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Old 14th May 2016, 05:30 PM   #1
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Join Date: Jan 2016
Default Boombox

Hi people

I'm trying once again to build a boombox. This time I thought I'd ask for some help

First of all, size. Absolute maximum dimensions are 35 cm height, 25 cm width and 10 cm depth (or 14 x 10 x 4 inches), which is around 9 liters without battery, amplifier,... This is really important because it needs to fit in my backpack (i'll mostly be taking it to school).

I need it to play as loud as possible, which is quite loud because we sit outside all the time.
It needs to have decent bass. I know this is hard to achieve with a small enclosure or when outside, but it doesn't have to go low, just loud.
Budget over sound quality also, because I'm not rich

Now I've had a few ideas.

1. A single fullrange. I think this would be my best choice, a square-faced box equipped with an 8 inch fullrange driver. Something like a Visaton BG 20, maybe even the smaller Visaton BG 17.

2. A small line arrray consisting of a lot of drivers. I had this particular driver in mind because it's small, cheap and has good specs: 2-1/2" Paper Cone Extended Range Driver 4 ohm

3. High Q woofers. This is something I am really unsure about, but I've read that sometimes putting these in a small enclosure might result in a peaky low end response. Although im probably wrong. The driver I was looking at (link) has a Qts of 1,01.

I'd really appreciate some insight all of my ideas; why they might work/ will not work at all and which one will work the best in my case.
I know I'm asking a lot, I don't have a lot of knowledge when it comes to designing speakers

Thanks a lot!
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Old 14th May 2016, 06:33 PM   #2
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Hi, I cant help with the build I'm a Noob to but god I wish we had a Parts Express in the UK ..god dash it all !
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Old 14th May 2016, 07:25 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Seeing your on a budget I will say this, its a lot harder to do well than you think.
You have no hope of building anything that will compete with an intelligent buy.

Computer Speakers - what you can get for 25 USD or 15GBP

Is an example of the sort of technology not available to the DIYer.

DIY portable boomboxes have all sorts of problems, not least
very poor charging regimes, which are complicated. Its very
easy to make mistakes in DIY boombox, IMO don't go there.

The more you understand what it takes to make a good budget
product the more you will understand at the budget end of the
market DIY is pretty much hopeless, DIY is relatively expensive.

rgds, sreten.
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Old 14th May 2016, 07:48 PM   #4
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Quote:
Originally Posted by sreten View Post
Hi,
The more you understand what it takes to make a good budget
product the more you will understand at the budget end of the
market DIY is pretty much hopeless, DIY is relatively expensive.
rgds, sreten.
Hi sreten and thank you for your reply. What I mean by budget is that I dont want to spend like 50 euros+ for a decent fullrange driver, also because it simply isn't meant for hifi purposes. I just need a portable box that goes loud.

I'm studying electronics so I have enough knowledge to figure out a charging circuit.
Like I said I'm new to designing speakers from scratch. I've pretty much decided on everything else already.

Any help is greatly appreciated!
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Old 14th May 2016, 08:09 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

On a budget, I'd have simply no interest in building such
a thing, but I would research all my available options.

I'm that sort of techocomparison geek, and look to spot a bargain.

rgds, sreten.

Last edited by sreten; 14th May 2016 at 08:15 PM.
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Old 14th May 2016, 08:28 PM   #6
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Join Date: Jul 2011
Location: UK Preston
If i was attempting one I would consider the path of least resistance.
First the voltage .. there's a lot of good stuff for 12v I helped my friend install one of these in his caravan

12v Mini Hifi Amp

He paid 11 for his its only 20w's agreed but made a fair old racket, and a pair of Alpine car speakers from a scrappy for a 10. I think .. don't quote me but car speakers are design for confined space so don't need huge volume to work

I've made a 12v supply from 2 x lithium 7.2v RC batteries and a regulator or DC-DC boost convertor for about 6 of eBay. You can get huge mA's now for not huge cost. Or if a bit of weights not a problem a 2.3 Ah alarm battery for a tenner.

Anyway hope it helps like I said I'm a Noob to so I might be talking shite
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Old 14th May 2016, 10:28 PM   #7
Erknie is offline Erknie  Australia
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Join Date: Feb 2016
A cheap solution is something like 6.5" car speakers, they are not strictly full range, many come with a coaxial tweeter eg. the JBL GT7-6 about $40 for a pair. http://www.amazon.com/JBL-GT7-6-2-Wa.../dp/B00OYGV4HE

They come with a grill which can be important on a portable device like a boombox
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Old 14th May 2016, 10:28 PM   #8
Jerms is offline Jerms  United Kingdom
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Join Date: Jun 2015
Location: High Wycombe, Bucks, UK.
Not an expert but hoping to help....

Aurasound NS3, Dayton ND90/91 or even the ND105 (with tweeter if you like HF).

They are not particularly efficient at 1st sight but they will work well with a minimum of filtering and require tiny boxes - ND90 or NS3 = 1 litre or 100x100x100mm maybe. The ND105 is more efficient and can run in under 3 litres sealed.

As for amps and source.....
A bluetooth amp can be had for say 8-12. If you want the battery to last high pass the signal or speakers to avoid wasting energy on bass too low to hear.

Cheap battery would be something like a "Magicshine 7.4V bike battery" plus a charger.... And the aforementioned boost converter. You might also build in a ground loop isolator if you need a wired input signal to the amp.

J.
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Old 14th May 2016, 10:34 PM   #9
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Quote:
Originally Posted by Jerms View Post
You might also build in a ground loop isolator if you need a wired input signal to the amp.

J.
Great idea.. hadn't thought of that
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Old 26th June 2016, 03:44 AM   #10
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Depending upon your definition of "portable", at least here in the Colonies 12 V "car batteries" may come with a carrying handle. Get the hint? Yes they weigh what maybe 10 Kg but think of the running time! Also easily charged with (of course) a car charger. Point to consider: any auto sound product will work on it. USB adaptors for your computer stuff, etc. Motorcycle battery same rationale, less mass. It is my hope that if you are going to be smoking hashish and drinking alcohol and who knows what other debauchery so far from the electricity grid, that you give due consideration to how you are to power your electronics when you listen to your EDM or whatever the hell you listen to over there
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Last edited by Soldermizer; 26th June 2016 at 03:47 AM.
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