Over the last year I’ve read a lot of instructables for boomboxes and the like. As I started to make my own, it became clear that most of these are lacking in a few ways:
- Detail about the wiring
- Building something reasonably useful
- Reasoning regarding parts choices
- Level of DIYness
- Availability of Parts Chosen
- Pretending that you can just hook up a Bluetooth receiver to an amp, run them off the same battery, and that this will not produce an ungodly noise.
This instructable, The Speakerboxxx – Hi-Fi Boombox From Scratch, is not perfect either. But I would recommend it for a couple things it does well.
- Loud, but reasonable, design.
- 2-Way is cool, allows a DIYer dig in a bit but not too complex. I’ve read a fair bit about crossovers now, and built overnight sensations, but not actually figured out how to cross two drivers, done it, and lived with the consequences.
- Uses woofers available cheaply from Parts Express at <$5 each. They are buyouts but have been available for years. I found his guide while looking for builds using this woofer.
- Uses other reasonably sourced parts and lists them all (battery, means of charging, and magnets for attaching grill plate are exceptions).
- Gives a reasonable suggestion for eradicating Bluetooth noise. A ground-loop isolator.
- Buys an amp made by Sure. They are a bit pricier, but with all the samples we have been messing around with, the Sure ones are always louder and don’t push into high-distortion territory as they get loud.
Of course, I’ve had problems with using loop isolators to limit noise, and would recommend to anyone starting out to think about buying an integrated amp+Bluetooth. Problem: 1) None yet available from Sure. 2) BT amps tend to have weird buttons and layouts. Still, that’s what I would buy today. Luckily, if you wait a bit longer, this should solve most of everyone’s problems for a measly $40.
His choice of tweeter, a mid-priced Dayton at $10 each, seems out of whack with the penny-pinching design, but these two drivers look to be well-matched, at least as far as you can tell since there isn’t an actual graph available for the woofer. They extend far into each others range and have the same sensitivity, limiting the work needed to be done by the crossover. Of course I haven’t designed a 2-way before, but I’m a bit scared of ending up with awkwardly crossed drivers.
As for the battery, there are a couple ways to go. If you want loud at this level, you need at least 12 volts. There are CCTV batteries that fit the bill, but most are designed to be removed to be charged. They have only one port that doubles for charging and powering, not ideal for a boombox. There is a line however that comes in blue. They have two leads, one for charging and one for powering your boombox, and a power switch.
Here’s a (supposedly) 8000Ah version on eBay. I wouldn’t trust these ratings to be accurate, but I’ve bought two 6800mAh versions (one from eBay and one from dx.com) and they both work great and power a boombox for many hours. They tend to have ranges from 1800mAh (~$10) to 50,000mAh (~$50). Ordering batteries these days seems to be uncertain anyway as the safety issues with transporting lithium-ion and polymer are better recognized. So expect to wait if you’re ordering from overseas.
One bit of advice and a quirk to know about with these batteries. Get the one with the correct charger. You may have a 12 volt adapter, but a charger is a bit different, and really useful. These tend to come with chargers with a red and green led (and no instructions).
- Red – there is power somewhere. Maybe in the plug, maybe in the battery.
- Green – charging.
- The switch on the battery must be on for the battery to charge. This also means that whatever you hook the battery up to will be powered when the battery is charging.
The other option would be to build your own, a topic for another post, and another aspect of DIY boomboxes it seems hard to find enough information about.
I’m getting started right away. I ordered the drivers, resistors and inductors in the guide from PE this morning. I can use the capacitors I’ve got around for the rest of the crossovers. Not sure about the magnetic grill. Seems like a good idea, but the magnets he uses are too expensive. Here are some cheap ones on eBay with holes for mounting. I don’t really need another boombox design since I’ve got my Sprite, but it will be interesting to compare the two.
