time, and harmonic distortions from PCB oscillating, as well as the inability to mount them directly on casing (which I guess would reduce the sound level and also distort it)

What is the best way to mount a speaker inside plastic case? I'd also be grateful for any hints and especially shared experience regarding durability.

cactusresistance
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  • Are you looking to attach it *permanently*? – Andrew Morton Dec 28 '21 at 17:46
  • Yes, I'd like to permanently place it in box, and if possible make small batch of 10+ such devices and give them to a few friends (so it should be somewhat sturdy). – cactusresistance Dec 28 '21 at 17:47
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    There is no one good answer. Go to the closest Goodwill store, or somewhere else that you can get electronics junk for cheap. Buy a few things that are at the level of sophistication you're interested in, take them apart, and look at how the speakers are mounted. Remember that the first rule of engineering is that if you can shamelessly copy a solution from someone else and it works perfectly well, you should do exactly that, and save your brain power for the unsolved problems. – TimWescott Dec 28 '21 at 18:00
  • doesn't the speaker have mounting holes? ... do you realize that you are asking a question about an unknown component? ... please add a picture of the speaker – jsotola Dec 28 '21 at 18:17
  • @TimWescott I'm trying to make a informed decision based on solid engineering practices, and copying cheap gadgets might show 'a way' how it's done in China. I'm trying to prototype a device that users will love, not a device that 'somewhat' works. Please don't get me wrong, I do appreciate your feedback and it is a good advice in general. – cactusresistance Dec 28 '21 at 18:22
  • @jsotola I've linked to 3 types of speakers (linked site also has the docs for them). – cactusresistance Dec 28 '21 at 18:25
  • I specifically suggested Goodwill because you can choose to get funky old used stuff that used to be high quality. In general, make sure that the speakers are mounted firmly and that neither they nor the case can rattle. Beyond that you're getting into details of acoustic design that require a course of study (and the disassembly of lots of high-class electronics) to master. – TimWescott Dec 28 '21 at 18:29
  • What's your application? A buzzer or warning squeal requires different treatment than voice and/or music. Mechanical resonance is to be encouraged for the former, suppressed for the latter. – glen_geek Dec 28 '21 at 18:39
  • @cactusresistance look at CR2032 cell holders ... https://duckduckgo.com/?q=cr2032+holder&iax=images&ia=images – jsotola Dec 28 '21 at 19:30
  • You're specifying a fairly big 8W speaker while talking about mounting little speakers in phones and the like. Look inside old radios or cassette recorders. The speaker will be held in with 3 metal brackets screwed to the case. – Simon B Dec 29 '21 at 11:13
  • You wrote 8W speaker, but did you mean an 8 ohm speaker? – Andrew Morton Dec 29 '21 at 20:49

2 Answers2

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Bigger is better with a solid baffle. Otherwise the high self-resonant cone frequency will sound very 'monotone' at 600 Hz.

Attachment is easy using any Polyurethane adhesives (sub-floor type in a tube) such as LePages PLxxxx or whatever. Allow 1 day to cure 50% and 3 days to fully cure with Rock hard 60 or depending on model. (Its also good for getting rid of subfloor squeaks) Good for wires and large caps. Anything that can move can be secured with a small dab or thin seam to nearest solid brace. It can be applied with disposable plastic knife or equiv. from the tube gun. (I use it for everything, that I want permanently secured:...kitchen slides on heavy drawers full of canned goods, shelving back edges) It can be drilled so it is not brittle like epoxy and will not resonate. Much stronger than PVC or ABS.

In Electronics industry , they use white PU, PolyUrethane with a lower shore hardness perhaps with faster UV cure. You will see that on all power supplies.

Tony Stewart EE75
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Tony Stewart has given you brilliant advice regarding how to use adhesive to mount the speaker.

You can incorporate a grille in your 3D print design to allow the sound to project while protecting the speaker cone. If you're worried about even smaller objects penetrating, you'll need a second, offset grille behind the first, but that's trickier to print.

Whatever volume the case provides, it's your "baffle". The back of the speaker has to project into this volume. If you're picky about sound, your speaker may sound better if you fill the internal volume with some soft polyfoam.

Here's an example of a 3D printed design I did with a small speaker, which was adhesive mounted to the case front. I've shown an internal view where you can see the circular recess for the speaker. This design was for a first responder spkr/mic unit and had to be loud! Worked great. enter image description here

enter image description here

Mark Leavitt
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