Lithium Battery powered Bluetooth 2.1 Speakers!
I need a badass portable sound system that is fully transportable and runs on batteries. I checked out original harman/kardon go+play, the bass was definitely amazing, but it consumes 8x mad D batteries and has $300 pricetag. So I look at cheaper alternatives that runs on bluetooth. Can I say i'm not impressed with anything.
I decided to build it myself. What I want is a speaker with subwoofer, a rechargeable lithium battery that doesn't break the bank and wireless solution to make it easier for outdoor use. I would also like them to be integrated so I can easily transport them.
What you need:
[Pic 2-5] - 2.1 Speakers that runs on 12V DC (e.g. Creative Inspire 2400 / Edifier Aurora / MP300)
*** i have not tried using speakers that accept 12V AC, but it should work too.
[Pic 6] - Stereo Bluetooth receiver with 3.5mm jack (or iPod for wired connection)
[Pic 7] - 12V DC Rechargeable Lithium Battery (3800mah variant cost ~$20 on ebay)
Optional [Pic 8-9] - IKEA TROFAST storage box (23cm height) for Creative Inspire 2400)
Optional [Pic 10] - Edifier Aurora / MP300 official carrying case
Optional [Pic 11] - Subwoofer port diffuser using paper roll and straws
Optional [Pic 12] - Subwoofer port extension using stickers / paper
Optional [Pic 13] - 8ohm sub for better battery life
Optional [Pic 14] - foobar2000 Equalizer
Optional [Pic 15-17] - Bigger subwoofer
Put it together:
This part is self-explanatory, you just need to connect the battery to power the speakers and MP3 players to supply the music into the speakers. Think of it this way:
[12V Battery] ========> [2.1 Speakers] <------------ [MP3 / Bluetooth player]
Typically you can use any 2.1 Speakers which accept 12V DC under 2A load. The Creative Inspire 2400 adapter was rated at 1.5A while the Edifier Aurora was at 1.65A. So obviously the latter have worse battery life. Do note that you may need to quickly switch on the battery 2x for some speakers because it draws large current at first second of startup (see video).
Now, to make the speakers truly portable I have to put the speaker inside a storage box. I found one IKEA TROFAST plastic box that fits the Creative 2400. The subwoofer and satellites fits perfectly inside this box and it doesn't wobble when I transport it around. What's better is that I can actually lay the box horizontally or vertically.
For the Edifier Aurora (MP300), you can always use its official carrying case. The compartment in the center can fit the rechargeable lithium battery. Just flip the subwoofer and you can connect all the necessary cable to fire it up.
There is one problem with the Edifier MP300 / Aurora. The subwoofer port opening causing bloated midbass, making it sounds like a cheap subwoofer. To cure this, I added a 'papertube' to straighten the port. The length of the papertube must not be too long otherwise the bass will disappear.
Creative 2400 isn't perfect either. It has lots of port noise, therefore I decided to add port diffuser to minimize the noise. Visit this instructables to learn how it is made using household materials.
I replaced the Inspire 2400 subwoofer driver too. Originally it was a 5.25" cone from CSW with 20W/4ohm rating. Now it is 6.5" cone from Edifier M3300 with 25W/8ohm rating. Wooden cabinet has to be sawn off to accommodate the new cone size. The higher ohm rating translates to lower current drawn and therefore I gain significant amount of battery life. What about the bass itself? I figure 10W is enough for bathroom and beside, the larger cone size moves more air so I didn't lose too much bass in the end.
Lastly, I used SH-1 Equalizer to add some lower bass and compensate bass reflections in the bathroom. The preset I used are different from the picture. Visit this instructables to learn how to use foobar2000 to add more bass to your speakers.
Update September 2012:
I mod the Inspire 2400 further by using a bigger subwoofer from Cambridge Soundworks Megaworks 550 model that I have. The amp recently quit working and I decided not to spend anymore effort or dime to fix it. So I removed the backplate, created my own version that fits Inspire 2400 backplate perfectly using some piece of wood. The subwoofer used here is 8" 150W Dual Voice Coil (DVC) subwoofer at 8ohm each. So I paralleled them to achieve 4 ohm impedance.
To my surprise the TDA8510J inside the 2400 can drive the subwoofer pretty well, despite the fact that it produce less than 10% of watt of the original Megaworks amp. Obviously I have to set the bass knob at the lowest level so it doesn't distort and clip at maximum volume, yet I still hear more bass compared to its original 5" subwoofer at max bass level. Now i have a bad-ass 2.1 speakers which can still run on 12V battery.
I am pretty happy with the result for both speakers. Check out these videos:
Creative Inspire 2400
Edifier MP300 (Aurora)