There is a scene in Ghost Dog where he has a homemade boombox. It has 2 car speakers, a car amp, and a car stereo/cd head unit. I dont know what kind of power suppy it had. I was just at a BBQ and we wanted to listen to some music from our HD players but we couldnt get good sound out of the cassette adaptor and most boomboxes suck. Maybe for $250 we can build something that sounds good and looks better than a boombox with a cheap HD player through line out to amp to speakers type thing?

I know people here know about car stereo installations and portable gear so maybe you guys can team up and help with this and maybe you can build one on your own for your next barbeque.



Source: What is the cheapest HD player with good battery life, and moddable hard drive capacity?$150

Amp: I think for a boombox 40-60wpc will do the trick. Maybe a class D amp will run cooler and use less power? It should also have 2 sets of outputs (1 for maybe a subwoofer later)50

Speaker drivers: I think speakers with clean treble, nice midrange and good bass are a must. Maybe we can keep them under $60

Power Supply something rechargeable or battery powered is good. Maybe a Sealed Lead Acid Battery?

Let me know all of your suggestions.

For best sound AND to keep it simple you want to use auto sound full range drivers rather than individual midwoofer/crossover/tweeter which would be a major undertaking to get right AND would mostly be power hungry.Do not use full range drivers meant for home use or they will most likely be damged from any direct sunlight or outdoor heat buildup.Car speakers are made the way they are for a reason-environmental extremes.

Once you speaker requirements are nailed down I would look at trying to get around 10 watts clean which in reality is very powerful in this context.The best way to go would be a chip amp and since amp power is related amp supply voltage steal a trick from car amplifiers and use two low watt amp chips in the bridge mode which doubles actual amplifier power output for the same amp voltage and would save on the powering voltage.Look for a design that will work at 5 watts and run of 9-12 volts with low current draw then bridge two and use D-Cells to power the box whic like in a real boom box give the longest amount of battery life though the louder you play it the faster the batteries will drain.Check National Semiconductor for the chip amps.

I think the hard part here will be actual box construction.You want to minimize vibration from the speakers while holding down the weight PLUS it must not be sensitive to the environment (heat,sunlight,slight moisture).No easy task.

the actual player can be anything,even a simple dock for jacking in whatever you have at the time as your source

good luck with the project

Thanks for pointing me in the right direction Rick. Ive never soldered before so Im a real DIY Noob. Im thinking wood/mdf/plywood for the enclosure. It doesnt have to look nice its just for backyards/bedrooms. Im thinking just a wooden box, some sort of cradle for the player and the 2 full range car drivers screwed into a wooden board that would then screw into the box.

How would I connect the chip amps to the power supply and player?

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I personally would stay away from MDf in this case.that stuff weighs a damn ton man !You would need to put wheels on it just to move from point A to point B

If I could make a suggestion go with a dense plywood (as many layers as you can get locally) in 3/8 thickness.but a "half sheet" if your luber yard offers that option,some do in the funiture grade sheets (birch ply) and brace any panels internally that would have a tendency to flex.That is not just the speaker enclosure area but also the control area and any carrying handles.Simple "crap grade" pine is fine for this in say 1/2 inch thickness,3 inch width and cut into lengthwise braces.For an all purpose durable covering look to Tolex.the same stuff used on a guitar amp and not only will it take a flat out beatingf but comes in enough colors to satisfy most artisitic endevours www.tubesandmore.com is a good first source for a lot of the parts.

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Think "integrated amp" and design accordingly.the signal path should look like this :

Opamp gain stage "preamp" to chip amp "power amp" stage.If the opamp is a cmoy type (high output current drive) you would add a DPDT switch to select where the output of this stage goes

Ouput #1-Speakers
Output #2- headphone jack

the player would go to the preamp input which in turn goes to either headphones directly or on to the power amp stage for speaker use.

Other things to consider are a tone control stage,system mute switch and possibly a simple rotary switch input selector and if you add switching phone jacks to the amp output you could even use the preamp and amp with other speakers with the jack switching off the internal speakers and then passing the amp output on to the jack for powering other speakers,maybe higher quality home speakers strictly for "in house" use or even with high efficiency speakers for gatherings and parties.would make the device much more multifunctional instead of locked into a single use.

This puppy looks pretty decent as a starting point.Check the bridge mode connection down at the bottom of the page

http://www.national.com/ds.cgi/LM/LM384.pdf

Hey buddy,

I had the same delima. I was goin gto a music festival and wanted to have some tunes for the campsite. I used a 2- dollar 12V tractor battery and the sonic T amp with a pair of Paradigm Titans. I just plugged in my Karma. It was unreal how much sound came out of the Titans. It was a great time!.

I would highly suggest the T-Amp. I still have this thing hooked up to the battery and I've got about 100+ hours in it with almost no drain.

Get some cheap micro bookshelves, a box, and you've got an awsome boombox for cheap!

Good luck!

BILL

edit to add: I am in no way shape or form an expert.

I second the T-Amp, though you can get a DIY version from http://www.41hz.com. It should be more efficient than the opamp based system, and thus not strain the battery as much.

Rick how does that sound? Screw the t-amp to a board and mount the speakers to it. What kind of 12V battery did you use? Can you give me a link?

i bought the cheapest car sized battery I could find at walmart. It was 20 bucks. 12V 275 amp lawn and tractor battery. Trickle chargers are cheap too, so I figure once this dies, I can charge if for a night and use it'll be charged for another 100 hours or so. I'm still on the same initial charge.

I'd love to hear abou those 41Hz amps. Are they better than the T-amp? and are the compnents they send you any good? or would they have to be replaced too?

whatever....

B

You guys are not even close to a "Boom box" which I thought was the goal but more "portable system".Any car battery no matter how small is heavy and that right there takes it out of the realm of boom box which by the classic definition is something easily or maybe notr so easily but possbly carried from one point to another while playing.While I was thinking how to get there using D-Cells (as in any true boom box I have ever owned) which are readily available at any convenience,beach or camp store.

Even a small weight gets heavy fast and a long truck down the boardwalk or to a campsite or the canoe with a 30 pound behemoth no joke (why all my coolers have wheels ).The T-amp solution while a good one is more Stationary Battery Operated System than it is truly portable.

If weight is then no consequence disregard the suggestion of 3/8 plywood and go straight up to a full 1/2 inch marine grade plywood.heavy but indestructable and with three coats of Marine spar Varnish damn near element proof (get the one with UV inhibitors).A couple of Pro Speaker Cabinet handles on the sides would also be a good idea for moving the beast.
You also want to consider adding a tap to your motor vehicle battery recharging system and/or upping the current output of the alternator to handle charging two batteries (internal vehicle battery in parallel with the external amplifier battery) so when you drain the one in the amp you can plug it in to the vehicle and recharge it.

inverters are real cheap too......and a great tool to have if a battery's gotta get charged.

I'm with you on the D-cell battery solution to weight, but you'd need a lot to run an amp for a long time at listening level.......and if they run dry, you've got to shell out 20 bucks at the nearest gas station to replace them.....


I'll bet you can get a small tractor battery or a sealed battery that would be equivalent in weight and output.

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that is how it has always been done man.Load it,drain it,reload it

Until mine fell off a roof top and detonated on the ground I had to load it three times a week at a cost of $30


Not real comfy with a digital amp AND a switching supply in combination but for outdoor use maybe just fine.I always try to aim for the best solution within a price range if building something wanting to better what is commercially available or at least have features i find lacking on what is offered and a chip amp done right will compete with any mid level stereo even if that stero home based.
Combined with a couple of full rangers and maybe a supertweeter tacked on (piezo horn crossed in at around 12-15 khz with a simpe resistor filter) would go a long way towards true "high fidelity" while still remaining small and light with all the weight being the D-Cells.Still minor all things considered.

12 D-Cells and a bridged amp which is how all autosound systems do it to get high power from a limited voltage supply combined with a front end and tone controls I am thinking a "curb weight" of around 6.0 lbs with 4.0 lbs possible

This is what we need to design.

A vacuum tube amp boombox with a compact voigt tube and Fostex drivers. All connected to a Minimac with an external soundcard. all running off D-cell batteries.

get on it.

Fostex drivers IS what I would use but ported.Tubes suck at these voltages unless there is more current available but no reason why pencil tubes could not be used if someone wanted to-maybe a hybrid tube/discrete the external soundcard is any USB DAC.

I realise you were just being a wise guy but anything wanting to be done can be if you plan accordingly and pay attention to what is available.There really is no limit other than cost and/or skill level to what can be made.

Full blown tube gear in a portable ? time to brush up on you voltage multiplier skills and look at Stve Benches web pages.old news man.

Im just thinking of using this thing as a backyard boombox or beach unit. I could carry 20lbs a couple of hundred feet. I think the Sonic T-amp with a rechargeable 12V power supply would work. I would like to get 8hrs of use each time and get good non clipping sound out of them.

Anyone have a link for the battery?
Is there a special cable I would need to hook up the batter to the amp?
What car speakers would you recommend for this application?