I made a thing! (Bluetooth speaker modeled from scratch)
I made a thing! (Bluetooth speaker modeled from scratch)
No banana for scale, but let's say that it's not too big and not too small. The dimensions are 295mm tall, 270mm wide, and 240mm deep. If I had to do it again, I would be tempted to go a bit wider and touch less deep. It's probably better to be large in one of these dimensions as opposed to both of them.
Here's the top. It has a jack for charging, a connector to program the DSP, a switch to turn it on and off, and a battery gauge.
The speaker also has a built in handle that's way chunkier than it appears, but is still particle.
The big BOM pieces are a Dayton Audio LBB-5Sv2 for the BMS (battery management system), a Dayton Audio KABD-250 2 x 50W for DPS, amplification, and Bluetooth, a Peerless by Tymphany BC25SC08 tweeter, and an Italian-but-made-in-India woofer (a Coral PRF 165).
The print itself is three pieces: the bottom bit (black), the middle bit (white, blue, and white again thanks to not having enough white left to do it all in white), and the black top. Here's a CAD view that more clearly shows the three pieces:
the three pieces are held together with heat-sets and m3 bolts. There's also a tong and groove like joint to help the enclosure leak less air. I haven't noticed any evidence of air leaks while listening.
The amplifier and battery board mount to the bottom like so:
The middle was printed with some supports for the driver overhangs, but the ports and everything else were designed to print in place without supports.
This is certainly not meant to be audiophile build, but it's surprisingly decent. This isn't my first blue-tooth speaker, or even my first printed loudspeaker enclosure, but it is the first that was somewhat intentionally designed to have OK bass response while also being reasonably compact.
It measures fairly well. Frequency response, along with harmonic distortion, is pretty good. There's zero windowing or smoothing on this plot. I suspect the distortion spikes at 1 kHz, 2 kHz, etc are induced by the Bluetooth stack the board is running since they've shown up in multiple different enclosures and with multiple different drivers.
There's no nasty ringing, caused by either the drivers or the enclosure, so life is pretty good:
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If you do design another one, here's an interesting technique I saw on a random YouTube video:
Make an enclosure that fits together so that the walls have a cavity between them you can fill with a combination of plaster of Paris and pvc glue.
This, combined with separate chambers for tweeters/woofers/subs/etc and a little thought for how the sound exits the enclosure, and you've got a top tier miniature sound system for a fraction of the cost. Although it will be a little bulkier, a little heavier, and takes more time to design, if you want to take another step up from what looks to me like a pretty good first one. Honestly given the 3d printed enclosure I expected all kinds of distortions and noise, but you clearly did quite well. So please don't for a second think I'm trying to say "uhh this way is better" it's just a different way, and one that could be better or worse for many many reasons.
I've seen that approach taken to make the enclosure more "dead", but at these power levels it doesn't really matter a lot. The walls are 1.8mm thick with 30% infill. The top and bottom are PETG and the middle section is ASA. These materials are more ductile than say PLA, so they're inherently slightly deader.
You're absolutely correct that the approach you suggested would result in a slightly better outcome for a bit more weight to lug around and a little more design effort. It just didn't seem worth it to me for this portable and fairly low power application.
Fair enough, given the small dimensions I figured lightweight and easy to repair/replace is the biggest feature you're going for.
I considered adding in a "for if you want to take a step up" to it, but that sounded to me like I was trying to say yours is somehow lesser, which is definitely not the case.
Too bad videos can't give a good idea of sound quality, because I'd love to hear it. Based on the specs I can see, this thing should be a nice little powerhouse in it's own right!
It would totally be a step up, the question is which step ups are worth it given the BOM components and their cost (around $200 for all the electronics and drivers excluding plastic). At the end of the day it's a $20 tweeter and a $45 (used) car door woofer connected to a fairly cheap class D amp using Bluetooth. It has a slight turn off pop (no turn on pop though), it hisses some at idle, you can hear the noise floor decrease (eg more noise) when a Bluetooth device pairs, Bluetooth itself isn't a super awesome media for audio (it is a lot better than it used to be, but your actual quality will depend a lot on device to device configurations), etc etc.
I'm not sure what I would prioritize first for the next step up in SQ, but I don't think it would be the enclosure itself.