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stahlm004443 28th August 2011 01:57 PM

may have jumped in at the deep in here...
so, ive just come back from a festival here in the uk and it was amazing apart from the lack of music at the camp site.
so i took it into my own hands to build a boom box. ive been looking around here, especially the boominator thread (very helpful) to get ideas and last night just went for it and bought some component speakers, an amp and 2 batterys.
ill put the links at the bottom.
when they arrive all i will be doing is then constructing the box. but i have a few questions i neeed to clear up first:

- will all that gear i have bought work togeather and
- will it even sound any good
- how long will the batterys last
- shound the box have ports or not
- do i need to put any dividers in the box between the speakers or tweeters.

as you can tell im pretty much a complete noob! :/

any help at all would be wonderful

thanks a bunch, matt

lepai amp

jbl component speakers

batterys x2

DYNABLASTERTUNERS 28th August 2011 04:14 PM

those are Freeair I think, so you need a big box for bass :P

better that you bought two Visaton BG20 or some wideranger that are more efficient and don't require a big box :)

stahlm004443 28th August 2011 04:18 PM

I'm not really that worried about deep bass, just plenty of mid and as much volume as possible. :)

2litre 28th August 2011 07:48 PM

I'm a tinkerer so I've come up with concoctions like this in my past.
That being said:

1. As far as I can tell all components should work together.
2. It will probably sound OK. Box size, rigidity and damping will all help it sound better.
3. I don't know electrical math but someone here should be abble to give an estimate, for each one and for two in series.
4. Those woofers probably have a high-ish Qts so sealed is probably the best option. As DBT mentioned, they're designed more for free air (car doors and rear decks with lots of space behind). I'd start with 1cuft at a minimum per woofer.
5. Divide the woofers, 1 cuft (28l) per woofer. The tweeters appear to be sealed. If so you don't need a seperate space for them, so being in the same enclosure as the woofer should be fine. And I'd keep them as close to the woofers as you can when mounting.


tomi 28th August 2011 08:11 PM

Looks from the blurb on Ebay like the tweeters have a built-in crossover - probably just a single capacitor. When they arrive, measure accross one with a multimeter on Ohms range - if it reads open circuit (very high or out-of-range) then it has some form of network built in.
Finally, when you get it to your next fessie, make sure that the security goons don't try to confiscate it!

stahlm004443 28th August 2011 08:24 PM

thankyou very much, that is a big help.

this is sort of a first try kind of thing, i will probably end up making a better one with bigger and better woofers and what not at some point.

so MDF or PLY? im probably only going to use 10mm maybe 12mm because weight is a big factor in this build.

TerryO 28th August 2011 08:25 PM

Here's Cal Weldon's answer to a portable, yet satisfactory, sound system:

Photo taken at last week's Vancouver Island DIY Fest.

Best Regards,

mashaffer 28th August 2011 08:28 PM

Unless the woofers arrive with TS parameters listed or at least a recommendation then you will have to be a test pilot. As has been mentioned the Qts is probably somewhere between high and really, really high so sealed or open back would be a consideration. If the sealed enclosure lacks any bass at all then you would want to try a much bigger box as too small of a box just strangles the bass. You may have bought yourself an opportunity to play with aperiodic (leaky sealed) enclosures. ;)

Also keep in mind that those woofers, being car speakers, were probably designed to take advantage of cabin gain which you will not have (unless you are using it in your car or the loo).

Other than the speaker design question the amp should work fine though I would not count on 20 watts before unacceptable distortion sets in. Probably about 3dB less. May or may not be loud enough to suit in an open air situation. You will just have to build it and see. You can always upgrade the amp later if need be.

Do you have a charger already? I would have been tempted to get one of those portable backup car battery boosters instead as they have the battery and built in AC charger.

karmik 28th August 2011 08:30 PM

The TA2020 Kit i bought off eBay asks for a 5-6A rated 12v power supply. With a 7Ah battery you should have some uptime. For a night at the festival you're pretty much settled.

As an advice:

Plan some sturdy handle in the speaker box, on the sides. They're very very handy with P.A. equipment and pretty common on any kind of live stage service equipment.

You might also want to consider building the amplifier directly into the boombox. If you choose to go this way, there are some on eBay that are slightly cheaper than the boxed versions.

kristleifur 28th August 2011 09:40 PM

You probably want plywood, because I'd hazard a guess that it's handles moisture better than MDF, which can swell up.

You'll definitely be able to put something together that will be a lot of fun to build and listen to ... BUT the woofers you got aren't really the easiest to work with here. Too low sensitivity, and car-audio woofers just aren't good for boomboxes. Meaning the battery life could be better, and you'll struggle to get as good bass as is possible for the same cost, weight and effort, with drivers that are built for the purpose.

I suggest you read the Boominator thread: ... It contains A LOT of information, and is highly educational. The boominator is sort of a 'perfect' outdoors boombox - really efficient and is tuned to how sound behaves outdoors. You can put something together that will be enormous fun to listen to, but I really recommend also taking a good look at an established peak. The documentation is out there.

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