Help, 12V Boombox Project

[krishanparmar123]

Hey guys, I don't know if this is the right category for my question but if it isnt please move it,

Everyday on my way to school I like to listen to my music out loud with my friends, I used to do it with my phone but it ends up hard to hear especially with traffic and such, I made a pair of logitech ls11 speakers portable by powering them off batteries and putting them in a cardboard box, They were alright volume(About as loud as my phone) and had a bit more quality than my phone, But they ran out of batteries within an hour of use and that was getting inefficient and expensive.

So i've decided I want to undertake a project where i'm going to use a 12v sealed lead acid battery and use it to power some speakers and a sub.

So heres what I need.

*Speaker, Preferably a full range car speaker of some sort
*Subwoofer, Needs to provide good bass at loud volumes
*LOUD, Most important bit, Needs to be quite loud that can be heard easily over traffice with good quality and bass
*Portable, Needs to last for atleast 2-3 hours a day and be light.
* Size, Needs to fit in my schoolbag with a bit of room to spare.
*Rechargeble
*Enclosure for all the speakers

This is my schoolbag, It's a Nike one its not too small but its not very big eitherhttp://sportitemsstore.com/product/nike-backpack-bag-sand-blue-athletic-school-gym-travel-laptop-bags-ba4378-414/

I can build my own enclosure.

So does anyone have any tips or anything?
I was thinking 4 inch car speakers and a 6 inch sub?
It needs to be around $100-120
And available in Australia

Cheers

[LogicprObe]

Lead acid gel cells are expensive and heavy.

You want to go lithium.

[krishanparmar123]

What do you mean by lithium?, Do you mean like the normal brand batteries you see in the shops?, Because buying them gets really expensive and they drain too fast. Lead Acid battteries last longer and are easily rechargeble, I was thinking something like this, Not even heavy, Under 3kg? http://www.jaycar.com.au/productView.asp?ID=SB2486

[pete_mac]

How about:

 

http://www.ebay.com.au/itm/Sliver-LP-2020A-Lepai-Tripath-Class-T-Hi-Fi-Audio-Car-Amplifier-12V-DC-adaptor-/230969537719?pt=AU_Car_Parts_Accessories&hash=item35c6db74b7&_uhb=1

 

A pair of 6" or 6"x9" car drivers eg.

 

http://www.ebay.com.au/itm/Pioneer-6X9-Speaker-/231076939494?pt=AU_Car_Parts_Accessories&hash=item35cd4246e6&_uhb=1

 

A suitable SLA battery from Jaycar and accompanying charger.

 

You will never get thundering bass from a setup like this, and you won't be able to use an amp with sufficient grunt to run a larger subwoofer driver (especially with the size and weight constraints associated with fitting it inside your schoolbag!)

[LogicprObe]

I was talking about something like this ........ http://www.ebay.com.au/itm/NEW-12V-9800mAh-Super-Polymer-Rechargeable-Lithium-ion-Battery-/221103685977

 

But the gel cell is cheaper and has more capacity if you're keen to lug it around.

 

Here's a good little 12 volt amp kit.

 

http://archive.siliconchip.com.au/cms/A_101523/article.html

[Upfront]

Don't worry about a sub mate. A pair of 6x9s or even a pair of 6" coax speakers in a sealed box is the go. Ask around and you will find some cheapies for sale or maybe even free. Those little T-class amps that have been suggested will work a treat and if you use them with the lithium battery pack you should get about 2 hours of use.

[krishanparmar123]

My friend says he's gonna give me some 6 inch car speakers from his dads car since he got new speakers (Theyre from a 2004 VZ Commodore).

He doesen't know specs or anything, Will that amp be able to power them?, Also, Would a head unit be able to be used as an amp because i've got a spare head unit from our old car its a sony xplod cdx-gt570, It outputs 50w per channel and it has four channels?

[Upfront]

6" speakers will be good. Nice work!

The problem with using a head unit is the power it will draw. Also the more power it outputs the more power it has to draw too. You could try it before buying the amp but I recon (without specs it's hard to tell) that you'd probably only get an hour or so. You'd be better off with an amp, speakers and phone/iPod as the source.

I forgot to say before that the bigger you can make the box the better. As large as is still practical.

[pete_mac]

Cool, those car speakers will work just fine. They will most likely be 4 ohms impedance. The head unit that you have should also work fine in this application. They are actually closer to 10-15WRMS per channel (much like that little amp on ebay).The 50W figure is an exaggerated maximum output. The head until will give you the bonus of being able to play a CD full of MP3s for hours of listening

 

One thing to consider is that the head unit is 1.2kg, whereas the little lepai is about 300g. If you can manage to connect something like an iPod or similar MP3 player to the lepai amp, you'll save a fair bit of weight, and every kg makes a big difference when you're carrying this sucker to school and back.

 

Have you considered ebaying the head unit to raise funds to cover the cost of the amp and the hardware to build the speaker and amp enlosure?

[Upfront]

eBay the head unit! Good call! You can buy those little t class amps in basic form (no casework) on eBay for about $9 delivered.

[krishanparmar123]

Thanks guys, ill probably sell the head unit then, 

[Upfront]

I hope your posting pics of this as you build it mate!

[krishanparmar123]

Yeah i will be posting pics when I build it, Is this amp actually 100 watts as it claims?, http://www.ebay.com.au/itm/TDA7498-A1-TL082-100W-100W-Class-D-amplifier-board-YJ-/330921120077?pt=AU_Car_Parts_Accessories&hash=item4d0c6f914d&_uhb=1 It mentions nothing about its RMS.

[pete_mac]

Not sure, but it won't suit a 12V battery and won't suit your chosen speakers. 

 

Don't aim too high... the larger the power output, the lower the battery life.

[pete_mac]

Some battery info:

 

http://www.diyaudio.com/forums/class-d/188588-boombox-battery.html

 

 

boombox examples and info:

 

http://www.diyaudio.com/forums/class-d/215095-another-lepai-ta2020-boombox.html

 

http://www.diyaudio.com/forums/class-d/230409-looking-advice-selecting-amp-12v-supplied-portable-system.html

 

http://www.diyaudio.com/forums/construction-tips/201915-mini-150-ultimate-boom-box-lepai-2020-a.html

 

 

The above threads are only just scratching the surface... there are hundreds, if not thousands, of DIY boombox threads using the Lepai amps or similar out there on the web. 

[krishanparmar123]

Found some Genesis 100w car speakers under my bed and it sounds pretty good right now hooked up to my reciever so i've put it into a piece of wood for the time being and when i get my other speaker i'll get more wood and turn it into a box.

Just wondering will the 20w lepai amp even power the speakers to decent volume?, I was considering getting this Amp as it does 75w RMS and is only 20 bucks more? http://www.ebay.com.au/itm/New-PowerVox-1400-Watt-2-Channel-Car-Amplifier-Silver-/350810289806?pt=AU_Car_Parts_Accessories&hash=item51adec368e&_uhb=1

Just wondering will the 20w lepai amp even power the speakers to decent volume?, I was considering gett

[LogicprObe]

I thought you wanted something light?

Besides.........your battery will power that for about.........oh........5 minutes?

[Upfront]

20w will be heaps mate. You'll be surprised how little power out of your 75w receiver your actually using.

[krishanparmar123]

Hey guys

I picked up a Sealed Lead Acid battery at Jaycar today, Just wondering how I would go about charging it? Do you need a special charger or anything? Can you just hook it up to a wall plug that does 12v?

[LogicprObe]

Hey guys

I picked up a Sealed Lead Acid battery at Jaycar today, Just wondering how I would go about charging it? Do you need a special charger or anything? Can you just hook it up to a wall plug that does 12v?

 

They require a special charger or you will break it.

 

Like this.............. http://www.batterystuff.com/battery-chargers/12-volt/gel-cell/

[pete_mac]

Hey guys

I picked up a Sealed Lead Acid battery at Jaycar today, Just wondering how I would go about charging it? Do you need a special charger or anything? Can you just hook it up to a wall plug that does 12v?

Jaycar have suitable chargers too.

[krishanparmar123]

Would this do the job?

http://www.gumtree.com.au/s-ad/sumner/other-parts-accessories/-arlec-12v-car-battery-charger-/1030997699

[LogicprObe]

It would...............but not as good as the more modern six step chargers.

[krishanparmar123]

Hey guys

I tried to use the battery and stereo and hooked up one tweeter to test with, All was good until I smelt burning and turned it off, then when I looked at the wires the Power Ground and remote wire were all melted and burnt.

After making sure everything was okay I tried to plug it in again but the second I plugged the wiring harness in the stereo, The fuse blew.

What could be the problem here?

[LogicprObe]

What stereo?
I thought you didn't have one yet?

Please post pics of your wiring.