Instructables
Picture of Portable Retro Hi-Fi Speaker
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NOTICE:
The electronics for this project are now available as a kit from Jameco electronics!  Includes a blank PCB and all components/connectors required to build this project. 

DISCLAIMER:  Batteries can be dangerous.  They can deliver high current if shorted out and start fires.  If they are improperly charged it is possible they can explode.  Please do not attempt anything that you are not familiar with and do not feel safe doing, and double-check your work.  I am not responsible for any damage or injury due to misuse of these instructions.


Portable audio is a pain.  Its either a huge boombox that eats D batteries like M&Ms, a bad-sounding iPod dock, or a virtually silent mini speaker set.  None of these will do for a true music lover.  Those who are so inclined and adequately skilled can build one that meets their exacting demands with relative ease.  Now you'll be all set for a trip to the beach or camping. 

A couple years ago while building an amplifier project I accidentally burned out the main driver from a set of Minimus 7 bookshelf speakers.  Radioshack has sold this pair of speakers in various forms for over 30 years, and they are well known for their great sound and low price.  I was quite bummed out that I was left with only one, collecting dust in my storage room, unlikely to ever be of use to me as a Hi-Fi speaker again. 

Then I was inspired to turn it into a portable Hi-fi speaker by installing a rechargeable battery, charger circuit and amplifier.  I had most of the parts needed lying around and managed to put the device together for only $15 additional costs.  A thrifty shopper could probably do the project for around $60.  Great value indeed!

In this guide, I will show you how I converted this speaker into a battery powered portable mini Hi-Fi system.  It works great!
 
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JKPieGuy3 months ago

(I've tried submitting this question two other times, but for some reason the "Back-Space" button kept on turning the page back, thus loosing what I had wrote.)

Two questions though:

First, if batteries are usually charged about 2 volts above the battery rating, which in this case would 14V for a 12V battery, then why is 18v needed from the power supply?

Second, is it important to use a laptop charger, or can an AC-DC wall adapter with the same rating work? (Because as far as I know, a laptop power brick is just a cleaner supply of DC.)

Please respond back when you have the chance, and I'll really appreciate it. Thanks.

Also, another thing. You had said if we had any suggestions to leave them in the comments. Well I was thinking if you were to add some "Speaker Grill Cloth Fabric" to the front, it help keep the dust out, and prevent things from puncturing the speaker themselves. Plus it would look very nice if you were to use some vintage looking speaker fabric.

mattthegamer463 (author)  JKPieGuy3 months ago

Hi there, the reason for the 18V supply is so that there is some overhead for the charging circuit, since it uses a linear regulator for a constant current source. The 18V also gives the amp a little more overhead and volume capability when plugged in. The laptop supply is just because you can't beat laptop supplies for voltage and current capabilities, for the price. They can also be found cheaply or for free from a dead laptop. The clean voltage is also nice but any supply should do. I removed the speaker cover because it looks way cooler, and it isn't so obvious that its a speaker box when its on there so it isn't as good for pictures. I lost the dust covers a long time ago for this one anyway. Dust covers really doesn't do muc to prevent punctures but does help against UV damage from the sun.

Thanks for returning my question so quickly, I really appreciate it!

Now that you explained why 18V is needed, it makes allot more sence. So basically what you're saying is: Instead of draining the battery while it's charging, the excess voltage powers the amp letting the battery charge steadily. You also have a very good point about the laptop chargers. You can find them quite easily and cheaply also. I also have to agree, it does look cooler seeing the actual speaker instead of a bland black dust cover.

I do plan on building one of these over the summer, but I can't seem to find any good Bookshelf Speakers lying around (and I don't really want to buy any from for say "Best Buy", cause for the price they charge, you minus well just buy a boombox). Though I do have some old car door mount speakers that my Father got a long time ago and never used. Was thinking of getting some plywood and routing that into a speaker box, though I'd probly make it stereo instead of Mono since I have two speakers. I'll make sure to let you know how it goes once I get around to it. I do want to modify the circuit just a tad, by adding an indicator light which would display Battery at full charge.

Question about that though. In order to get a stereo sound, wouldn't I just build two of the speaker amplifying circuits without the two mixing 1K Resistors at R9 and R10?

mattthegamer463 (author)  JKPieGuy3 months ago

Yes, just remove the resistors and send one channel to each circuit. For the full charge indicator, use a NPN transistor and a LED, and a pair of resistors that put 0.7V on the base of the NPN when 12V is coming from the + of the battery. The LED won't light until the voltage becomes 12V. You could use a trimpot in place of two resistors to make it adjustable trigger.

usMudack19989 months ago
Could you make an instructable on how to incorporate a Radio and Auxiliary device in as well? Built in to the housing that is...
mattthegamer463 (author)  usMudack19989 months ago
Really it wouldn't difficult to do. If you can't imagine how to do it then how will you be able to accomplish it?
ManishS12 months ago
Thanks for sharing! It is superb and so easy to handle...

I would also show you portable electric router..It is so easy to use and easy to handle..

http://www.endicopowertools.com/portable-electric-routers.php

nettro11 year ago
Very cool
gquirino1 year ago
uhmmm what will happen if I failed to build a crossover and instead, directly connecting the tweeter and sub together? if the crossover is really needed can you please teach me how? 'cause im still new on these things and i would like to build this project because im also a music lover and a portable speaker will help me alot..thanks in advanced!! :D
mattthegamer463 (author)  gquirino1 year ago
A simple crossover is very easy to make, it only contains two components.  This tool will help you out http://www.diyaudioandvideo.com/Calculator/XOver/

Without the crossover some speakers can get grumpy about having to try to handle low frequencies (tweeters don't like that) or high frequencies (woofers just plain can't do it) so there's good reason to include one.  Sound quality will suffer without one as well.

dtbingle1 year ago
The kit by jameco with all of the components is either not complete or am I missing something? Unless I completely overlooked something, I don't see the .5 ohm 5w resistor, 1k resistors and has extra 47nf caps in place of the 37 or 39nf caps (can't remember which) in this jameco kit. Am I doing something wrong?
and ,, how it sounds???????
It sounds great!
because is very good men
nilnate5191 year ago
what type of Terminal Block was used for the project, looking on digikey and too many options for me to make a well informed decision
mattthegamer463 (author)  nilnate5191 year ago
Hi, The T-block can be any 0.2" (5.08mm) pitch T-block or connector. Digikey part ED2609-ND or similar.
nilnate5191 year ago
I am wondering what speaker and subwoofer to buy to make this a good project. Are these good speakers Tang Band W4-930SF. What about Subwoofer? Also recomend components that would be easy to get at a Radioshack
mattthegamer463 (author)  nilnate5191 year ago
Maybe these will work for you

http://www.radioshack.com/product/index.jsp?productId=10951399&filterName=Price&numProdsPerPage=60&filterValue=%2410.00+-+%2449.99
Also how do you hook up the subwoofer in the circuit and if I just wanted to buy speakers could I make my own inclosure?
mattthegamer463 (author)  nilnate5191 year ago
You will have to design a crossover circuit to filter low frequencies to the subwoofer and high frequencies to the tweeter. Crossover design is not a simple thing to do so I recommend you just get/buy an old speaker to use. Speaker cabinet design is also a pretty math-heavy thing so I recommend getting/buying a speaker for that reason as well.
What are "VCC" "T Block" and "Wi" also how does the battery circuit connect to the speaker circuit.
mattthegamer463 (author)  nilnate5191 year ago
Vcc is the circuit voltage. T-blocks are screw-down wire terminals. I don't know what Wi is or where you got that from.

The circuit schematic is pretty straightforward. There is a switch that disconnects the battery from the charging circuit and hooks it to the amplifier circuit.
brendan9451 year ago
I think as evidenced by the comments here, this is a great jump off point for anyone looking to build a portable audio system. I have been kicking this idea around for a while unsure where to start. This is exactly the kind of instructable I've been waiting for.
Maybe I'm confused but I read through this a couple of time and viewed the PDF. Where are you buying all of the electronics parts from?

Additionally how did you do the PCB? I actually have quite a bit of "blank" PCB but I'm not sure the best method of transcribing/etching onto them. What do you recommend?
I didn't say where I got my parts since for most people it is up to their preference to get them from a local store, internet, eBay, etc. and people's location determines where they can and can't buy from. Listing sites would be mostly useless. I get my parts from Digikey but almost all these parts are available anywhere that sells electronic components. Even Radioshack should have all this stuff.

I made the PCB using the laser printer and magazine paper iron-on transfer method. Works great and is practically free. Alternatively PCBs can be manufactured in china by internet order for as little as $1 apiece. Here is a guide I loosely follow to do my boards
whizbo2 years ago
I built a slightly larger speaker on the same premise.
http://stories.parts-express.com/stories/2444-en_us/category/Speaker/story/16637/redirect.htm

There are lots of efficient Class T amps out there. That can save you some time. Here's a wonderful review http://www.tnt-audio.com/ampli/tripath_amps_e.html

I went with the The 41HZ AMP-3 and I've been very happy.

Technically mine is portable, but it's not light. Your design looks like a great size. Cool build!!
lil_ricky.jpg
mattthegamer463 (author)  whizbo2 years ago
Thanks, thats pretty great, how long is the battery life at a reasonable volume?

8 hours of great sound, then the base starts to distort a bit and requires the volume to be turned down.
add this
http://www.amazon.com/gp/product/B007R8PVJS/ref=oh_details_o01_s00_i00
cheap and sounds great
i just put this into some earmuffs turned out great
Joe_M2 years ago
I think the amp is a litle like reinventing the wheel. There are some great low cost amps that have a RCA input, volume, tone, and head phone, that would do nicely on that big battery. They are stereo, but I think there are some that can be set to mono, and double the power to one channel.
I love the idea of making your own kick-ass boom box. You could incorporate a cheap mp3 type player, and add any amount of ram of MP3 music, or whatever audio format you like.
mattthegamer463 (author)  Joe_M2 years ago
Yeah definitely. The integrated MP3 player would be great. Deal extreme has some really good looking ones for $10. The amp and battery charge circuit on one board was unnecessary but since I didn't have either as a pre-made or kit type, I just made them myself. Good practice on the PCB making techniques too. Haven't made one that way in over a year.
Elipsit2 years ago
Solid project as per usual. Not sure why there is so much flack about pricing, the main focus of an instructable...is to instruct, which he did quite well.
Trike Lover2 years ago
Interesting project. Your idea of including a rechargeable 12 volt battery is a good one. If I were building it I think I would also make some provision for a cord to connect to an automobile cigarette lighter socket, using a power cord jack with a switch that would disconnect the internal battery and connect the car battery supply. You might also want to include a switch (DPDT, center off?) to give the option of charging the internal battery directly from the cigarette lighter input, bypassing the charging circuit. You would then have the option of internal battery power, external auto battery power, or charging the internal battery.

Another provision that might be useful would be to put in a 7805 regulator alongside the LM317, the output of which would go to a jack where the power cable for an mp3 device could be plugged in (all mine run on 5 VDC at less than 500 mA. Connector choice would be up to the individual; a chassis-mount standard 4-pin USB socket would probably mate with most mp3 player cords. (+5 VDC and Gnd. on pins 1 and 4).

If you wanted to get really "green" on the battery charging side, you might consider purchasing one of the small "battery maintainer" solar panels that put out about 14-15 volts; output power is 1.2 - 1.5 Watts.

I frequently see these on sale for as little as $10. They have built-in car battery-charging circuits, so you could again use a switched cable input jack, with the switch bypassing the internal charging circuit, and connecting the solar panel directly to the battery. If you were having your fun in the sun, one of these would charge the battery without an external power source, and extend your "run time".

If your speaker box was a bit longer, the panel could mount right onto the box. Alternately,, devise a folding stand with a few pieces of stiff wire, or wooden dowels, to align the panel at the best angle for maximum solar capture. Have a couple of clips to hold the panel onto the box side when not in use. These panels work even if placed in the rear window of a car, or on a bicycle carrier rack, so it could continue to charge the internal battery in transit.

Finally, for those who don't want to etch their own boards or build their own amplifier board, single-chip mono amplifier boards with suitable power outputs and input voltage requirements are available on various online auction sites, some for as little as $10. The lazy man's way, yes, but for those with less experience in building circuits, these offer an alternative, and still let the builder do the other parts of the construction.

Just a few thoughts, not meant as a criticism of your very neat and attractive project.
mattthegamer463 (author)  Trike Lover2 years ago
Wow, yes a lot of good points. The lead acid charging circuit would need to be changed, this one requires a 18V input voltage so charging from a car cigarette outlet wouldn't work. Definitely some neat ideas for somebody building a beefed up version of this. Thanks for the big post.
Yes, I looked at your schematic and wasn't entirely sure why you'd gone for the 18 volt charger input. The SLA's will charge directly from a car cigarette lighter socket and don't seem to suffer any ill effects, based on my own experience.
The mini solar panel already has a charge controller built in, so no problem there.
Another option, if you _really_ want 18 volts at your charging circuit input and have only 13.8 VDC available, is to order a voltage "boost" board from EBay. These are essentially an upconverting switching power supply on a board, and will accept a variety of input voltages and give a set output voltage.

Anyhow, I'm trying to shoehorn a guittar amp, mixer, rechargeables, jacks, pots, etc. into a traveller's soap dish, to give a rechargeable portable headphone guitar practice amp. It's a tight fit.

Cheers & good luck.

P.S. I used four of those 1 watt solar panels to "top off" a 20 AH SLA battery, which in turn was running an electric cooler. They did a good job - I only had to resort to the "real" charger once in a while, I was surprised.
mattthegamer463 (author)  Trike Lover2 years ago
When you charge the 12V batteries directly from the cigarette lighter, can they be left indefinitely or do you need to make sure to unplug them after a certain amount of time?

Also, I bought that battery from a local store, brand new, for $15! Don't know why people keep telling me it is worth more than that. If it is, I guess I got a great deal.
Your second point first - Yes, that is a great deal! I did some more checking around this morning and the lowest $ I found for that size of battery (new) was $27. So I sure wish I lived near your store, LOL!

Charging from the cigarette lighter, you can leave them plugged in. The regulator in the alternator will not charge the car battery to more than 13.8 volts, and thus your SLA battery, which is effectively in parallel, will also not exceed the 13.8 volts. As the battery voltage rises to the maximum value, the charging current decreases. There is some extra load on the alternator, but for a battery of this size it's minimal.

When I am manually charging one of these, I periodically check the SLA battery voltage with a meter and disconnect when they're at or above 13.6 volts. The one thing you don't want to do is have it in the circuit when you're starting the car - hard on the smaller battery.

I have a pair of 20 AH SLA batteries in the trunk of my car, to run ham radio equipment independently from the car battery. A simple isolator relay disconnects these from the car battery when the engine is not running. So, if the radios run the trunk batteries down, my car battery is unaffected. There are also solid-state battery isolators available, but I've found the relay works for my needs. I do have a remote voltmeter near the dash and the radio and antenna controls which shows the trunk battery voltage.

Been digging around my tickle trunk and found an ex-stereo speaker in a good box about the same size as yours, so I'm going to give this a try. Cheers.
mattthegamer463 (author)  Trike Lover2 years ago
Sounds like a good idea. I wanted to take good care of this battery ($15 is still a good chunk of money) and want it to last a long time, and read that a regulated charging current, and not greatly exceeding 12V will keep the battery optimal.

Good luck with your project.
A short P.S. - the SLA battery in your photo costs, new, considerably more than $15, even from wholesalers or when on sale. Even if all other parts were on hand, the battery is quite costly if purchased new. Any suggestions as to an inexpensive source for cells of this size? Just curious.
sshim12 years ago
this is great but a video along with this would help better explain
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