Backpack-Sized Power/Stereo Equipment

[Mattycakes802]

Hey All.

I'm a rapper (a good one, I promise), and I'm trying to construct a backpack that will include the following:
2 x Speakers of decent quality (definitely capable of providing decent bass, although I'm obviously not trying to carry around a sub.)
1 x Microphone input (XLR preferably, although anything will do, I have adapters and whatnot)
1 x Aux input (1/8" or 1/4" - really just trying to hook up an iPod)
Some kind of rechargeable battery that will last for -at least- a few hours.

I already have a world-class seamstress who can make anything work in terms of altering the backpack to accommodate these things, and can obviously figure out the speaker portion pretty easily, but I really have no clue where to start in terms of the power supply and a small, portable input/output/mixer type device.

Any thoughts you have would be greatly appreciated. Yes, I understand that this thing is probably going to be heavy as fuck; just need to make sure that it all fits in a backpack (and still leaves room for a camelback, a bottle, and a few pieces of clothing.

Thanks!

[Sham]

I like your thinking. I've done some funky backpack things, but usually start with a stock backpack and modify from there. You might consider some speakers that could be attached to your arms or legs to make you a complete human dance club!

[some seeing eye]

Your vision has come at a golden age of battery tech. You are trying to optimize energy density per unit weight. You aren't concerned with cranking strength. Lifetime charge charge cycles aren't that important. Cost is a factor, but not the most important.

Look at electric bike batteries. Lithium polymer may be what you find. I don't know where you are but hacker spaces and your local burner list is a good source of technical and fabrication collaborators.

Use a class D amplifier that can handle a power supply in the range of your battery sag directly. The more bass you want to produce the more energy from the battery you will draw. You can get speakers almost for free at garage sales etc. The speakers will have less efficiency in a backpack size enclosure, but most speakers in enclosures can produce listenable volumes on less than one audio Watt.

Get a charger for your battery technology and charge it each day at Snow Koan solar. They offer charging as a service, but for some battery technologies, it is a good idea to bring your own matching charge controller.

The combination of quality rapping, visual quality design in your setup, and DIY ethos would be a great contribution to the event.

[Captain Goddammit]

I'd consider this little mixer http://www.bhphotovideo.com/c/product/8 ... Mix_2.html
and a small car stereo amplifier stuffed in a pocket in the backpack.
Those will both be 12 volt DC and you have a zillion options for power, from battery packs using 8 "D" cells to all the high tech lithium stuff.
If you use 8 D cells, you could have two sets of 8 in parallel to up the capacity. I'd even step it up to 10 D cells, those electronics are fine with a few extra volts and you will be running on a slowly decreasing amount anyway.
For speakers I'd look at grabbing a set off a portable boom box. Those are light and efficient and probably can be scrounged up cheap.

And don't forget the sound-sensitive EL wire!!

They don't call me MC Jiggy Joe Diggy Dog for nuthin ya know.

[Elorrum]

portable systems don't have to be large or expensive.
this is an 8 watt system, 12V (8xAA,) The speakers are takeouts from a stereo t.v. . 3.5 mini jack input.


2x15WS, 2x20W, these are all readily available, and pretty small. You can get more watts, but then you'll probably have to bump up to 24V power supply (edit to amend, that yes, Automotive systems are 12V and get loud as well. I'm only speaking to the bare boards I've encountered) and that is getting less portable, but in a backpack, it depends what you want to carry. Small full range speakers can pack a big punch, and you can even do a subwoofer with a passive crossover. TANG band makes small subs, 5 inches and smaller. For 12V, 8 D cells would last a very long time for 15 watts per channel, maybe 20 hours or more.
the board fits in a gift card tin, though I'm working on getting the board and batteries in the same container, and attached to the hat. Right now, that part is on a string around my neck. It's kind of heavy, so it is a work in progress. My feeling is also that lights are not optional.
For this size of system, it doesn't have to be stereo even. Kemo is a manufacturer of small mono amplifiers that are well enclosed, which might be nice for the playa


Beware: these types of projects will fill your house with parts in no time at all. since you'll want to try a lot of things out, and deals on closeout speakers, take outs, etc. are very compelling.

[nixiebunny]

I designed my own 15W/chan Class D amplifier circuit board for my bike stereo. It runs on a 12V or 16V Lithium pack and even produces USB power to charge a music player.

http://www.cathodecorner.com/bikeboombo ... index.html

For a mixer, any of the little DJ mixers could be modified to run directly from battery power, if you hooked up with an engineer sort. Some are more easier to convert than others.

[BBadger]

Buy or build one of those cheap "Class T" amplifiers you can find everywhere on eBay or even Amazon. They're 10W/channel, and the Tripath TA2020 chip they use was considered one of the chips that "shook the world" according to an IEEE publication.

They have decent sound/power and are pretty cheap. You don't need to make the mods the guy above did for something on the playa, so you could essentially just power up the amp directly and use its output. A complete amp is only like $20 on Amazon.com.

You will need to provide 12VDC of power to the amp to run it. You can buy those 12V NiMH battery packs for it if you can't find LiPo variants, and see how many you need to pack along for a day trip.

[LowePro]

Coincidentally, I'm also working on a portable sound system (for a bike trailer) and I've found a lot of good info here:

http://www.instructables.com/id/Battery ... d-Systems/

Esp the tips on efficiency, weight, sound volume, battery types, etc.

[skidude]

Check out this pack I built. Light enough to ski with.

[maladroit]

It wouldn't be a bad idea to make some kind of subwoofer, actually. Try to find a very small woofer and attempt to build something like the Bazooka tube subs on a smaller scale. What this does is lets you build up one enclosure carefully, which will give you richer sound...and then your midrange/tweeters it won't matter as much. Otherwise you're looking at building some larger enclosures to get good sound out of midrange speakers, roughly the size of bookshelf speaker cabinets. A subwoofer tube is more easily mounted on your backpack, firing downwards or sideways.

[melodiousdirge]

Coincidentally, I'm also working on a portable sound system (for a bike trailer) and I've found a lot of good info here:

http://www.instructables.com/id/Battery ... d-Systems/

Esp the tips on efficiency, weight, sound volume, battery types, etc.

^^ I second that opinion. I have that instructable saved in my reference list - lots of great info including where to buy parts, incl exact model numbers, but also enough info to substitute your own parts.