Cheap-ish DIY Portable Bluetooth Speaker Questions

[Thijsiez]

Hej there, DIY-enthousiasts and audiophiles alike

I have to preface this thread with the fact that I'm a complete noob at audio-related technology, although I know some jargon. I first posted this on another forum where I have posted before but that specific forum is mostly inhabited by computer guys/software engineers/etc. I quickly realized that my chances of getting a useful answer here are much higher (Yes I know that's not allowed according to rule 14, I didn't think it through that well and can't delete the thread on the other forum as far as I can see, but I edited it, asking the mods to delete it)

So for the project description, I decided to start building a cheap-ish but (hopefully) good portable bluetooth speaker, which I will house in a 3D printed enclosure which I will be designing around the picked hardware in a later stage. This is the hardware I'm currently looking at:

Battery:
6800mAh for DC 12V Super Protable Rechargeable switch Lithium-ion Battery Pack US Plug For Cameras camcorders
I chose this 12V 6800mAh pack so even at louder volumes it should last quite a long time

Boost Converter:
Waterproof DC Boost Converter 12V to 24V DC Converter 3Amp 72W Step Up Voltage Regulator Car Power Supply
I read somewhere that when you provide a higher voltage to your amplifier, it should be able to output a cleaner signal more easily. If 24V turns out to be too much, I thought about using this one instead

Amplifier:
Wireless Bluetooth 4.0 Audio Receiver Digital TDA7492P 50W+50W Amplifier Board Free Shipping
Like I said, I have no experience with audio hardware, but I chose this board as it seemed quite decent and it is very popular, even more so than the comparable boards with the TPA3116D2 IC, which is supposed to be the better chip as far as I could find. For your convenience, here is the datasheet for the TDA7492P, from which I already noticed the 25W+25W rating, and not 50W+50W as advertised, but I can live with that.

Now I have some 4Ohm 20W speakers laying around, which would I would like to reuse in this project, but I wouldn't mind buying new ones if that would greatly increase quality.

I have a few questions regarding my hardware choices:

1. Is it beneficial to run the amplifier on 24V (or 19V) compared to 12V?
2. Would I be better off buying a pair of 8Ohm 20W speakers?
3. Are there things I need to keep in mind while designing and building?

Thanks in advance for everyone who pitches in, much appreciated!!

 

[picowallspeaker]

Boost converter ? It seems rather non-sense since it's battery powered; you can add 2 or 3 cells ( supposing you can do it instead of buying a finished battery pack ) and set for 20 V.
Boost converters consume electricity too - no free lunch !

 

[Thijsiez]

Boost converter ? It seems rather non-sense since it's battery powered; you can add 2 or 3 cells ( supposing you can do it instead of buying a finished battery pack ) and set for 20 V.
Boost converters consume electricity too - no free lunch !

So you're saying that going for the DIY option of soldering together 18650 cells with a battery charging/protection board would actually be a better solution?
In that case, with 5 or 6 cells in series, I'd be looking at 18.5V or 22.2V respectively, which is still within the amplifier's limits.

I found these batteries and charging/protection board, which seemed pretty nice
6 pcs/ Lot New original 18650 lithium-ion Rechargeable battery 3400 mAh 3.7 V for Panasonic NCR18650B batteries Free shipping
5S 5A 18.5V li-ion BMS PCM battery protection board bms pcm without balancing for LicoO2 Limn2O4 li battery

Any input on those?
And questions 2 and 3 still remain

Thanks!

 

[picowallspeaker]

3. Are there things I need to keep in mind while designing and building?

I'd stay focused on the supply part ! Well, during all the designing & building process you should adopt the "professional view" which also means that the final product should make no harm to a third party; this (safety rules ) includes the wiring and the durability of the connections under stress.

Normally, the little BT speakers work below 5 V so that they can be charged with an USB connection. Your project is a bomb in comparison, so be careful.
I guess that if no BMS is used, you'll have to swap battery position once a year ?! Then there's the charger ...
I don't know the matter at all and I'll leave to you the task of studying it

At the very end of the building stage you can focus on the speakers, after having checked that everything works cluelessly.
The impedance and the wattage usually don't tell much; a higher Z ( impedance) brings less stress to the amplifier which distorts less. A lower Z is favoured when low voltage is used, such in these applications, because the sensitivity rises ( if that makes sense )

Ideally, you would have/want an amplifier ( w/ supply ) module that behaves well on any (kind of ) load, so you can swap speakers or speaker systems to find the optimal.

 

[Thijsiez]

Thank you for your input picowallspeaker

I will surely be adopt the professional view, I agree that's the right way to go.
I decided to go with a 6 18650 cells, 3400mAh each, with a 6 cell BMS, probably the safest and most modular way to go, so if something was to go wrong with a cell, I could just swap it.
I'll probably pair it with 2 8 Ohm 20W speakers, with some thick wires for the high powered connections.

Cheers